Allow toString to be used for help menu

index.js

@@ -1392,6 +1392,22 @@ class Command extends EventEmitter {
     return width;
   };
 
+  /**
+   * Convert value to a string for help
+   *
+   * @param {object} value
+   * @return {string}
+   */
+
+  _stringify(value) {
+    // Use the `toString` method for objects that don't use the default
+    if (typeof value === 'object' && Object.getPrototypeOf(value).toString !== Object.prototype.toString) {
+      return value.toString();
+    }
+
+    return JSON.stringify(value);
+  }
+
   /**
    * Return help for options.
    *
@@ -1410,7 +1426,7 @@ class Command extends EventEmitter {
     // Explicit options (including version)
     const help = this.options.map((option) => {
       const fullDesc = option.description +
-        ((!option.negate && option.defaultValue !== undefined) ? ' (default: ' + JSON.stringify(option.defaultValue) + ')' : '');
+        ((!option.negate && option.defaultValue !== undefined) ? ' (default: ' + this._stringify(option.defaultValue) + ')' : '');
       return padOptionDetails(option.flags, fullDesc);
     });
 

tests/command.help.test.js

@@ -130,3 +130,20 @@ test('when both help flags masked then not displayed in helpInformation', () =>
   const helpInformation = program.helpInformation();
   expect(helpInformation).not.toMatch('display help');
 });
+
+test('when default value is object with toString and displays in helpInformation', () => {
+  const program = new commander.Command();
+  program
+    .option('--host <host>', 'select host', new URL('http://example.com/'));
+  const helpInformation = program.helpInformation();
+  expect(helpInformation).toContain('http://example.com/');
+});
+
+test('when default value is object and displays in helpInformation', () => {
+  const program = new commander.Command();
+  program
+    .option('--host <host>', 'select host', { host: 'example.com' });
+  const helpInformation = program.helpInformation();
+  expect(helpInformation).not.toContain('[object Object]');
+  expect(helpInformation).toContain('{"host":"example.com"}');
+});