Allow readonly array as parameter to .aliases(), .parse(), .parseAsyn…

…c() (#1669)

* Make .aliases() param readonly

* Make .parse() and .parseAsync() param readonly in TypeScript

tests/command.alias.test.js

@@ -96,3 +96,29 @@ test('when set alias on executable then can get alias', () => {
     .alias(alias);
   expect(program.commands[0].alias()).toEqual(alias);
 });
+
+describe('aliases parameter is treated as readonly, per TypeScript declaration', () => {
+  test('when aliases called then parameter does not change', () => {
+    // Unlikely this could break, but check the API we are declaring in TypeScript.
+    const original = ['b', 'bld'];
+    const param = original.slice();
+    new commander.Command('build').aliases(param);
+    expect(param).toEqual(original);
+  });
+
+  test('when aliases called and aliases later changed then parameter does not change', () => {
+    const original = ['b', 'bld'];
+    const param = original.slice();
+    const cmd = new commander.Command('build').aliases(param);
+    cmd.alias('BBB');
+    expect(param).toEqual(original);
+  });
+
+  test('when aliases called and parameter later changed then aliases does not change', () => {
+    const original = ['b', 'bld'];
+    const param = original.slice();
+    const cmd = new commander.Command('build').aliases(param);
+    param.length = 0;
+    expect(cmd.aliases()).toEqual(original);
+  });
+});

tests/command.parse.test.js

@@ -96,3 +96,71 @@ test('when parse strings instead of array then throw', () => {
     program.parse('node', 'test');
   }).toThrow();
 });
+
+describe('parse parameter is treated as readonly, per TypeScript declaration', () => {
+  test('when parse called then parameter does not change', () => {
+    const program = new commander.Command();
+    program.option('--debug');
+    const original = ['node', '--debug', 'arg'];
+    const param = original.slice();
+    program.parse(param);
+    expect(param).toEqual(original);
+  });
+
+  test('when parse called and parsed args later changed then parameter does not change', () => {
+    const program = new commander.Command();
+    program.option('--debug');
+    const original = ['node', '--debug', 'arg'];
+    const param = original.slice();
+    program.parse(param);
+    program.args.length = 0;
+    program.rawArgs.length = 0;
+    expect(param).toEqual(original);
+  });
+
+  test('when parse called and param later changed then parsed args do not change', () => {
+    const program = new commander.Command();
+    program.option('--debug');
+    const param = ['node', '--debug', 'arg'];
+    program.parse(param);
+    const oldArgs = program.args.slice();
+    const oldRawArgs = program.rawArgs.slice();
+    param.length = 0;
+    expect(program.args).toEqual(oldArgs);
+    expect(program.rawArgs).toEqual(oldRawArgs);
+  });
+});
+
+describe('parseAsync parameter is treated as readonly, per TypeScript declaration', () => {
+  test('when parse called then parameter does not change', async() => {
+    const program = new commander.Command();
+    program.option('--debug');
+    const original = ['node', '--debug', 'arg'];
+    const param = original.slice();
+    await program.parseAsync(param);
+    expect(param).toEqual(original);
+  });
+
+  test('when parseAsync called and parsed args later changed then parameter does not change', async() => {
+    const program = new commander.Command();
+    program.option('--debug');
+    const original = ['node', '--debug', 'arg'];
+    const param = original.slice();
+    await program.parseAsync(param);
+    program.args.length = 0;
+    program.rawArgs.length = 0;
+    expect(param).toEqual(original);
+  });
+
+  test('when parseAsync called and param later changed then parsed args do not change', async() => {
+    const program = new commander.Command();
+    program.option('--debug');
+    const param = ['node', '--debug', 'arg'];
+    await program.parseAsync(param);
+    const oldArgs = program.args.slice();
+    const oldRawArgs = program.rawArgs.slice();
+    param.length = 0;
+    expect(program.args).toEqual(oldArgs);
+    expect(program.rawArgs).toEqual(oldRawArgs);
+  });
+});

typings/index.d.ts

@@ -626,7 +626,7 @@ export class Command {
    *
    * @returns `this` command for chaining
    */
-  parse(argv?: string[], options?: ParseOptions): this;
+  parse(argv?: readonly string[], options?: ParseOptions): this;
 
   /**
    * Parse `argv`, setting options and invoking commands when defined.
@@ -645,7 +645,7 @@ export class Command {
    *
    * @returns Promise
    */
-  parseAsync(argv?: string[], options?: ParseOptions): Promise<this>;
+  parseAsync(argv?: readonly string[], options?: ParseOptions): Promise<this>;
 
   /**
    * Parse options from `argv` removing known options,
@@ -698,7 +698,7 @@ export class Command {
    *
    * @returns `this` command for chaining
    */
-  aliases(aliases: string[]): this;
+  aliases(aliases: readonly string[]): this;
   /**
    * Get aliases for the command.
    */

typings/index.test-d.ts

@@ -187,13 +187,15 @@ expectType<commander.Command>(program.parse(process.argv));
 expectType<commander.Command>(program.parse(['node', 'script.js'], { from: 'node' }));
 expectType<commander.Command>(program.parse(['node', 'script.js'], { from: 'electron' }));
 expectType<commander.Command>(program.parse(['--option'], { from: 'user' }));
+expectType<commander.Command>(program.parse(['node', 'script.js'] as const));
 
 // parseAsync, same tests as parse
 expectType<Promise<commander.Command>>(program.parseAsync());
 expectType<Promise<commander.Command>>(program.parseAsync(process.argv));
 expectType<Promise<commander.Command>>(program.parseAsync(['node', 'script.js'], { from: 'node' }));
 expectType<Promise<commander.Command>>(program.parseAsync(['node', 'script.js'], { from: 'electron' }));
 expectType<Promise<commander.Command>>(program.parseAsync(['--option'], { from: 'user' }));
+expectType<Promise<commander.Command>>(program.parseAsync(['node', 'script.js'] as const));
 
 // parseOptions (and ParseOptionsResult)
 expectType<{operands: string[]; unknown: string[]}>(program.parseOptions(['node', 'script.js', 'hello']));
@@ -224,6 +226,7 @@ expectType<string>(program.alias());
 
 // aliases
 expectType<commander.Command>(program.aliases(['first-alias', 'second-alias']));
+expectType<commander.Command>(program.aliases(['first-alias', 'second-alias'] as const));
 expectType<string[]>(program.aliases());
 
 // usage