Fix(inquirer): Improve ReturnType of inquirer.prompt (not perfect, but better)

Author: SBoudrias

packages/inquirer/src/index.mts

@@ -15,6 +15,7 @@ import {
   editor,
   Separator,
 } from '@inquirer/prompts';
+import type { Prettify } from '@inquirer/type';
 import { default as PromptsRunner } from './ui/prompt.mjs';
 import type {
   PromptCollection,
@@ -48,23 +49,21 @@ const defaultPrompts: PromptCollection = {
  * Create a new self-contained prompt module.
  */
 export function createPromptModule(opt?: StreamOptions) {
-  function promptModule<T extends Answers = Answers>(
+  function promptModule<T extends Answers>(
     questions:
-      | Question<T>
+      | QuestionArray<T>
       | QuestionAnswerMap<T>
       | QuestionObservable<T>
-      | QuestionArray<T>,
+      | Question<T>,
     answers?: Partial<T>,
-  ): Promise<T> & { ui: PromptsRunner } {
+  ): Promise<Prettify<T>> & { ui: PromptsRunner<T> } {
     const runner = new PromptsRunner<T>(promptModule.prompts, opt);
 
     try {
       return runner.run(questions, answers);
     } catch (error) {
-      const promise = Promise.reject(error);
-      // @ts-expect-error Monkey patch the UI on the promise object so
-      promise.ui = runner;
-      return promise as Promise<never> & { ui: PromptsRunner };
+      const promise = Promise.reject<T>(error);
+      return Object.assign(promise, { ui: runner });
     }
   }
 
@@ -85,7 +84,7 @@ export function createPromptModule(opt?: StreamOptions) {
    * Register the defaults provider prompts
    */
   promptModule.restoreDefaultPrompts = function () {
-    this.prompts = { ...defaultPrompts };
+    promptModule.prompts = { ...defaultPrompts };
   };
 
   promptModule.restoreDefaultPrompts();

packages/inquirer/src/types.mts

@@ -13,43 +13,55 @@ import {
 import type { Prettify } from '@inquirer/type';
 import { Observable } from 'rxjs';
 
-export type Answers = { [key: string]: any };
-
-interface QuestionMap {
-  input: { type: 'input' } & Parameters<typeof input>[0];
-  select: { type: 'select' } & Parameters<typeof select>[0];
-  /** @deprecated Prompt type `list` is renamed to `select` */
-  list: { type: 'list' } & Parameters<typeof select>[0];
-  number: { type: 'number' } & Parameters<typeof number>[0];
-  confirm: { type: 'confirm' } & Parameters<typeof confirm>[0];
-  rawlist: { type: 'rawlist' } & Parameters<typeof rawlist>[0];
-  expand: { type: 'expand' } & Parameters<typeof expand>[0];
-  checkbox: { type: 'checkbox' } & Parameters<typeof checkbox>[0];
-  password: { type: 'password' } & Parameters<typeof password>[0];
-  editor: { type: 'editor' } & Parameters<typeof editor>[0];
-}
+// eslint-disable-next-line @typescript-eslint/ban-types
+type LiteralUnion<T extends F, F = string> = T | (F & {});
+type KeyUnion<T> = LiteralUnion<Extract<keyof T, string>>;
+
+export type Answers = {
+  [key: string]: any;
+};
 
-type whenFunction<T extends Answers = Answers> =
+type whenFunction<T extends Answers> =
   | ((answers: Partial<T>) => boolean | Promise<boolean>)
   | ((this: { async: () => () => void }, answers: Partial<T>) => void);
 
-type InquirerFields<T extends Answers = Answers> = {
-  name: keyof T;
+type InquirerFields<T extends Answers> = {
+  name: KeyUnion<T>;
   when?: boolean | whenFunction<T>;
   askAnswered?: boolean;
 };
 
-export type Question<T extends Answers = Answers> = QuestionMap[keyof QuestionMap] &
-  InquirerFields<T>;
+interface QuestionMap<T extends Answers> {
+  input: Prettify<{ type: 'input' } & Parameters<typeof input>[0] & InquirerFields<T>>;
+  select: Prettify<{ type: 'select' } & Parameters<typeof select>[0] & InquirerFields<T>>;
+  list: Prettify<{ type: 'list' } & Parameters<typeof select>[0] & InquirerFields<T>>;
+  number: Prettify<{ type: 'number' } & Parameters<typeof number>[0] & InquirerFields<T>>;
+  confirm: Prettify<
+    { type: 'confirm' } & Parameters<typeof confirm>[0] & InquirerFields<T>
+  >;
+  rawlist: Prettify<
+    { type: 'rawlist' } & Parameters<typeof rawlist>[0] & InquirerFields<T>
+  >;
+  expand: Prettify<{ type: 'expand' } & Parameters<typeof expand>[0] & InquirerFields<T>>;
+  checkbox: Prettify<
+    { type: 'checkbox' } & Parameters<typeof checkbox>[0] & InquirerFields<T>
+  >;
+  password: Prettify<
+    { type: 'password' } & Parameters<typeof password>[0] & InquirerFields<T>
+  >;
+  editor: Prettify<{ type: 'editor' } & Parameters<typeof editor>[0] & InquirerFields<T>>;
+}
+
+export type Question<T extends Answers> = QuestionMap<T>[keyof QuestionMap<T>];
 
-export type QuestionAnswerMap<T extends Answers = Answers> = Record<
-  keyof T,
-  Omit<Question<T>, 'name'>
+export type QuestionAnswerMap<T extends Answers> = Record<
+  KeyUnion<T>,
+  Prettify<Omit<Question<T>, 'name'>>
 >;
 
-export type QuestionArray<T extends Answers = Answers> = Array<Question<T>>;
+export type QuestionArray<T extends Answers> = Question<T>[];
 
-export type QuestionObservable<T extends Answers = Answers> = Observable<Question<T>>;
+export type QuestionObservable<T extends Answers> = Observable<Question<T>>;
 
 export type StreamOptions = Prettify<
   Parameters<typeof input>[1] & { skipTTYChecks?: boolean }

packages/inquirer/src/ui/prompt.mts

@@ -161,8 +161,8 @@ function setupReadlineOptions(opt: StreamOptions = {}) {
   };
 }
 
-function isQuestionMap<T extends Answers = Answers>(
-  questions: Question<T> | QuestionAnswerMap<T> | QuestionArray<T>,
+function isQuestionMap<T extends Answers>(
+  questions: QuestionArray<T> | QuestionAnswerMap<T> | Question<T>,
 ): questions is QuestionAnswerMap<T> {
   return Object.values(questions).every(
     (maybeQuestion) =>
@@ -185,7 +185,7 @@ function isPromptConstructor(
 /**
  * Base interface class other can inherits from
  */
-export default class PromptsRunner<T extends Answers = Answers> extends Base {
+export default class PromptsRunner<T extends Answers> extends Base {
   prompts: PromptCollection;
   answers: Partial<T> = {};
   process: Observable<any>;
@@ -202,12 +202,12 @@ export default class PromptsRunner<T extends Answers = Answers> extends Base {
 
   run(
     questions:
-      | Question<T>
+      | QuestionArray<T>
       | QuestionAnswerMap<T>
       | QuestionObservable<T>
-      | QuestionArray<T>,
+      | Question<T>,
     answers?: Partial<T>,
-  ): Promise<T> & { ui: PromptsRunner } {
+  ): Promise<T> & { ui: PromptsRunner<T> } {
     // Keep global reference to the answers
     this.answers = typeof answers === 'object' ? { ...answers } : {};
 
@@ -244,11 +244,9 @@ export default class PromptsRunner<T extends Answers = Answers> extends Base {
     ).then(
       () => this.onCompletion(),
       (error) => this.onError(error),
-    );
+    ) as Promise<T>;
 
-    // @ts-expect-error Monkey patch the UI on the promise object so
-    promise.ui = this;
-    return promise as Promise<T> & { ui: PromptsRunner };
+    return Object.assign(promise, { ui: this });
   }
 
   /**
@@ -386,7 +384,7 @@ export default class PromptsRunner<T extends Answers = Answers> extends Base {
           }
           return;
         }),
-      ).pipe(filter((val): val is Question => val != null)),
+      ).pipe(filter((val): val is Question<T> => val != null)),
     );
   }
 }

packages/inquirer/test/inquirer.test.mts

@@ -156,12 +156,10 @@ describe('inquirer.prompt', () => {
   });
 
   it('should take a single prompt and return answer', async () => {
-    const config = {
+    const answers = await inquirer.prompt({
       type: 'stub',
       name: 'q1',
-    };
-
-    const answers = await inquirer.prompt(config);
+    });
     expect(answers).toEqual({ q1: 'bar' });
   });
 
@@ -352,7 +350,7 @@ describe('inquirer.prompt', () => {
     }
     inquirer.registerPrompt('stubSelect', FakeSelect);
 
-    const prompts = [
+    await inquirer.prompt([
       {
         type: 'stub',
         name: 'name1',
@@ -363,19 +361,18 @@ describe('inquirer.prompt', () => {
         type: 'stubSelect',
         name: 'name',
         message: 'message',
-        choices(answers) {
+        choices(answers: { name1: string }) {
           expect(answers.name1).toEqual('bar');
           return stubChoices;
         },
       },
-    ];
-
-    await inquirer.prompt(prompts);
+    ]);
   });
 
   it('should expose the Reactive interface', async () => {
     const spy = vi.fn();
-    const prompts = [
+
+    const promise = inquirer.prompt([
       {
         type: 'stub',
         name: 'name1',
@@ -388,9 +385,7 @@ describe('inquirer.prompt', () => {
         message: 'message',
         answer: 'doe',
       },
-    ];
-
-    const promise = inquirer.prompt(prompts);
+    ]);
     promise.ui.process.subscribe(spy);
 
     await promise;
@@ -616,14 +611,15 @@ describe('inquirer.prompt', () => {
     });
 
     it('should not run prompt if nested answer exists for question', async () => {
-      const answers = await inquirer.prompt(
+      const answers = await inquirer.prompt<{ prefilled: { nested: string } }>(
         [
           {
             type: 'input',
             name: 'prefilled.nested',
             when: throwFunc.bind(undefined, 'when'),
             validate: throwFunc.bind(undefined, 'validate'),
             transformer: throwFunc.bind(undefined, 'transformer'),
+            // @ts-expect-error ignoring this unused field for test purpose
             filter: throwFunc.bind(undefined, 'filter'),
             message: 'message',
             default: 'newValue',
@@ -633,7 +629,7 @@ describe('inquirer.prompt', () => {
           prefilled: { nested: 'prefilled' },
         },
       );
-      expect(answers['prefilled'].nested).toEqual('prefilled');
+      expect(answers.prefilled.nested).toEqual('prefilled');
     });
 
     it('should run prompt if answer exists for question and askAnswered is set', async () => {