feat(presets): add typing for presets entry point (#2337)

Author: ahnpnl

.eslintignore

@@ -5,5 +5,6 @@ e2e/__workdir_synlink__/
 e2e/__external-repos__/
 coverage/
 website/src/**/*.js
+presets/index.d.ts
 *.config.js
 .eslintrc.js

e2e/__tests__/module-kinds/helpers.ts

@@ -1,4 +1,3 @@
-// @ts-expect-error testing purpose
 import tsJestPresets from '../../../presets'
 import { PackageSets } from '../../__helpers__/templates'
 import { configureTestCase } from '../../__helpers__/test-case'
@@ -33,7 +32,7 @@ const runTestForOptions = (options: TestOptions, preset: AllPresetType = AllPres
   let tsJestPresetToUse
   switch (preset) {
     case AllPreset.DEFAULT_ESM:
-      tsJestPresetToUse = tsJestPresets.defaultEsm
+      tsJestPresetToUse = tsJestPresets.defaultsESM
       break
     case AllPreset.JS_WITH_TS_ESM:
       tsJestPresetToUse = tsJestPresets.jsWithTsESM
@@ -42,7 +41,7 @@ const runTestForOptions = (options: TestOptions, preset: AllPresetType = AllPres
       tsJestPresetToUse = tsJestPresets.jsWithBabelESM
       break
     default:
-      tsJestPresetToUse = tsJestPresets.default
+      tsJestPresetToUse = tsJestPresets.defaults
   }
   const testCase = configureTestCase('module-kinds',
     {

presets/index.d.ts

@@ -0,0 +1,11 @@
+import type { TsJestPresets } from '../dist/types'
+
+declare const _default: {
+    defaults: TsJestPresets;
+    defaultsESM: TsJestPresets;
+    jsWithTs: TsJestPresets;
+    jsWithTsESM: TsJestPresets;
+    jsWithBabel: TsJestPresets;
+    jsWithBabelESM: TsJestPresets;
+};
+export = _default;

src/cli/helpers/presets.ts

@@ -1,4 +1,4 @@
-import type { TsJestPresets } from '../../presets/create-jest-preset'
+import type { TsJestPresets } from '../../types'
 
 /** @internal */
 export const enum JestPresetNames {

src/presets/create-jest-preset.ts

@@ -1,14 +1,10 @@
 import type { Config } from '@jest/types'
 
+import type { TsJestPresets } from '../types'
 import { rootLogger } from '../utils/logger'
 
 const logger = rootLogger.child({ namespace: 'jest-preset' })
 
-export type TsJestPresets = Pick<
-  Config.InitialOptions,
-  'extensionsToTreatAsEsm' | 'moduleFileExtensions' | 'transform' | 'testMatch'
->
-
 export function createJestPreset(allowJs = false, extraOptions: Config.InitialOptions = {}): TsJestPresets {
   logger.debug({ allowJs }, 'creating jest presets', allowJs ? 'handling' : 'not handling', 'JavaScript files')
 

src/types.ts

@@ -34,6 +34,11 @@ export type BabelJestTransformer = {
  */
 export type BabelConfig = _babel.TransformOptions
 
+export type TsJestPresets = Pick<
+  Config.InitialOptions,
+  'extensionsToTreatAsEsm' | 'moduleFileExtensions' | 'transform' | 'testMatch'
+>
+
 export interface AstTransformer<T = Record<string, unknown>> {
   path: string
   options?: T
@@ -211,9 +216,7 @@ export interface TsCompilerInstance extends CompilerInstance {
   configSet: ConfigSet
   program: _ts.Program | undefined
 }
-/**
- * @internal
- */
+
 export interface AstTransformerDesc<T = Record<string, unknown>> {
   name: string
   version: number

website/docs/getting-started/presets.md

@@ -18,7 +18,8 @@ title: Presets
 
 ### Basic usage
 
-In most cases, simply setting the `preset` key to the desired preset name in your Jest config should be enough to start using TypeScript with Jest (assuming you added `ts-jest` to your `devDependencies` of course):
+In most cases, simply setting the `preset` key to the desired preset name in your Jest config should be enough to start
+using TypeScript with Jest (assuming you added `ts-jest` to your `devDependencies` of course):
 
 ```js
 // jest.config.js
@@ -53,11 +54,11 @@ In this case you'll need to use the JavaScript version of Jest config (comment/u
 ```js
 // jest.config.js
 const { defaults: tsjPreset } = require('ts-jest/presets')
-// const { defaultsESM: tsjPreset } = require('ts-jest/presets');
-// const { jsWithTs: tsjPreset } = require('ts-jest/presets');
-// const { jsWithTsESM: tsjPreset } = require('ts-jest/presets');
-// const { jsWithBabel: tsjPreset } = require('ts-jest/presets');
-// const { jsWithBabelESM: tsjPreset } = require('ts-jest/presets');
+// const { defaultsESM: tsjPreset } = require('ts-jest/presets')
+// const { jsWithTs: tsjPreset } = require('ts-jest/presets')
+// const { jsWithTsESM: tsjPreset } = require('ts-jest/presets')
+// const { jsWithBabel: tsjPreset } = require('ts-jest/presets')
+// const { jsWithBabelESM: tsjPreset } = require('ts-jest/presets')
 
 module.exports = {
   // [...]
@@ -67,3 +68,26 @@ module.exports = {
   },
 }
 ```
+
+Or through TypeScript (if `ts-node` is installed):
+
+```ts
+// jest.config.ts
+import type { InitialOptionsTsJest } from 'ts-jest/dist/types'
+import { defaults as tsjPreset } from 'ts-jest/preset'
+// import { defaultsESM as tsjPreset } from 'ts-jest/preset'
+// import { jsWithTs as tsjPreset } from 'ts-jest/preset'
+// import { jsWithTsESM as tsjPreset } from 'ts-jest/preset'
+// import { jsWithBabel as tsjPreset } from 'ts-jest/preset'
+// import { jsWithBabelESM as tsjPreset } from 'ts-jest/preset'
+
+const config: InitialOptionsTsJest = {
+  // [...]
+  transform: {
+    ...tsjPreset.transform,
+    // [...]
+  },
+}
+
+export default config
+```