From ebf5334f9b54f18530b1b7d50ec54ba4d875e266 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Tue, 27 Oct 2020 21:53:24 +1300
Subject: [PATCH 01/23] Add output configuration and use for version and errors

---
 index.js                           | 52 ++++++++++++++++++++++--------
 tests/command.exitOverride.test.js |  4 +--
 tests/options.version.test.js      | 10 +++---
 3 files changed, 46 insertions(+), 20 deletions(-)

diff --git a/index.js b/index.js
index 518faab67..8d26ff7a8 100644
--- a/index.js
+++ b/index.js
@@ -543,6 +543,13 @@ class Command extends EventEmitter {
     this._description = '';
     this._argsDescription = undefined;
 
+    this._outputConfiguration = {
+      log: (...args) => console.log(...args),
+      error: (...args) => console.error(...args),
+      logColumns: () => process.stdout.isTTY ? process.stdout.columns : undefined,
+      errorColumns: () => process.stderr.isTTY ? process.stderr.columns : undefined
+    };
+
     this._hidden = false;
     this._hasHelpOption = true;
     this._helpFlags = '-h, --help';
@@ -663,6 +670,23 @@ class Command extends EventEmitter {
     return this;
   }
 
+  /**
+   * WIP
+   *
+   * @param {Object} [configuration] - configuration options
+   * @return {Command|Object} `this` command for chaining, or stored configuration
+   */
+
+  configureOutput(configuration) {
+    // Do we need a getter? Could be useful for users building custom outputs,
+    // see if add other bottlenecks making less likely????
+    if (configuration === undefined) return this._outputConfiguration;
+
+    Object.assign(this._outputConfiguration, configuration);
+    // add type checking on properties and throw if incorrect????
+    return this;
+  }
+
   /**
    * Add a prepared subcommand.
    *
@@ -968,8 +992,7 @@ Read more on https://git.io/JJc0W`);
           val = option.parseArg(val, oldValue === undefined ? defaultValue : oldValue);
         } catch (err) {
           if (err.code === 'commander.optionArgumentRejected') {
-            console.error(err.message);
-            this._exit(err.exitCode, err.code, err.message);
+            this._displayError(err.exitCode, err.code, err.message);
           }
           throw err;
         }
@@ -1639,6 +1662,14 @@ Read more on https://git.io/JJc0W`);
     return this._optionValues;
   };
 
+  /**
+   * WIP
+   */
+  _displayError(exitCode, code, message) {
+    this._outputConfiguration.error(message);
+    this._exit(exitCode, code, message);
+  }
+
   /**
    * Argument `name` is missing.
    *
@@ -1648,8 +1679,7 @@ Read more on https://git.io/JJc0W`);
 
   missingArgument(name) {
     const message = `error: missing required argument '${name}'`;
-    console.error(message);
-    this._exit(1, 'commander.missingArgument', message);
+    this._displayError(1, 'commander.missingArgument', message);
   };
 
   /**
@@ -1667,8 +1697,7 @@ Read more on https://git.io/JJc0W`);
     } else {
       message = `error: option '${option.flags}' argument missing`;
     }
-    console.error(message);
-    this._exit(1, 'commander.optionMissingArgument', message);
+    this._displayError(1, 'commander.optionMissingArgument', message);
   };
 
   /**
@@ -1680,8 +1709,7 @@ Read more on https://git.io/JJc0W`);
 
   missingMandatoryOptionValue(option) {
     const message = `error: required option '${option.flags}' not specified`;
-    console.error(message);
-    this._exit(1, 'commander.missingMandatoryOptionValue', message);
+    this._displayError(1, 'commander.missingMandatoryOptionValue', message);
   };
 
   /**
@@ -1694,8 +1722,7 @@ Read more on https://git.io/JJc0W`);
   unknownOption(flag) {
     if (this._allowUnknownOption) return;
     const message = `error: unknown option '${flag}'`;
-    console.error(message);
-    this._exit(1, 'commander.unknownOption', message);
+    this._displayError(1, 'commander.unknownOption', message);
   };
 
   /**
@@ -1712,8 +1739,7 @@ Read more on https://git.io/JJc0W`);
     const fullCommand = partCommands.join(' ');
     const message = `error: unknown command '${this.args[0]}'.` +
       (this._hasHelpOption ? ` See '${fullCommand} ${this._helpLongFlag}'.` : '');
-    console.error(message);
-    this._exit(1, 'commander.unknownCommand', message);
+    this._displayError(1, 'commander.unknownCommand', message);
   };
 
   /**
@@ -1739,7 +1765,7 @@ Read more on https://git.io/JJc0W`);
     this._versionOptionName = versionOption.attributeName();
     this.options.push(versionOption);
     this.on('option:' + versionOption.name(), () => {
-      process.stdout.write(str + '\n');
+      this._outputConfiguration.log(str);
       this._exit(0, 'commander.version', str);
     });
     return this;
diff --git a/tests/command.exitOverride.test.js b/tests/command.exitOverride.test.js
index 962384a71..5f82d4c37 100644
--- a/tests/command.exitOverride.test.js
+++ b/tests/command.exitOverride.test.js
@@ -156,7 +156,7 @@ describe('.exitOverride and error details', () => {
   });
 
   test('when specify --version then throw CommanderError', () => {
-    const writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
+    const logSpy = jest.spyOn(console, 'log').mockImplementation(() => { });
     const myVersion = '1.2.3';
     const program = new commander.Command();
     program
@@ -171,7 +171,7 @@ describe('.exitOverride and error details', () => {
     }
 
     expectCommanderError(caughtErr, 0, 'commander.version', myVersion);
-    writeSpy.mockRestore();
+    logSpy.mockRestore();
   });
 
   test('when executableSubcommand succeeds then call exitOverride', async() => {
diff --git a/tests/options.version.test.js b/tests/options.version.test.js
index 863184e44..77d1daa89 100644
--- a/tests/options.version.test.js
+++ b/tests/options.version.test.js
@@ -4,18 +4,18 @@ const commander = require('../');
 
 describe('.version', () => {
   // Optional. Suppress normal output to keep test output clean.
-  let writeSpy;
+  let logSpy;
 
   beforeAll(() => {
-    writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
+    logSpy = jest.spyOn(console, 'log').mockImplementation(() => { });
   });
 
   afterEach(() => {
-    writeSpy.mockClear();
+    logSpy.mockClear();
   });
 
   afterAll(() => {
-    writeSpy.mockRestore();
+    logSpy.mockRestore();
   });
 
   test('when no .version and specify --version then unknown option error', () => {
@@ -50,7 +50,7 @@ describe('.version', () => {
     }).toThrow(myVersion);
 
     // Test output once as well, rest of tests just check the thrown message.
-    expect(writeSpy).toHaveBeenCalledWith(`${myVersion}\n`);
+    expect(logSpy).toHaveBeenCalledWith(myVersion);
   });
 
   test('when specify default long flag then display version', () => {

From 849bbbed259680175564f6c8ecc7b57f4eb478ef Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 12:08:43 +1300
Subject: [PATCH 02/23] Tests passing using write/writeErr

---
 index.js                           | 20 +++++++++++---------
 tests/command.exitOverride.test.js | 22 ++++++++++------------
 tests/options.version.test.js      | 10 +++++-----
 xxx                                | 15 +++++++++++++++
 4 files changed, 41 insertions(+), 26 deletions(-)
 create mode 100644 xxx

diff --git a/index.js b/index.js
index 8d26ff7a8..6cc4ef3e3 100644
--- a/index.js
+++ b/index.js
@@ -544,10 +544,13 @@ class Command extends EventEmitter {
     this._argsDescription = undefined;
 
     this._outputConfiguration = {
-      log: (...args) => console.log(...args),
-      error: (...args) => console.error(...args),
-      logColumns: () => process.stdout.isTTY ? process.stdout.columns : undefined,
-      errorColumns: () => process.stderr.isTTY ? process.stderr.columns : undefined
+      // "write" and "error" are choosing backwards compatibility over consistency, for now!
+      // write is used for output to stdout, and error for output to stderr.
+      // Commander only passes simple strings and does not use implicit formatting in either case.
+      write: (arg) => process.stdout.write(arg),
+      writeError: (arg) => process.stderr.write(arg),
+      columns: () => process.stdout.isTTY ? process.stdout.columns : undefined,
+      columnsError: () => process.stderr.isTTY ? process.stderr.columns : undefined
     };
 
     this._hidden = false;
@@ -683,7 +686,6 @@ class Command extends EventEmitter {
     if (configuration === undefined) return this._outputConfiguration;
 
     Object.assign(this._outputConfiguration, configuration);
-    // add type checking on properties and throw if incorrect????
     return this;
   }
 
@@ -1666,7 +1668,7 @@ Read more on https://git.io/JJc0W`);
    * WIP
    */
   _displayError(exitCode, code, message) {
-    this._outputConfiguration.error(message);
+    this._outputConfiguration.writeError(`${message}\n`);
     this._exit(exitCode, code, message);
   }
 
@@ -1765,7 +1767,7 @@ Read more on https://git.io/JJc0W`);
     this._versionOptionName = versionOption.attributeName();
     this.options.push(versionOption);
     this.on('option:' + versionOption.name(), () => {
-      this._outputConfiguration.log(str);
+      this._outputConfiguration.write(`${str}\n`);
       this._exit(0, 'commander.version', str);
     });
     return this;
@@ -1884,9 +1886,9 @@ Read more on https://git.io/JJc0W`);
     const context = { error: !!contextOptions.error };
     let write;
     if (context.error) {
-      write = (arg, ...args) => process.stderr.write(arg, ...args);
+      write = (...arg) => this._outputConfiguration.writeError(...arg);
     } else {
-      write = (arg, ...args) => process.stdout.write(arg, ...args);
+      write = (...arg) => this._outputConfiguration.write(...arg);
     }
     context.write = contextOptions.write || write;
     context.command = this;
diff --git a/tests/command.exitOverride.test.js b/tests/command.exitOverride.test.js
index 5f82d4c37..f542a5d81 100644
--- a/tests/command.exitOverride.test.js
+++ b/tests/command.exitOverride.test.js
@@ -17,18 +17,18 @@ function expectCommanderError(err, exitCode, code, message) {
 
 describe('.exitOverride and error details', () => {
   // Use internal knowledge to suppress output to keep test output clean.
-  let consoleErrorSpy;
+  let stderrSpy;
 
   beforeAll(() => {
-    consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => { });
+    stderrSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   });
 
   afterEach(() => {
-    consoleErrorSpy.mockClear();
+    stderrSpy.mockClear();
   });
 
   afterAll(() => {
-    consoleErrorSpy.mockRestore();
+    stderrSpy.mockRestore();
   });
 
   test('when specify unknown program option then throw CommanderError', () => {
@@ -43,7 +43,7 @@ describe('.exitOverride and error details', () => {
       caughtErr = err;
     }
 
-    expect(consoleErrorSpy).toHaveBeenCalled();
+    expect(stderrSpy).toHaveBeenCalled();
     expectCommanderError(caughtErr, 1, 'commander.unknownOption', "error: unknown option '-m'");
   });
 
@@ -61,7 +61,7 @@ describe('.exitOverride and error details', () => {
       caughtErr = err;
     }
 
-    expect(consoleErrorSpy).toHaveBeenCalled();
+    expect(stderrSpy).toHaveBeenCalled();
     expectCommanderError(caughtErr, 1, 'commander.unknownCommand', "error: unknown command 'oops'. See 'prog --help'.");
   });
 
@@ -98,7 +98,7 @@ describe('.exitOverride and error details', () => {
       caughtErr = err;
     }
 
-    expect(consoleErrorSpy).toHaveBeenCalled();
+    expect(stderrSpy).toHaveBeenCalled();
     expectCommanderError(caughtErr, 1, 'commander.optionMissingArgument', `error: option '${optionFlags}' argument missing`);
   });
 
@@ -116,7 +116,7 @@ describe('.exitOverride and error details', () => {
       caughtErr = err;
     }
 
-    expect(consoleErrorSpy).toHaveBeenCalled();
+    expect(stderrSpy).toHaveBeenCalled();
     expectCommanderError(caughtErr, 1, 'commander.missingArgument', "error: missing required argument 'arg-name'");
   });
 
@@ -138,7 +138,6 @@ describe('.exitOverride and error details', () => {
   });
 
   test('when executable subcommand and no command specified then throw CommanderError', () => {
-    const writeSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
     const program = new commander.Command();
     program
       .exitOverride()
@@ -152,11 +151,10 @@ describe('.exitOverride and error details', () => {
     }
 
     expectCommanderError(caughtErr, 1, 'commander.help', '(outputHelp)');
-    writeSpy.mockRestore();
   });
 
   test('when specify --version then throw CommanderError', () => {
-    const logSpy = jest.spyOn(console, 'log').mockImplementation(() => { });
+    const stdoutSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
     const myVersion = '1.2.3';
     const program = new commander.Command();
     program
@@ -171,7 +169,7 @@ describe('.exitOverride and error details', () => {
     }
 
     expectCommanderError(caughtErr, 0, 'commander.version', myVersion);
-    logSpy.mockRestore();
+    stdoutSpy.mockRestore();
   });
 
   test('when executableSubcommand succeeds then call exitOverride', async() => {
diff --git a/tests/options.version.test.js b/tests/options.version.test.js
index 77d1daa89..863184e44 100644
--- a/tests/options.version.test.js
+++ b/tests/options.version.test.js
@@ -4,18 +4,18 @@ const commander = require('../');
 
 describe('.version', () => {
   // Optional. Suppress normal output to keep test output clean.
-  let logSpy;
+  let writeSpy;
 
   beforeAll(() => {
-    logSpy = jest.spyOn(console, 'log').mockImplementation(() => { });
+    writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
   });
 
   afterEach(() => {
-    logSpy.mockClear();
+    writeSpy.mockClear();
   });
 
   afterAll(() => {
-    logSpy.mockRestore();
+    writeSpy.mockRestore();
   });
 
   test('when no .version and specify --version then unknown option error', () => {
@@ -50,7 +50,7 @@ describe('.version', () => {
     }).toThrow(myVersion);
 
     // Test output once as well, rest of tests just check the thrown message.
-    expect(logSpy).toHaveBeenCalledWith(myVersion);
+    expect(writeSpy).toHaveBeenCalledWith(`${myVersion}\n`);
   });
 
   test('when specify default long flag then display version', () => {
diff --git a/xxx b/xxx
new file mode 100644
index 000000000..13f285804
--- /dev/null
+++ b/xxx
@@ -0,0 +1,15 @@
+  ● program calls to addHelpText › when "before" function returns nothing then no effect
+
+    expect(jest.fn()).toHaveBeenNthCalledWith(n, ...expected)
+
+    n: 1
+    Expected: "Usage:  [options]·
+    Options:
+      -h, --help  display help for command
+    "
+    Received: "Usage:  [options]·
+    Options:
+      -h, --help  display help for command·
+    "
+
+

From c295eda6282adde3d993976a855cde0ccc6360e7 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 12:21:21 +1300
Subject: [PATCH 03/23] Suppress test output on stderr using spyon

---
 tests/args.variadic.test.js              | 15 ---------------
 tests/command.action.test.js             |  4 +---
 tests/command.allowUnknownOption.test.js |  8 ++++----
 tests/command.helpCommand.test.js        |  8 ++++----
 tests/command.helpOption.test.js         |  8 ++++----
 tests/command.unknownCommand.test.js     |  8 ++++----
 tests/command.unknownOption.test.js      |  8 ++++----
 tests/options.mandatory.test.js          | 16 ++++++++--------
 tests/options.variadic.test.js           |  4 ++--
 9 files changed, 31 insertions(+), 48 deletions(-)

diff --git a/tests/args.variadic.test.js b/tests/args.variadic.test.js
index 83c3dae82..750880175 100644
--- a/tests/args.variadic.test.js
+++ b/tests/args.variadic.test.js
@@ -3,21 +3,6 @@ const commander = require('../');
 // Testing variadic arguments. Testing all the action arguments, but could test just variadicArg.
 
 describe('variadic argument', () => {
-  // Optional. Use internal knowledge to suppress output to keep test output clean.
-  let consoleErrorSpy;
-
-  beforeAll(() => {
-    consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => { });
-  });
-
-  afterEach(() => {
-    consoleErrorSpy.mockClear();
-  });
-
-  afterAll(() => {
-    consoleErrorSpy.mockRestore();
-  });
-
   test('when no extra arguments specified for program then variadic arg is empty array', () => {
     const actionMock = jest.fn();
     const program = new commander.Command();
diff --git a/tests/command.action.test.js b/tests/command.action.test.js
index 447028933..d3b51f714 100644
--- a/tests/command.action.test.js
+++ b/tests/command.action.test.js
@@ -46,19 +46,17 @@ test('when .action on program with required argument and argument supplied then
 });
 
 test('when .action on program with required argument and argument not supplied then action not called', () => {
-  // Optional. Use internal knowledge to suppress output to keep test output clean.
-  const consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => { });
   const actionMock = jest.fn();
   const program = new commander.Command();
   program
     .exitOverride()
+    .configureOutput({ writeError: () => {} })
     .arguments('<file>')
     .action(actionMock);
   expect(() => {
     program.parse(['node', 'test']);
   }).toThrow();
   expect(actionMock).not.toHaveBeenCalled();
-  consoleErrorSpy.mockRestore();
 });
 
 // Changes made in #729 to call program action handler
diff --git a/tests/command.allowUnknownOption.test.js b/tests/command.allowUnknownOption.test.js
index cd0bca001..4425802dd 100644
--- a/tests/command.allowUnknownOption.test.js
+++ b/tests/command.allowUnknownOption.test.js
@@ -4,18 +4,18 @@ const commander = require('../');
 
 describe('allowUnknownOption', () => {
   // Optional. Use internal knowledge to suppress output to keep test output clean.
-  let consoleErrorSpy;
+  let writeErrorSpy;
 
   beforeAll(() => {
-    consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => { });
+    writeErrorSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   });
 
   afterEach(() => {
-    consoleErrorSpy.mockClear();
+    writeErrorSpy.mockClear();
   });
 
   afterAll(() => {
-    consoleErrorSpy.mockRestore();
+    writeErrorSpy.mockRestore();
   });
 
   test('when specify unknown program option then error', () => {
diff --git a/tests/command.helpCommand.test.js b/tests/command.helpCommand.test.js
index f1f769845..a42048be8 100644
--- a/tests/command.helpCommand.test.js
+++ b/tests/command.helpCommand.test.js
@@ -39,21 +39,21 @@ describe('help command listed in helpInformation', () => {
 
 describe('help command processed on correct command', () => {
   // Use internal knowledge to suppress output to keep test output clean.
-  let consoleErrorSpy;
+  let writeErrorSpy;
   let writeSpy;
 
   beforeAll(() => {
-    consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => { });
+    writeErrorSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
     writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
   });
 
   afterEach(() => {
-    consoleErrorSpy.mockClear();
+    writeErrorSpy.mockClear();
     writeSpy.mockClear();
   });
 
   afterAll(() => {
-    consoleErrorSpy.mockRestore();
+    writeErrorSpy.mockRestore();
     writeSpy.mockRestore();
   });
 
diff --git a/tests/command.helpOption.test.js b/tests/command.helpOption.test.js
index 35cff54ee..5b5a25526 100644
--- a/tests/command.helpOption.test.js
+++ b/tests/command.helpOption.test.js
@@ -2,22 +2,22 @@ const commander = require('../');
 
 describe('helpOption', () => {
   let writeSpy;
-  let consoleErrorSpy;
+  let writeErrorSpy;
 
   beforeAll(() => {
     // Optional. Suppress expected output to keep test output clean.
     writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
-    consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => { });
+    writeErrorSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   });
 
   afterEach(() => {
     writeSpy.mockClear();
-    consoleErrorSpy.mockClear();
+    writeErrorSpy.mockClear();
   });
 
   afterAll(() => {
     writeSpy.mockRestore();
-    consoleErrorSpy.mockRestore();
+    writeErrorSpy.mockRestore();
   });
 
   test('when helpOption has custom flags then custom short flag invokes help', () => {
diff --git a/tests/command.unknownCommand.test.js b/tests/command.unknownCommand.test.js
index 405625429..183d7afb0 100644
--- a/tests/command.unknownCommand.test.js
+++ b/tests/command.unknownCommand.test.js
@@ -2,18 +2,18 @@ const commander = require('../');
 
 describe('unknownOption', () => {
   // Optional. Use internal knowledge to suppress output to keep test output clean.
-  let consoleErrorSpy;
+  let writeErrorSpy;
 
   beforeAll(() => {
-    consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => { });
+    writeErrorSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   });
 
   afterEach(() => {
-    consoleErrorSpy.mockClear();
+    writeErrorSpy.mockClear();
   });
 
   afterAll(() => {
-    consoleErrorSpy.mockRestore();
+    writeErrorSpy.mockRestore();
   });
 
   test('when unknown argument in simple program then no error', () => {
diff --git a/tests/command.unknownOption.test.js b/tests/command.unknownOption.test.js
index 18dbb6896..d4b62e59e 100644
--- a/tests/command.unknownOption.test.js
+++ b/tests/command.unknownOption.test.js
@@ -4,18 +4,18 @@ const commander = require('../');
 
 describe('unknownOption', () => {
   // Optional. Use internal knowledge to suppress output to keep test output clean.
-  let consoleErrorSpy;
+  let writeErrorSpy;
 
   beforeAll(() => {
-    consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => { });
+    writeErrorSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   });
 
   afterEach(() => {
-    consoleErrorSpy.mockClear();
+    writeErrorSpy.mockClear();
   });
 
   afterAll(() => {
-    consoleErrorSpy.mockRestore();
+    writeErrorSpy.mockRestore();
   });
 
   test('when specify unknown option with subcommand and action handler then error', () => {
diff --git a/tests/options.mandatory.test.js b/tests/options.mandatory.test.js
index eaed78c71..4abb019f3 100644
--- a/tests/options.mandatory.test.js
+++ b/tests/options.mandatory.test.js
@@ -103,18 +103,18 @@ describe('required program option with mandatory value specified', () => {
 
 describe('required program option with mandatory value not specified', () => {
   // Optional. Use internal knowledge to suppress output to keep test output clean.
-  let consoleErrorSpy;
+  let writeErrorSpy;
 
   beforeAll(() => {
-    consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => { });
+    writeErrorSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   });
 
   afterEach(() => {
-    consoleErrorSpy.mockClear();
+    writeErrorSpy.mockClear();
   });
 
   afterAll(() => {
-    consoleErrorSpy.mockRestore();
+    writeErrorSpy.mockRestore();
   });
 
   test('when program has required option not specified then error', () => {
@@ -185,18 +185,18 @@ describe('required command option with mandatory value specified', () => {
 
 describe('required command option with mandatory value not specified', () => {
   // Optional. Use internal knowledge to suppress output to keep test output clean.
-  let consoleErrorSpy;
+  let writeErrorSpy;
 
   beforeAll(() => {
-    consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => { });
+    writeErrorSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   });
 
   afterEach(() => {
-    consoleErrorSpy.mockClear();
+    writeErrorSpy.mockClear();
   });
 
   afterAll(() => {
-    consoleErrorSpy.mockRestore();
+    writeErrorSpy.mockRestore();
   });
 
   test('when command has required value not specified then error', () => {
diff --git a/tests/options.variadic.test.js b/tests/options.variadic.test.js
index f06002ec1..c414cdb1f 100644
--- a/tests/options.variadic.test.js
+++ b/tests/options.variadic.test.js
@@ -3,7 +3,7 @@ const commander = require('../');
 describe('variadic option with required value', () => {
   test('when variadic with value missing then error', () => {
     // Optional. Use internal knowledge to suppress output to keep test output clean.
-    const consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => { });
+    const writeErrorSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
 
     const program = new commander.Command();
     program
@@ -14,7 +14,7 @@ describe('variadic option with required value', () => {
       program.parse(['--required'], { from: 'user' });
     }).toThrow();
 
-    consoleErrorSpy.mockRestore();
+    writeErrorSpy.mockRestore();
   });
 
   test('when variadic with one value then set in array', () => {

From 0d82720666f90f477f6ef06e54ce3b10f3063967 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 13:13:24 +1300
Subject: [PATCH 04/23] Accurately set help columns for stdout/stderr

---
 index.js                   | 16 ++++++++++------
 tests/help.columns.test.js | 22 ----------------------
 typings/index.d.ts         |  2 +-
 3 files changed, 11 insertions(+), 29 deletions(-)
 delete mode 100644 tests/help.columns.test.js

diff --git a/index.js b/index.js
index 6cc4ef3e3..c18e0914b 100644
--- a/index.js
+++ b/index.js
@@ -12,7 +12,7 @@ const fs = require('fs');
 // Although this is a class, methods are static in style to allow override using subclass or just functions.
 class Help {
   constructor() {
-    this.columns = process.stdout.columns || 80;
+    this.columns = undefined;
     this.sortSubcommands = false;
     this.sortOptions = false;
   }
@@ -243,7 +243,7 @@ class Help {
 
   formatHelp(cmd, helper) {
     const termWidth = helper.padWidth(cmd, helper);
-    const columns = helper.columns;
+    const columns = helper.columns || 80;
     const itemIndentWidth = 2;
     const itemSeparatorWidth = 2;
     // itemIndent term itemSeparator description
@@ -549,8 +549,8 @@ class Command extends EventEmitter {
       // Commander only passes simple strings and does not use implicit formatting in either case.
       write: (arg) => process.stdout.write(arg),
       writeError: (arg) => process.stderr.write(arg),
-      columns: () => process.stdout.isTTY ? process.stdout.columns : undefined,
-      columnsError: () => process.stderr.isTTY ? process.stderr.columns : undefined
+      getColumns: () => process.stdout.isTTY ? process.stdout.columns : undefined,
+      getErrorColumns: () => process.stderr.isTTY ? process.stderr.columns : undefined
     };
 
     this._hidden = false;
@@ -1869,11 +1869,15 @@ Read more on https://git.io/JJc0W`);
   /**
    * Return program help documentation.
    *
+   * @param {{ error: boolean }} [contextOptions] - pass {error:true} to wrap for stderr instead of stdout
    * @return {string}
    */
 
-  helpInformation() {
+  helpInformation(contextOptions) {
     const helper = this.createHelp();
+    if (helper.columns === undefined) {
+      helper.columns = (contextOptions && contextOptions.error) ? this._outputConfiguration.getErrorColumns() : this._outputConfiguration.getColumns();
+    }
     return helper.formatHelp(this, helper);
   };
 
@@ -1921,7 +1925,7 @@ Read more on https://git.io/JJc0W`);
     groupListeners.slice().reverse().forEach(command => command.emit('beforeAllHelp', context));
     this.emit('beforeHelp', context);
 
-    let helpInformation = this.helpInformation();
+    let helpInformation = this.helpInformation(context);
     if (deprecatedCallback) {
       helpInformation = deprecatedCallback(helpInformation);
       if (typeof helpInformation !== 'string' && !Buffer.isBuffer(helpInformation)) {
diff --git a/tests/help.columns.test.js b/tests/help.columns.test.js
deleted file mode 100644
index cecaa4186..000000000
--- a/tests/help.columns.test.js
+++ /dev/null
@@ -1,22 +0,0 @@
-const commander = require('../');
-
-// These are tests of the Help class, not of the Command help.
-// There is some overlap with the higher level Command tests (which predate Help).
-
-describe('columns', () => {
-  test('when default then columns from stdout', () => {
-    const hold = process.stdout.columns;
-    process.stdout.columns = 123;
-    const program = new commander.Command();
-    const helper = program.createHelp();
-    expect(helper.columns).toEqual(123);
-    process.stdout.columns = hold;
-  });
-
-  test('when configure columns then value from user', () => {
-    const program = new commander.Command();
-    program.configureHelp({ columns: 321 });
-    const helper = program.createHelp();
-    expect(helper.columns).toEqual(321);
-  });
-});
diff --git a/typings/index.d.ts b/typings/index.d.ts
index 78a695da1..e7ef9f6e8 100644
--- a/typings/index.d.ts
+++ b/typings/index.d.ts
@@ -77,7 +77,7 @@ declare namespace commander {
 
   interface Help {
     /** output columns, long lines are wrapped to fit */
-    columns: number;
+    columns?: number;
     sortSubcommands: boolean;
     sortOptions: boolean;
 

From ab1e0ceeea2ed28e994ac4d2c0ec9c16e131c20a Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 13:21:03 +1300
Subject: [PATCH 05/23] Remove bogus file

---
 xxx | 15 ---------------
 1 file changed, 15 deletions(-)
 delete mode 100644 xxx

diff --git a/xxx b/xxx
deleted file mode 100644
index 13f285804..000000000
--- a/xxx
+++ /dev/null
@@ -1,15 +0,0 @@
-  ● program calls to addHelpText › when "before" function returns nothing then no effect
-
-    expect(jest.fn()).toHaveBeenNthCalledWith(n, ...expected)
-
-    n: 1
-    Expected: "Usage:  [options]·
-    Options:
-      -h, --help  display help for command
-    "
-    Received: "Usage:  [options]·
-    Options:
-      -h, --help  display help for command·
-    "
-
-

From 95c3153e14907ccd41c77942efab0524aea3fd64 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 13:25:07 +1300
Subject: [PATCH 06/23] Tidy comments

---
 index.js | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/index.js b/index.js
index c18e0914b..7a939ca0f 100644
--- a/index.js
+++ b/index.js
@@ -544,11 +544,9 @@ class Command extends EventEmitter {
     this._argsDescription = undefined;
 
     this._outputConfiguration = {
-      // "write" and "error" are choosing backwards compatibility over consistency, for now!
-      // write is used for output to stdout, and error for output to stderr.
-      // Commander only passes simple strings and does not use implicit formatting in either case.
       write: (arg) => process.stdout.write(arg),
       writeError: (arg) => process.stderr.write(arg),
+      // columns is used for wrapping the help
       getColumns: () => process.stdout.isTTY ? process.stdout.columns : undefined,
       getErrorColumns: () => process.stderr.isTTY ? process.stderr.columns : undefined
     };
@@ -681,8 +679,6 @@ class Command extends EventEmitter {
    */
 
   configureOutput(configuration) {
-    // Do we need a getter? Could be useful for users building custom outputs,
-    // see if add other bottlenecks making less likely????
     if (configuration === undefined) return this._outputConfiguration;
 
     Object.assign(this._outputConfiguration, configuration);

From 9f3efe2f8ae255299b985b235cc6070d49a816f6 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 15:01:28 +1300
Subject: [PATCH 07/23] Only using single argument to write, simplify
 declaration to match

---
 index.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/index.js b/index.js
index 7a939ca0f..6e1c20f81 100644
--- a/index.js
+++ b/index.js
@@ -1886,9 +1886,9 @@ Read more on https://git.io/JJc0W`);
     const context = { error: !!contextOptions.error };
     let write;
     if (context.error) {
-      write = (...arg) => this._outputConfiguration.writeError(...arg);
+      write = (arg) => this._outputConfiguration.writeError(arg);
     } else {
-      write = (...arg) => this._outputConfiguration.write(...arg);
+      write = (arg) => this._outputConfiguration.write(arg);
     }
     context.write = contextOptions.write || write;
     context.command = this;

From 6a3eadfa440e0460e1cbdc5edace8aa9a50fb19a Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 18:40:18 +1300
Subject: [PATCH 08/23] Add tests for configureOutput write and writeError

---
 tests/command.configureOutput.test.js | 108 ++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 tests/command.configureOutput.test.js

diff --git a/tests/command.configureOutput.test.js b/tests/command.configureOutput.test.js
new file mode 100644
index 000000000..013d9acdf
--- /dev/null
+++ b/tests/command.configureOutput.test.js
@@ -0,0 +1,108 @@
+const commander = require('../');
+
+test('when default writeError() then error on stderr', () => {
+  const writeSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
+  const program = new commander.Command();
+  program.exitOverride();
+
+  try {
+    program.parse(['--unknown'], { from: 'user' });
+  } catch (err) {
+  }
+
+  expect(writeSpy).toHaveBeenCalledTimes(1);
+  writeSpy.mockRestore();
+});
+
+test('when custom writeError() then error on custom output', () => {
+  const writeSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
+  const customWrite = jest.fn();
+  const program = new commander.Command();
+  program
+    .exitOverride()
+    .configureOutput({ writeError: customWrite });
+
+  try {
+    program.parse(['--unknown'], { from: 'user' });
+  } catch (err) {
+  }
+
+  expect(writeSpy).toHaveBeenCalledTimes(0);
+  expect(customWrite).toHaveBeenCalledTimes(1);
+  writeSpy.mockRestore();
+});
+
+test('when default write() then version on stdout', () => {
+  const writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
+  const program = new commander.Command();
+  program
+    .exitOverride()
+    .version('1.2.3');
+
+  expect(() => {
+    program.parse(['--version'], { from: 'user' });
+  }).toThrow();
+
+  expect(writeSpy).toHaveBeenCalledTimes(1);
+  writeSpy.mockRestore();
+});
+
+test('when custom write() then version on custom output', () => {
+  const writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
+  const customWrite = jest.fn();
+  const program = new commander.Command();
+  program
+    .exitOverride()
+    .version('1.2.3')
+    .configureOutput({ write: customWrite });
+
+  expect(() => {
+    program.parse(['--version'], { from: 'user' });
+  }).toThrow();
+
+  expect(writeSpy).toHaveBeenCalledTimes(0);
+  expect(customWrite).toHaveBeenCalledTimes(1);
+  writeSpy.mockRestore();
+});
+
+test('when default write() then help on stdout', () => {
+  const writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
+  const program = new commander.Command();
+  program.outputHelp();
+
+  expect(writeSpy).toHaveBeenCalledTimes(1);
+  writeSpy.mockRestore();
+});
+
+test('when custom write() then help error on stdout', () => {
+  const writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
+  const customWrite = jest.fn();
+  const program = new commander.Command();
+  program.configureOutput({ write: customWrite });
+  program.outputHelp();
+
+  expect(writeSpy).toHaveBeenCalledTimes(0);
+  expect(customWrite).toHaveBeenCalledTimes(1);
+  writeSpy.mockRestore();
+});
+
+test('when default writeError then help error on stderr', () => {
+  const writeSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
+  const program = new commander.Command();
+  program.outputHelp({ error: true });
+
+  expect(writeSpy).toHaveBeenCalledTimes(1);
+  writeSpy.mockRestore();
+});
+
+test('when custom writeError then help error on stderr', () => {
+  const writeSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
+  const customWrite = jest.fn();
+  const program = new commander.Command();
+  program.configureOutput({ writeError: customWrite });
+  program.outputHelp({ error: true });
+
+  expect(writeSpy).toHaveBeenCalledTimes(0);
+  expect(customWrite).toHaveBeenCalledTimes(1);
+  writeSpy.mockRestore();
+});

From b191033f2a16b680b8361a27b072de66818e09cd Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 19:42:27 +1300
Subject: [PATCH 09/23] Add tests for configureOutput getColumns and
 getErrorColumns

---
 tests/command.configureOutput.test.js | 109 +++++++++++++++++++++++++-
 1 file changed, 107 insertions(+), 2 deletions(-)

diff --git a/tests/command.configureOutput.test.js b/tests/command.configureOutput.test.js
index 013d9acdf..95dfb53fd 100644
--- a/tests/command.configureOutput.test.js
+++ b/tests/command.configureOutput.test.js
@@ -74,7 +74,7 @@ test('when default write() then help on stdout', () => {
   writeSpy.mockRestore();
 });
 
-test('when custom write() then help error on stdout', () => {
+test('when custom write() then help error on custom output', () => {
   const writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
   const customWrite = jest.fn();
   const program = new commander.Command();
@@ -95,7 +95,7 @@ test('when default writeError then help error on stderr', () => {
   writeSpy.mockRestore();
 });
 
-test('when custom writeError then help error on stderr', () => {
+test('when custom writeError then help error on custom output', () => {
   const writeSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   const customWrite = jest.fn();
   const program = new commander.Command();
@@ -106,3 +106,108 @@ test('when custom writeError then help error on stderr', () => {
   expect(customWrite).toHaveBeenCalledTimes(1);
   writeSpy.mockRestore();
 });
+
+test('when default getColumns then help columns from stdout', () => {
+  const expectedColumns = 123;
+  const holdIsTTY = process.stdout.isTTY;
+  const holdColumns = process.stdout.columns;
+  let helpColumns;
+
+  process.stderr.isTTY = true;
+  process.stdout.columns = expectedColumns;
+  process.stdout.isTTY = true;
+  const program = new commander.Command();
+  program
+    .configureHelp({
+      formatHelp: (cmd, helper) => {
+        helpColumns = helper.columns;
+        return '';
+      }
+    });
+  program.outputHelp();
+
+  expect(helpColumns).toBe(expectedColumns);
+  process.stdout.columns = holdColumns;
+  process.stdout.isTTY = holdIsTTY;
+});
+
+test('when custom getColumns then help columns custom', () => {
+  const expectedColumns = 123;
+  let helpColumns;
+
+  const program = new commander.Command();
+  program
+    .configureHelp({
+      formatHelp: (cmd, helper) => {
+        helpColumns = helper.columns;
+        return '';
+      }
+    }).configureOutput({
+      getColumns: () => expectedColumns
+    });
+  program.outputHelp();
+
+  expect(helpColumns).toBe(expectedColumns);
+});
+
+test('when default getErrorColumns then help error columns from stderr', () => {
+  const expectedColumns = 123;
+  const holdIsTTY = process.stderr.isTTY;
+  const holdColumns = process.stderr.columns;
+  let helpColumns;
+
+  process.stderr.isTTY = true;
+  process.stderr.columns = expectedColumns;
+  const program = new commander.Command();
+  program
+    .configureHelp({
+      formatHelp: (cmd, helper) => {
+        helpColumns = helper.columns;
+        return '';
+      }
+    });
+  program.outputHelp({ error: true });
+
+  expect(helpColumns).toBe(expectedColumns);
+  process.stderr.isTTY = holdIsTTY;
+  process.stderr.columns = holdColumns;
+});
+
+test('when custom getErrorColumns then help error columns custom', () => {
+  const expectedColumns = 123;
+  let helpColumns;
+
+  const program = new commander.Command();
+  program
+    .configureHelp({
+      formatHelp: (cmd, helper) => {
+        helpColumns = helper.columns;
+        return '';
+      }
+    }).configureOutput({
+      getErrorColumns: () => expectedColumns
+    });
+  program.outputHelp({ error: true });
+
+  expect(helpColumns).toBe(expectedColumns);
+});
+
+test('when custom getColumns and configureHelp:columns then help columns from configureHelp', () => {
+  const expectedColumns = 123;
+  let helpColumns;
+
+  const program = new commander.Command();
+  program
+    .configureHelp({
+      formatHelp: (cmd, helper) => {
+        helpColumns = helper.columns;
+        return '';
+      },
+      columns: expectedColumns
+    }).configureOutput({
+      getColumns: () => 999
+    });
+  program.outputHelp();
+
+  expect(helpColumns).toBe(expectedColumns);
+});

From 627f31045aa2f42da3f4354b626a203a16d7bfc5 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 19:58:08 +1300
Subject: [PATCH 10/23] Add error case too

---
 tests/command.configureOutput.test.js | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tests/command.configureOutput.test.js b/tests/command.configureOutput.test.js
index 95dfb53fd..1502f15ca 100644
--- a/tests/command.configureOutput.test.js
+++ b/tests/command.configureOutput.test.js
@@ -211,3 +211,23 @@ test('when custom getColumns and configureHelp:columns then help columns from co
 
   expect(helpColumns).toBe(expectedColumns);
 });
+
+test('when custom getErrorColumns and configureHelp:columns then help error columns from configureHelp', () => {
+  const expectedColumns = 123;
+  let helpColumns;
+
+  const program = new commander.Command();
+  program
+    .configureHelp({
+      formatHelp: (cmd, helper) => {
+        helpColumns = helper.columns;
+        return '';
+      },
+      columns: expectedColumns
+    }).configureOutput({
+      getErrorColumns: () => 999
+    });
+  program.outputHelp({ error: true });
+
+  expect(helpColumns).toBe(expectedColumns);
+});

From 02f5b44f85dd0d703055d53103272c99fafe0b98 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 21:58:28 +1300
Subject: [PATCH 11/23] Use configureOutput instead of jest.spyon for some
 tests

---
 tests/options.variadic.test.js |  6 +-----
 tests/options.version.test.js  | 39 ++++++++++++++++++----------------
 2 files changed, 22 insertions(+), 23 deletions(-)

diff --git a/tests/options.variadic.test.js b/tests/options.variadic.test.js
index c414cdb1f..d531c6648 100644
--- a/tests/options.variadic.test.js
+++ b/tests/options.variadic.test.js
@@ -2,19 +2,15 @@ const commander = require('../');
 
 describe('variadic option with required value', () => {
   test('when variadic with value missing then error', () => {
-    // Optional. Use internal knowledge to suppress output to keep test output clean.
-    const writeErrorSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
-
     const program = new commander.Command();
     program
       .exitOverride()
+      .configureOutput({ writeError: jest.fn() })
       .option('-r,--required <value...>');
 
     expect(() => {
       program.parse(['--required'], { from: 'user' });
     }).toThrow();
-
-    writeErrorSpy.mockRestore();
   });
 
   test('when variadic with one value then set in array', () => {
diff --git a/tests/options.version.test.js b/tests/options.version.test.js
index 863184e44..1036ff984 100644
--- a/tests/options.version.test.js
+++ b/tests/options.version.test.js
@@ -3,21 +3,6 @@ const commander = require('../');
 // Test .version. Using exitOverride to check behaviour (instead of mocking process.exit).
 
 describe('.version', () => {
-  // Optional. Suppress normal output to keep test output clean.
-  let writeSpy;
-
-  beforeAll(() => {
-    writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
-  });
-
-  afterEach(() => {
-    writeSpy.mockClear();
-  });
-
-  afterAll(() => {
-    writeSpy.mockRestore();
-  });
-
   test('when no .version and specify --version then unknown option error', () => {
     const errorMessage = 'unknownOption';
     const program = new commander.Command();
@@ -40,29 +25,32 @@ describe('.version', () => {
 
   test('when specify default short flag then display version', () => {
     const myVersion = '1.2.3';
+    const writeMock = jest.fn();
     const program = new commander.Command();
     program
       .exitOverride()
+      .configureOutput({ write: writeMock })
       .version(myVersion);
 
     expect(() => {
       program.parse(['node', 'test', '-V']);
     }).toThrow(myVersion);
-
-    // Test output once as well, rest of tests just check the thrown message.
-    expect(writeSpy).toHaveBeenCalledWith(`${myVersion}\n`);
+    expect(writeMock).toHaveBeenCalledWith(`${myVersion}\n`);
   });
 
   test('when specify default long flag then display version', () => {
     const myVersion = '1.2.3';
+    const writeMock = jest.fn();
     const program = new commander.Command();
     program
       .exitOverride()
+      .configureOutput({ write: writeMock })
       .version(myVersion);
 
     expect(() => {
       program.parse(['node', 'test', '--version']);
     }).toThrow(myVersion);
+    expect(writeMock).toHaveBeenCalledWith(`${myVersion}\n`);
   });
 
   test('when default .version then helpInformation includes default version help', () => {
@@ -79,50 +67,62 @@ describe('.version', () => {
 
   test('when specify custom short flag then display version', () => {
     const myVersion = '1.2.3';
+    const writeMock = jest.fn();
     const program = new commander.Command();
     program
       .exitOverride()
+      .configureOutput({ write: writeMock })
       .version(myVersion, '-r, --revision');
 
     expect(() => {
       program.parse(['node', 'test', '-r']);
     }).toThrow(myVersion);
+    expect(writeMock).toHaveBeenCalledWith(`${myVersion}\n`);
   });
 
   test('when specify just custom short flag then display version', () => {
     const myVersion = '1.2.3';
+    const writeMock = jest.fn();
     const program = new commander.Command();
     program
       .exitOverride()
+      .configureOutput({ write: writeMock })
       .version(myVersion, '-r');
 
     expect(() => {
       program.parse(['node', 'test', '-r']);
     }).toThrow(myVersion);
+    expect(writeMock).toHaveBeenCalledWith(`${myVersion}\n`);
   });
 
   test('when specify custom long flag then display version', () => {
     const myVersion = '1.2.3';
+    const writeMock = jest.fn();
     const program = new commander.Command();
     program
       .exitOverride()
+      .configureOutput({ write: writeMock })
       .version(myVersion, '-r, --revision');
 
     expect(() => {
       program.parse(['node', 'test', '--revision']);
     }).toThrow(myVersion);
+    expect(writeMock).toHaveBeenCalledWith(`${myVersion}\n`);
   });
 
   test('when specify just custom long flag then display version', () => {
     const myVersion = '1.2.3';
+    const writeMock = jest.fn();
     const program = new commander.Command();
     program
       .exitOverride()
+      .configureOutput({ write: writeMock })
       .version(myVersion, '--revision');
 
     expect(() => {
       program.parse(['node', 'test', '--revision']);
     }).toThrow(myVersion);
+    expect(writeMock).toHaveBeenCalledWith(`${myVersion}\n`);
   });
 
   test('when custom .version then helpInformation includes custom version help', () => {
@@ -154,9 +154,11 @@ describe('.version', () => {
 
   test('when have .version+version and specify --version then version displayed', () => {
     const myVersion = '1.2.3';
+    const writeMock = jest.fn();
     const program = new commander.Command();
     program
       .exitOverride()
+      .configureOutput({ write: writeMock })
       .version(myVersion)
       .command('version')
       .action(() => {});
@@ -164,6 +166,7 @@ describe('.version', () => {
     expect(() => {
       program.parse(['node', 'test', '--version']);
     }).toThrow(myVersion);
+    expect(writeMock).toHaveBeenCalledWith(`${myVersion}\n`);
   });
 
   test('when specify version then can get version', () => {

From d89c91874730dbc3841457659fb826382912d9f5 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 21:59:44 +1300
Subject: [PATCH 12/23] Add configureOutput to chain tests

---
 tests/command.chain.test.js | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tests/command.chain.test.js b/tests/command.chain.test.js
index 5979c3ab0..9918dae0c 100644
--- a/tests/command.chain.test.js
+++ b/tests/command.chain.test.js
@@ -135,4 +135,10 @@ describe('Command methods that should return this for chaining', () => {
     const result = program.configureHelp({ });
     expect(result).toBe(program);
   });
+
+  test('when call .configureOutput() then returns this', () => {
+    const program = new Command();
+    const result = program.configureOutput({ });
+    expect(result).toBe(program);
+  });
 });

From 3477e7e28675598479525a983b7a9edb322213e2 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 31 Oct 2020 22:15:53 +1300
Subject: [PATCH 13/23] Add set/get test for configureOutput

---
 tests/command.configureOutput.test.js | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tests/command.configureOutput.test.js b/tests/command.configureOutput.test.js
index 1502f15ca..7de9fa4c3 100644
--- a/tests/command.configureOutput.test.js
+++ b/tests/command.configureOutput.test.js
@@ -231,3 +231,15 @@ test('when custom getErrorColumns and configureHelp:columns then help error colu
 
   expect(helpColumns).toBe(expectedColumns);
 });
+
+test('when set configureOutput then get configureOutput', () => {
+  const outputOptions = {
+    write: jest.fn(),
+    writeError: jest.fn(),
+    getColumns: jest.fn(),
+    getErrorColumns: jest.fn()
+  };
+  const program = new commander.Command();
+  program.configureOutput(outputOptions);
+  expect(program.configureOutput()).toEqual(outputOptions);
+});

From a0b1db7b00e5cd04073dc353aed7e9199efb368d Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 7 Nov 2020 16:36:52 +1300
Subject: [PATCH 14/23] Rename routines with symmetrical out/err

---
 index.js                              | 18 +++++------
 tests/command.action.test.js          |  2 +-
 tests/command.configureOutput.test.js | 44 +++++++++++++--------------
 tests/options.variadic.test.js        |  2 +-
 tests/options.version.test.js         | 14 ++++-----
 5 files changed, 40 insertions(+), 40 deletions(-)

diff --git a/index.js b/index.js
index 6e1c20f81..94e256469 100644
--- a/index.js
+++ b/index.js
@@ -544,11 +544,11 @@ class Command extends EventEmitter {
     this._argsDescription = undefined;
 
     this._outputConfiguration = {
-      write: (arg) => process.stdout.write(arg),
-      writeError: (arg) => process.stderr.write(arg),
+      writeOut: (arg) => process.stdout.write(arg),
+      writeErr: (arg) => process.stderr.write(arg),
       // columns is used for wrapping the help
-      getColumns: () => process.stdout.isTTY ? process.stdout.columns : undefined,
-      getErrorColumns: () => process.stderr.isTTY ? process.stderr.columns : undefined
+      getOutColumns: () => process.stdout.isTTY ? process.stdout.columns : undefined,
+      getErrColumns: () => process.stderr.isTTY ? process.stderr.columns : undefined
     };
 
     this._hidden = false;
@@ -1664,7 +1664,7 @@ Read more on https://git.io/JJc0W`);
    * WIP
    */
   _displayError(exitCode, code, message) {
-    this._outputConfiguration.writeError(`${message}\n`);
+    this._outputConfiguration.writeErr(`${message}\n`);
     this._exit(exitCode, code, message);
   }
 
@@ -1763,7 +1763,7 @@ Read more on https://git.io/JJc0W`);
     this._versionOptionName = versionOption.attributeName();
     this.options.push(versionOption);
     this.on('option:' + versionOption.name(), () => {
-      this._outputConfiguration.write(`${str}\n`);
+      this._outputConfiguration.writeOut(`${str}\n`);
       this._exit(0, 'commander.version', str);
     });
     return this;
@@ -1872,7 +1872,7 @@ Read more on https://git.io/JJc0W`);
   helpInformation(contextOptions) {
     const helper = this.createHelp();
     if (helper.columns === undefined) {
-      helper.columns = (contextOptions && contextOptions.error) ? this._outputConfiguration.getErrorColumns() : this._outputConfiguration.getColumns();
+      helper.columns = (contextOptions && contextOptions.error) ? this._outputConfiguration.getErrColumns() : this._outputConfiguration.getOutColumns();
     }
     return helper.formatHelp(this, helper);
   };
@@ -1886,9 +1886,9 @@ Read more on https://git.io/JJc0W`);
     const context = { error: !!contextOptions.error };
     let write;
     if (context.error) {
-      write = (arg) => this._outputConfiguration.writeError(arg);
+      write = (arg) => this._outputConfiguration.writeErr(arg);
     } else {
-      write = (arg) => this._outputConfiguration.write(arg);
+      write = (arg) => this._outputConfiguration.writeOut(arg);
     }
     context.write = contextOptions.write || write;
     context.command = this;
diff --git a/tests/command.action.test.js b/tests/command.action.test.js
index d3b51f714..cef18bee8 100644
--- a/tests/command.action.test.js
+++ b/tests/command.action.test.js
@@ -50,7 +50,7 @@ test('when .action on program with required argument and argument not supplied t
   const program = new commander.Command();
   program
     .exitOverride()
-    .configureOutput({ writeError: () => {} })
+    .configureOutput({ writeErr: () => {} })
     .arguments('<file>')
     .action(actionMock);
   expect(() => {
diff --git a/tests/command.configureOutput.test.js b/tests/command.configureOutput.test.js
index 7de9fa4c3..865b155f7 100644
--- a/tests/command.configureOutput.test.js
+++ b/tests/command.configureOutput.test.js
@@ -1,6 +1,6 @@
 const commander = require('../');
 
-test('when default writeError() then error on stderr', () => {
+test('when default writeErr() then error on stderr', () => {
   const writeSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   const program = new commander.Command();
   program.exitOverride();
@@ -14,13 +14,13 @@ test('when default writeError() then error on stderr', () => {
   writeSpy.mockRestore();
 });
 
-test('when custom writeError() then error on custom output', () => {
+test('when custom writeErr() then error on custom output', () => {
   const writeSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   const customWrite = jest.fn();
   const program = new commander.Command();
   program
     .exitOverride()
-    .configureOutput({ writeError: customWrite });
+    .configureOutput({ writeErr: customWrite });
 
   try {
     program.parse(['--unknown'], { from: 'user' });
@@ -54,7 +54,7 @@ test('when custom write() then version on custom output', () => {
   program
     .exitOverride()
     .version('1.2.3')
-    .configureOutput({ write: customWrite });
+    .configureOutput({ writeOut: customWrite });
 
   expect(() => {
     program.parse(['--version'], { from: 'user' });
@@ -78,7 +78,7 @@ test('when custom write() then help error on custom output', () => {
   const writeSpy = jest.spyOn(process.stdout, 'write').mockImplementation(() => { });
   const customWrite = jest.fn();
   const program = new commander.Command();
-  program.configureOutput({ write: customWrite });
+  program.configureOutput({ writeOut: customWrite });
   program.outputHelp();
 
   expect(writeSpy).toHaveBeenCalledTimes(0);
@@ -86,7 +86,7 @@ test('when custom write() then help error on custom output', () => {
   writeSpy.mockRestore();
 });
 
-test('when default writeError then help error on stderr', () => {
+test('when default writeErr then help error on stderr', () => {
   const writeSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   const program = new commander.Command();
   program.outputHelp({ error: true });
@@ -95,11 +95,11 @@ test('when default writeError then help error on stderr', () => {
   writeSpy.mockRestore();
 });
 
-test('when custom writeError then help error on custom output', () => {
+test('when custom writeErr then help error on custom output', () => {
   const writeSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => { });
   const customWrite = jest.fn();
   const program = new commander.Command();
-  program.configureOutput({ writeError: customWrite });
+  program.configureOutput({ writeErr: customWrite });
   program.outputHelp({ error: true });
 
   expect(writeSpy).toHaveBeenCalledTimes(0);
@@ -107,7 +107,7 @@ test('when custom writeError then help error on custom output', () => {
   writeSpy.mockRestore();
 });
 
-test('when default getColumns then help columns from stdout', () => {
+test('when default getOutColumns then help columns from stdout', () => {
   const expectedColumns = 123;
   const holdIsTTY = process.stdout.isTTY;
   const holdColumns = process.stdout.columns;
@@ -131,7 +131,7 @@ test('when default getColumns then help columns from stdout', () => {
   process.stdout.isTTY = holdIsTTY;
 });
 
-test('when custom getColumns then help columns custom', () => {
+test('when custom getOutColumns then help columns custom', () => {
   const expectedColumns = 123;
   let helpColumns;
 
@@ -143,14 +143,14 @@ test('when custom getColumns then help columns custom', () => {
         return '';
       }
     }).configureOutput({
-      getColumns: () => expectedColumns
+      getOutColumns: () => expectedColumns
     });
   program.outputHelp();
 
   expect(helpColumns).toBe(expectedColumns);
 });
 
-test('when default getErrorColumns then help error columns from stderr', () => {
+test('when default getErrColumns then help error columns from stderr', () => {
   const expectedColumns = 123;
   const holdIsTTY = process.stderr.isTTY;
   const holdColumns = process.stderr.columns;
@@ -173,7 +173,7 @@ test('when default getErrorColumns then help error columns from stderr', () => {
   process.stderr.columns = holdColumns;
 });
 
-test('when custom getErrorColumns then help error columns custom', () => {
+test('when custom getErrColumns then help error columns custom', () => {
   const expectedColumns = 123;
   let helpColumns;
 
@@ -185,14 +185,14 @@ test('when custom getErrorColumns then help error columns custom', () => {
         return '';
       }
     }).configureOutput({
-      getErrorColumns: () => expectedColumns
+      getErrColumns: () => expectedColumns
     });
   program.outputHelp({ error: true });
 
   expect(helpColumns).toBe(expectedColumns);
 });
 
-test('when custom getColumns and configureHelp:columns then help columns from configureHelp', () => {
+test('when custom getOutColumns and configureHelp:columns then help columns from configureHelp', () => {
   const expectedColumns = 123;
   let helpColumns;
 
@@ -205,14 +205,14 @@ test('when custom getColumns and configureHelp:columns then help columns from co
       },
       columns: expectedColumns
     }).configureOutput({
-      getColumns: () => 999
+      getOutColumns: () => 999
     });
   program.outputHelp();
 
   expect(helpColumns).toBe(expectedColumns);
 });
 
-test('when custom getErrorColumns and configureHelp:columns then help error columns from configureHelp', () => {
+test('when custom getErrColumns and configureHelp:columns then help error columns from configureHelp', () => {
   const expectedColumns = 123;
   let helpColumns;
 
@@ -225,7 +225,7 @@ test('when custom getErrorColumns and configureHelp:columns then help error colu
       },
       columns: expectedColumns
     }).configureOutput({
-      getErrorColumns: () => 999
+      getErrColumns: () => 999
     });
   program.outputHelp({ error: true });
 
@@ -234,10 +234,10 @@ test('when custom getErrorColumns and configureHelp:columns then help error colu
 
 test('when set configureOutput then get configureOutput', () => {
   const outputOptions = {
-    write: jest.fn(),
-    writeError: jest.fn(),
-    getColumns: jest.fn(),
-    getErrorColumns: jest.fn()
+    writeOut: jest.fn(),
+    writeErr: jest.fn(),
+    getOutColumns: jest.fn(),
+    getErrColumns: jest.fn()
   };
   const program = new commander.Command();
   program.configureOutput(outputOptions);
diff --git a/tests/options.variadic.test.js b/tests/options.variadic.test.js
index d531c6648..1c32e21cc 100644
--- a/tests/options.variadic.test.js
+++ b/tests/options.variadic.test.js
@@ -5,7 +5,7 @@ describe('variadic option with required value', () => {
     const program = new commander.Command();
     program
       .exitOverride()
-      .configureOutput({ writeError: jest.fn() })
+      .configureOutput({ writeErr: jest.fn() })
       .option('-r,--required <value...>');
 
     expect(() => {
diff --git a/tests/options.version.test.js b/tests/options.version.test.js
index 1036ff984..5efa5e3c4 100644
--- a/tests/options.version.test.js
+++ b/tests/options.version.test.js
@@ -29,7 +29,7 @@ describe('.version', () => {
     const program = new commander.Command();
     program
       .exitOverride()
-      .configureOutput({ write: writeMock })
+      .configureOutput({ writeOut: writeMock })
       .version(myVersion);
 
     expect(() => {
@@ -44,7 +44,7 @@ describe('.version', () => {
     const program = new commander.Command();
     program
       .exitOverride()
-      .configureOutput({ write: writeMock })
+      .configureOutput({ writeOut: writeMock })
       .version(myVersion);
 
     expect(() => {
@@ -71,7 +71,7 @@ describe('.version', () => {
     const program = new commander.Command();
     program
       .exitOverride()
-      .configureOutput({ write: writeMock })
+      .configureOutput({ writeOut: writeMock })
       .version(myVersion, '-r, --revision');
 
     expect(() => {
@@ -86,7 +86,7 @@ describe('.version', () => {
     const program = new commander.Command();
     program
       .exitOverride()
-      .configureOutput({ write: writeMock })
+      .configureOutput({ writeOut: writeMock })
       .version(myVersion, '-r');
 
     expect(() => {
@@ -101,7 +101,7 @@ describe('.version', () => {
     const program = new commander.Command();
     program
       .exitOverride()
-      .configureOutput({ write: writeMock })
+      .configureOutput({ writeOut: writeMock })
       .version(myVersion, '-r, --revision');
 
     expect(() => {
@@ -116,7 +116,7 @@ describe('.version', () => {
     const program = new commander.Command();
     program
       .exitOverride()
-      .configureOutput({ write: writeMock })
+      .configureOutput({ writeOut: writeMock })
       .version(myVersion, '--revision');
 
     expect(() => {
@@ -158,7 +158,7 @@ describe('.version', () => {
     const program = new commander.Command();
     program
       .exitOverride()
-      .configureOutput({ write: writeMock })
+      .configureOutput({ writeOut: writeMock })
       .version(myVersion)
       .command('version')
       .action(() => {});

From 015895e9ebec51297fdebe620a701ffa01fb09b9 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 7 Nov 2020 17:09:52 +1300
Subject: [PATCH 15/23] Add outputError simple code

---
 index.js                              | 11 +++++++----
 tests/command.configureOutput.test.js |  3 ++-
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/index.js b/index.js
index 94e256469..4a229d18f 100644
--- a/index.js
+++ b/index.js
@@ -544,11 +544,14 @@ class Command extends EventEmitter {
     this._argsDescription = undefined;
 
     this._outputConfiguration = {
-      writeOut: (arg) => process.stdout.write(arg),
-      writeErr: (arg) => process.stderr.write(arg),
+      // Routines for where output is going, stdout or stderr
+      writeOut: (str) => process.stdout.write(str),
+      writeErr: (str) => process.stderr.write(str),
       // columns is used for wrapping the help
       getOutColumns: () => process.stdout.isTTY ? process.stdout.columns : undefined,
-      getErrColumns: () => process.stderr.isTTY ? process.stderr.columns : undefined
+      getErrColumns: () => process.stderr.isTTY ? process.stderr.columns : undefined,
+      // routines for what is being written out
+      outputError: (str, write) => write(str) // used for displaying errors, and not used for displaying help
     };
 
     this._hidden = false;
@@ -1664,7 +1667,7 @@ Read more on https://git.io/JJc0W`);
    * WIP
    */
   _displayError(exitCode, code, message) {
-    this._outputConfiguration.writeErr(`${message}\n`);
+    this._outputConfiguration.outputError(`${message}\n`, this._outputConfiguration.writeErr);
     this._exit(exitCode, code, message);
   }
 
diff --git a/tests/command.configureOutput.test.js b/tests/command.configureOutput.test.js
index 865b155f7..e6efadcf5 100644
--- a/tests/command.configureOutput.test.js
+++ b/tests/command.configureOutput.test.js
@@ -237,7 +237,8 @@ test('when set configureOutput then get configureOutput', () => {
     writeOut: jest.fn(),
     writeErr: jest.fn(),
     getOutColumns: jest.fn(),
-    getErrColumns: jest.fn()
+    getErrColumns: jest.fn(),
+    outputError: jest.fn()
   };
   const program = new commander.Command();
   program.configureOutput(outputOptions);

From 2727d13f27d6e73607f212fe6094be2098726718 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Tue, 10 Nov 2020 22:23:17 +1300
Subject: [PATCH 16/23] Add tests for outputError

---
 tests/command.configureOutput.test.js | 29 +++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/tests/command.configureOutput.test.js b/tests/command.configureOutput.test.js
index e6efadcf5..3e9a7b80a 100644
--- a/tests/command.configureOutput.test.js
+++ b/tests/command.configureOutput.test.js
@@ -244,3 +244,32 @@ test('when set configureOutput then get configureOutput', () => {
   program.configureOutput(outputOptions);
   expect(program.configureOutput()).toEqual(outputOptions);
 });
+
+test('when custom outputErr and error then outputErr called', () => {
+  const outputError = jest.fn();
+  const program = new commander.Command();
+  program
+    .exitOverride()
+    .configureOutput({
+      outputError
+    });
+
+  expect(() => {
+    program.parse(['--unknownOption'], { from: 'user' });
+  }).toThrow();
+  expect(outputError).toHaveBeenCalledWith("error: unknown option '--unknownOption'\n", program._outputConfiguration.writeErr);
+});
+
+test('when custom outputErr and writeErr and error then outputErr passed writeErr', () => {
+  const writeErr = () => jest.fn();
+  const outputError = jest.fn();
+  const program = new commander.Command();
+  program
+    .exitOverride()
+    .configureOutput({ writeErr, outputError });
+
+  expect(() => {
+    program.parse(['--unknownOption'], { from: 'user' });
+  }).toThrow();
+  expect(outputError).toHaveBeenCalledWith("error: unknown option '--unknownOption'\n", writeErr);
+});

From bab81d04f22524bc882191ff67e98e8d033521d0 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Tue, 10 Nov 2020 22:39:48 +1300
Subject: [PATCH 17/23] Add JSDoc

---
 index.js | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/index.js b/index.js
index 4a229d18f..f773fc3b7 100644
--- a/index.js
+++ b/index.js
@@ -675,7 +675,18 @@ class Command extends EventEmitter {
   }
 
   /**
-   * WIP
+   * The default output goes to stdout and stderr. You can customise this for special
+   * applications. You can also customise the display of errors by overriding outputError.
+   *
+   * The function signatures are:
+   *
+   *    writeOut(str)
+   *    writeErr(str)
+   *    // columns is used for wrapping the help
+   *    getOutColumns()
+   *    getErrColumns()
+   *    // routines for what is being written out
+   *    outputError(str, write) // used for displaying errors, and not used for displaying help
    *
    * @param {Object} [configuration] - configuration options
    * @return {Command|Object} `this` command for chaining, or stored configuration
@@ -1664,7 +1675,9 @@ Read more on https://git.io/JJc0W`);
   };
 
   /**
-   * WIP
+   * Internal bottleneck for handling of parsing errors.
+   *
+   * @api private
    */
   _displayError(exitCode, code, message) {
     this._outputConfiguration.outputError(`${message}\n`, this._outputConfiguration.writeErr);

From 8a680607c7e7068df904fd4d503ffb7d5cac2c98 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Tue, 10 Nov 2020 23:09:12 +1300
Subject: [PATCH 18/23] Tweak wording

---
 index.js | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/index.js b/index.js
index f773fc3b7..5817acaac 100644
--- a/index.js
+++ b/index.js
@@ -543,15 +543,13 @@ class Command extends EventEmitter {
     this._description = '';
     this._argsDescription = undefined;
 
+    // see .configureOutput() for docs
     this._outputConfiguration = {
-      // Routines for where output is going, stdout or stderr
       writeOut: (str) => process.stdout.write(str),
       writeErr: (str) => process.stderr.write(str),
-      // columns is used for wrapping the help
       getOutColumns: () => process.stdout.isTTY ? process.stdout.columns : undefined,
       getErrColumns: () => process.stderr.isTTY ? process.stderr.columns : undefined,
-      // routines for what is being written out
-      outputError: (str, write) => write(str) // used for displaying errors, and not used for displaying help
+      outputError: (str, write) => write(str)
     };
 
     this._hidden = false;
@@ -678,14 +676,15 @@ class Command extends EventEmitter {
    * The default output goes to stdout and stderr. You can customise this for special
    * applications. You can also customise the display of errors by overriding outputError.
    *
-   * The function signatures are:
+   * The configuration properties are all functions:
    *
+   *    // functions to change where being written, stdout and stderr
    *    writeOut(str)
    *    writeErr(str)
-   *    // columns is used for wrapping the help
+   *    // matching functions to specify columns for wrapping help
    *    getOutColumns()
    *    getErrColumns()
-   *    // routines for what is being written out
+   *    // functions based on what is being written out
    *    outputError(str, write) // used for displaying errors, and not used for displaying help
    *
    * @param {Object} [configuration] - configuration options

From 2a8d1cba58907abbbc5b80bccf015da2ff8be6ba Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Tue, 10 Nov 2020 23:21:10 +1300
Subject: [PATCH 19/23] First cut at TypeScript

---
 typings/index.d.ts | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/typings/index.d.ts b/typings/index.d.ts
index e7ef9f6e8..e921ffbb1 100644
--- a/typings/index.d.ts
+++ b/typings/index.d.ts
@@ -134,6 +134,14 @@ declare namespace commander {
     error: boolean;
     command: Command;
   }
+  interface OutputConfiguration {
+    writeOut?(str: string): void;
+    writeErr?(str: string): void;
+    getOutColumns?(): number;
+    getErrColumns?(): number;
+    outputError?(str: string, write: (str: string) => void): void;
+
+  }
 
   type AddHelpTextPosition = 'beforeAll' | 'before' | 'after' | 'afterAll';
 
@@ -249,6 +257,25 @@ declare namespace commander {
     /** Get configuration */
     configureHelp(): HelpConfiguration;
 
+    /**
+     * The default output goes to stdout and stderr. You can customise this for special
+     * applications. You can also customise the display of errors by overriding outputError.
+     *
+     * The configuration properties are all functions:
+     *
+     *    // functions to change where being written, stdout and stderr
+     *    writeOut(str)
+     *    writeErr(str)
+     *    // matching functions to specify columns for wrapping help
+     *    getOutColumns()
+     *    getErrColumns()
+     *    // functions based on what is being written out
+     *    outputError(str, write) // used for displaying errors, and not used for displaying help
+     */
+    configureOutput(configuration: OutputConfiguration): this;
+    /** Get configuration */
+    configureOutput(): OutputConfiguration;
+
     /**
      * Register callback `fn` for the command.
      *

From 1100c473789a2f5b0f707894cad17b9752a80ba1 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Tue, 10 Nov 2020 23:32:31 +1300
Subject: [PATCH 20/23] Add TypeScript sanity check for configureOutput

---
 typings/commander-tests.ts | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/typings/commander-tests.ts b/typings/commander-tests.ts
index 6854c3e40..d90474179 100644
--- a/typings/commander-tests.ts
+++ b/typings/commander-tests.ts
@@ -263,6 +263,18 @@ const configureHelpThis: commander.Command = program.configureHelp({
 });
 const helpConfiguration: commander.HelpConfiguration = program.configureHelp();
 
+// configureOutput
+const configureOutputThis: commander.Command = program.configureOutput({ });
+const configureOutputConfig: commander.OutputConfiguration = program.configureOutput();
+
+program.configureOutput({
+  writeOut: (str: string) => { },
+  writeErr: (str: string) => { },
+  getOutColumns: () => 80,
+  getErrColumns: () => 80,
+  outputError: (str: string, write: (str: string) => void) => { }
+});
+
 // Help
 const helper = new commander.Help();
 const helperCommand = new commander.Command();

From 7c882f67910ddf052315bd1435237699e96c843a Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Wed, 11 Nov 2020 20:52:41 +1300
Subject: [PATCH 21/23] Add example for configureOutput

---
 examples/configure-output.js | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 examples/configure-output.js

diff --git a/examples/configure-output.js b/examples/configure-output.js
new file mode 100644
index 000000000..207a38f06
--- /dev/null
+++ b/examples/configure-output.js
@@ -0,0 +1,30 @@
+// const commander = require('commander'); // (normal include)
+const commander = require('../'); // include commander in git clone of commander repo
+
+const program = new commander.Command();
+
+function red(str) {
+  return `\x1b[31m${str}\x1b[0m`;
+}
+
+program
+  .configureOutput({
+    // Visibly override write routines for example!
+    writeOut: (str) => process.stdout.write(`[OUT] ${str}`),
+    writeErr: (str) => process.stdout.write(`[ERR] ${str}`),
+    // Output errors in red.
+    outputError: (str, write) => write(red(str))
+  });
+
+program
+  .version('1.2.3')
+  .option('-c, --compress')
+  .command('sub-command');
+
+program.parse();
+
+// Try the following:
+//  node configure-output.js --version
+//  node configure-output.js --unknown
+//  node configure-output.js --help
+//  node configure-output.js

From cc4230979207eac0f676e45c21b628cdcf5f2648 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Sat, 14 Nov 2020 18:04:24 +1300
Subject: [PATCH 22/23] Add configureOutput to README

---
 Readme.md                    | 21 +++++++++++++++++++--
 examples/configure-output.js |  2 +-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/Readme.md b/Readme.md
index c72403c01..c852480ad 100644
--- a/Readme.md
+++ b/Readme.md
@@ -41,7 +41,7 @@ Read this in other languages: English | [简体中文](./Readme_zh-CN.md)
     - [Import into ECMAScript Module](#import-into-ecmascript-module)
     - [Node options such as `--harmony`](#node-options-such-as---harmony)
     - [Debugging stand-alone executable subcommands](#debugging-stand-alone-executable-subcommands)
-    - [Override exit handling](#override-exit-handling)
+    - [Override exit and output handling](#override-exit-and-output-handling)
     - [Additional documentation](#additional-documentation)
   - [Examples](#examples)
   - [Support](#support)
@@ -772,7 +772,7 @@ the inspector port is incremented by 1 for the spawned subcommand.
 
 If you are using VSCode to debug executable subcommands you need to set the `"autoAttachChildProcesses": true` flag in your launch.json configuration.
 
-### Override exit handling
+### Override exit and output handling
 
 By default Commander calls `process.exit` when it detects errors, or after displaying the help or version. You can override
 this behaviour and optionally supply a callback. The default override throws a `CommanderError`.
@@ -790,6 +790,23 @@ try {
 }
 ```
 
+By default Commander is configured for a command-line application and writes to stdout and stderr.
+You can modify this behaviour for custom applications. In addition, you can modify the display of error messages.
+
+Example file: [configure-output.js](./examples/configure-output.js)
+
+
+```js
+program
+  .configureOutput({
+    // Visibly override write routines as example!
+    writeOut: (str) => process.stdout.write(`[OUT] ${str}`),
+    writeErr: (str) => process.stdout.write(`[ERR] ${str}`),
+    // Output errors in red.
+    outputError: (str, write) => write(red(str))
+  });
+```
+
 ### Additional documentation
 
 There is more information available about:
diff --git a/examples/configure-output.js b/examples/configure-output.js
index 207a38f06..f3145a4d2 100644
--- a/examples/configure-output.js
+++ b/examples/configure-output.js
@@ -9,7 +9,7 @@ function red(str) {
 
 program
   .configureOutput({
-    // Visibly override write routines for example!
+    // Visibly override write routines as example!
     writeOut: (str) => process.stdout.write(`[OUT] ${str}`),
     writeErr: (str) => process.stdout.write(`[ERR] ${str}`),
     // Output errors in red.

From 0ae16fba632bd1fc3d47e35e1a0fd6fd0771c067 Mon Sep 17 00:00:00 2001
From: John Gee <john@ruru.gen.nz>
Date: Mon, 16 Nov 2020 21:01:03 +1300
Subject: [PATCH 23/23] Make example in README a little clearer

---
 Readme.md                    | 9 +++++++--
 examples/configure-output.js | 5 +++--
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/Readme.md b/Readme.md
index c852480ad..4c5f5ea8f 100644
--- a/Readme.md
+++ b/Readme.md
@@ -797,13 +797,18 @@ Example file: [configure-output.js](./examples/configure-output.js)
 
 
 ```js
+function errorColor(str) {
+  // Add ANSI escape codes to display text in red.
+  return `\x1b[31m${str}\x1b[0m`;
+}
+
 program
   .configureOutput({
     // Visibly override write routines as example!
     writeOut: (str) => process.stdout.write(`[OUT] ${str}`),
     writeErr: (str) => process.stdout.write(`[ERR] ${str}`),
-    // Output errors in red.
-    outputError: (str, write) => write(red(str))
+    // Highlight errors in color.
+    outputError: (str, write) => write(errorColor(str))
   });
 ```
 
diff --git a/examples/configure-output.js b/examples/configure-output.js
index f3145a4d2..490a322aa 100644
--- a/examples/configure-output.js
+++ b/examples/configure-output.js
@@ -3,7 +3,8 @@ const commander = require('../'); // include commander in git clone of commander
 
 const program = new commander.Command();
 
-function red(str) {
+function errorColor(str) {
+  // Add ANSI escape codes to display text in red.
   return `\x1b[31m${str}\x1b[0m`;
 }
 
@@ -13,7 +14,7 @@ program
     writeOut: (str) => process.stdout.write(`[OUT] ${str}`),
     writeErr: (str) => process.stdout.write(`[ERR] ${str}`),
     // Output errors in red.
-    outputError: (str, write) => write(red(str))
+    outputError: (str, write) => write(errorColor(str))
   });
 
 program