Allow setting the default command separately from the construction

index.js

@@ -1679,6 +1679,17 @@ Read more on https://git.io/JJc0W`);
     this._exit(process.exitCode || 0, 'commander.help', '(outputHelp)');
   };
 
+  /**
+   * Sets the default command for the program.
+   *
+   * @param {string} command The name of the command
+   * @api public
+   */
+  default(name) {
+    this._defaultCommandName = name;
+    return this;
+  }
+
   /**
    * Output help information and exit. Display for error situations.
    *

tests/command.default.test.js

@@ -90,3 +90,38 @@ describe('default added command', () => {
     expect(actionMock).toHaveBeenCalled();
   });
 });
+
+describe('default set command', () => {
+  function makeProgram() {
+    const actionMock = jest.fn();
+    const defaultCmd = new commander.Command('default')
+      .allowUnknownOption()
+      .action(actionMock);
+
+    const program = new commander.Command();
+    program
+      .command('other');
+    program
+      .addCommand(defaultCmd);
+    program.default('default');
+    return { program, actionMock };
+  }
+
+  test('when default subcommand and no command then call default', () => {
+    const { program, actionMock } = makeProgram();
+    program.parse('node test.js'.split(' '));
+    expect(actionMock).toHaveBeenCalled();
+  });
+
+  test('when default subcommand and unrecognised argument then call default', () => {
+    const { program, actionMock } = makeProgram();
+    program.parse('node test.js an-argument'.split(' '));
+    expect(actionMock).toHaveBeenCalled();
+  });
+
+  test('when default subcommand and unrecognised option then call default', () => {
+    const { program, actionMock } = makeProgram();
+    program.parse('node test.js --an-option'.split(' '));
+    expect(actionMock).toHaveBeenCalled();
+  });
+});

typings/index.d.ts

@@ -368,6 +368,11 @@ declare namespace commander {
      */
     help(cb?: (str: string) => string): never;
 
+    /**
+     * Set the default command for a program.
+     */
+    default(name: string): void;
+
     /**
      * Add a listener (callback) for when events occur. (Implemented using EventEmitter.)
      *