fix: ensure demandOption is properly supported

Author: Xunnamius

src/discover.ts

@@ -1029,19 +1029,22 @@ export async function discoverCommands(
                   : { [args[0] as string]: args[1] || /* istanbul ignore next */ {} }
               ) as Record<string, Options>;
 
-              Object.entries(options).forEach(([option, optionConfiguration]) => {
-                if ('demandOption' in optionConfiguration) {
-                  debug_(
-                    `discarded attempted mutation of disabled yargs option configuration key "demandOption" (for the %O option) on %O program`,
-                    option,
-                    descriptor
-                  );
-
-                  delete optionConfiguration.demandOption;
-                }
-              });
+              const optionsShallowClone = Object.fromEntries(
+                Object.entries(options).map(([option, optionConfiguration]) => {
+                  if ('demandOption' in optionConfiguration) {
+                    debug_(
+                      `discarded attempted mutation of disabled yargs option configuration key "demandOption" (for the %O option) on %O program`,
+                      option,
+                      descriptor
+                    );
+                  }
+
+                  const { demandOption: _, ...rest } = optionConfiguration;
+                  return [option, rest];
+                })
+              );
 
-              target.options(options);
+              target.options(optionsShallowClone);
               return proxy;
             };
           }

test/fixtures/one-file-builder-object-literal/index.js

@@ -0,0 +1,18 @@
+// @ts-check
+/// <reference path="../index.d.ts"/>
+
+const { dirname, basename } = require('node:path');
+const name = basename(dirname(__filename));
+
+/**
+ * @type {Type.RootConfig}
+ */
+module.exports = {
+  usage: `usage text for root program ${name}`,
+  builder: {
+    option: { demandOption: true, string: true, choices: ['a', 'b'] }
+  },
+  handler: (argv) => {
+    argv.handled_by = __filename;
+  }
+};

test/unit-index.test.ts

@@ -3590,6 +3590,40 @@ describe('<command module auto-discovery>', () => {
     });
   });
 
+  it('does not pass undefined through argv when using "builder"', async () => {
+    expect.hasAssertions();
+
+    const run = bf_util.makeRunner({
+      commandModulePath: getFixturePath('one-file-builder-object-literal')
+    });
+
+    await withMocks(async ({ errorSpy, getExitCode }) => {
+      await expect(run(['--option', 'a'])).resolves.toContainEntries([
+        ['option', 'a'],
+        ['handled_by', expect.any(String)]
+      ]);
+
+      expect(getExitCode()).toBe(bf.FrameworkExitCode.Ok);
+
+      await expect(run(['--option', 'b'])).resolves.toContainEntries([
+        ['option', 'b'],
+        ['handled_by', expect.any(String)]
+      ]);
+
+      expect(getExitCode()).toBe(bf.FrameworkExitCode.Ok);
+
+      await expect(run()).resolves.toBeUndefined();
+
+      expect(getExitCode()).toBe(bf.FrameworkExitCode.DefaultError);
+
+      expect(errorSpy.mock.calls).toStrictEqual([
+        [expect.any(String)],
+        [],
+        [expect.stringContaining('Missing required argument: option')]
+      ]);
+    });
+  });
+
   it('ensures PreExecutionContext::rootPrograms is PreExecutionContext.commands[0].programs and also referenced by the root command full name', async () => {
     expect.hasAssertions();