addCommonOption for options common to subcommands

lib/command.js

@@ -24,6 +24,8 @@ class Command extends EventEmitter {
     this.commands = [];
     /** @type {Option[]} */
     this.options = [];
+    /** @type {Option[]} */
+    this.commonOptions = []; // for subcommands
     this.parent = null;
     this._allowUnknownOption = false;
     this._allowExcessArguments = true;
@@ -107,6 +109,21 @@ class Command extends EventEmitter {
     return this;
   }
 
+  /**
+   * Copy common options from sourceCommand
+   *
+   * (Used internally when adding a command using `.command()`.)
+   *
+   * @param {Command} sourceCommand
+   * @return {Command} `this` command for chaining
+   */
+  copyCommonOptions(sourceCommand) {
+    sourceCommand.commonOptions.forEach((commonOption) => {
+      this.addOption(commonOption);
+    });
+    return this;
+  }
+
   /**
    * Define a command.
    *
@@ -154,6 +171,7 @@ class Command extends EventEmitter {
     this.commands.push(cmd);
     cmd.parent = this;
     cmd.copyInheritedSettings(this);
+    cmd.copyCommonOptions(this);
 
     if (desc) return this;
     return cmd;
@@ -574,6 +592,19 @@ Expecting one of '${allowedValues.join("', '")}'`);
     return this;
   }
 
+  /**
+   * Add a common option for subcommands created using .command().
+   *
+   * (See also .copyCommonOptions() for manual copying.)
+   *
+   * @param {Option} option
+   * @return {Command} `this` command for chaining
+   */
+  addCommonOption(option) {
+    this.commonOptions.push(option);
+    return this;
+  }
+
   /**
    * Internal implementation shared by .option() and .requiredOption()
    *

tests/command.chain.test.js

@@ -58,6 +58,12 @@ describe('Command methods that should return this for chaining', () => {
     expect(result).toBe(program);
   });
 
+  test('when call .addCommonOption() then returns this', () => {
+    const program = new Command();
+    const result = program.addCommonOption(new Option('-e'));
+    expect(result).toBe(program);
+  });
+
   test('when call .option() then returns this', () => {
     const program = new Command();
     const result = program.option('-e');
@@ -203,6 +209,13 @@ describe('Command methods that should return this for chaining', () => {
     expect(result).toBe(cmd);
   });
 
+  test('when call .copyCommonOptions() then returns this', () => {
+    const program = new Command();
+    const cmd = new Command();
+    const result = cmd.copyCommonOptions(program);
+    expect(result).toBe(cmd);
+  });
+
   test('when set .nameFromFilename() then returns this', () => {
     const program = new Command();
     const result = program.nameFromFilename('name');