Show defaultValueDescription even if defaultValue is not set

lib/help.js

@@ -302,7 +302,10 @@ class Help {
         `choices: ${option.argChoices.map((choice) => JSON.stringify(choice)).join(', ')}`,
       );
     }
-    if (option.defaultValue !== undefined) {
+    if (
+      option.defaultValue !== undefined ||
+      option.defaultValueDescription !== undefined
+    ) {
       // default for boolean and negated more for programmer than end user,
       // but show true/false for boolean option as may be for hand-rolled env or config processing.
       const showDefault =
@@ -344,7 +347,10 @@ class Help {
         `choices: ${argument.argChoices.map((choice) => JSON.stringify(choice)).join(', ')}`,
       );
     }
-    if (argument.defaultValue !== undefined) {
+    if (
+      argument.defaultValue !== undefined ||
+      argument.defaultValueDescription !== undefined
+    ) {
       extraInfo.push(
         `default: ${argument.defaultValueDescription || JSON.stringify(argument.defaultValue)}`,
       );

tests/help.optionDescription.test.js

@@ -70,6 +70,19 @@ describe('optionDescription', () => {
     );
   });
 
+  test('when option has default value description without default value then return description and custom default description', () => {
+    const description = 'description';
+    const defaultValueDescription = 'custom';
+    const option = new commander.Option('-a <value>', description).default(
+      undefined,
+      defaultValueDescription,
+    );
+    const helper = new commander.Help();
+    expect(helper.optionDescription(option)).toEqual(
+      `description (default: ${defaultValueDescription})`,
+    );
+  });
+
   test('when option has choices then return description and choices', () => {
     const description = 'description';
     const choices = ['one', 'two'];