feat(transformers): add path-mapping custom AST transformer (#1927)

Usage detail see https://kulshekhar.github.io/ts-jest/user/config/astTransformers

.eslintrc.js

@@ -41,6 +41,8 @@ module.exports = {
     'getter-return': 'warn',
     'guard-for-in': 'error',
     'id-match': 'error',
+    'jest/valid-title': 'off',
+    'jest/no-conditional-expect': 'off',
     'jsdoc/check-alignment': 'error',
     'jsdoc/check-indentation': 'error',
     'jsdoc/newline-after-description': 'warn',

docs/user/config/astTransformers.md

@@ -50,6 +50,54 @@ module.exports = {
 
 </div></div>
 
+### Public transformers
+
+`ts-jest` is able to expose transformers for public usage to provide the possibility to opt-in/out for users. Currently
+the exposed transformers are:
+
+- `path-mapping` convert alias import/export to relative import/export path base on `paths` in `tsconfig`. 
+This transformer works similar to `moduleNameMapper` in `jest.config.js`. When using this transformer, one might not need
+`moduleNameMapper` anymore.
+
+#### Example of opt-in transformers
+
+<div class="row"><div class="col-md-6" markdown="block">
+
+```js
+// jest.config.js
+module.exports = {
+  // [...]
+  globals: {
+    'ts-jest': {
+      astTransformers: {
+        before: ['ts-jest/dist/transformers/path-mapping'],
+      },
+    }
+  }
+};
+```
+
+</div><div class="col-md-6" markdown="block">
+
+```js
+// OR package.json
+{
+  // [...]
+  "jest": {
+    "globals": {
+      "ts-jest": {
+        astTransformers: {
+          "before": ["ts-jest/dist/transformers/path-mapping"]
+        }
+      }
+    }
+  }
+}
+```
+
+</div></div>
+
+
 ### Writing custom TypeScript AST transformers
 
 To write a custom TypeScript AST transformers, one can take a look at [the one](https://github.com/kulshekhar/ts-jest/tree/master/src/transformers) that `ts-jest` is using.

e2e/__cases__/path-mapping/direct-import.spec.ts

@@ -0,0 +1,7 @@
+import { getWelcomeMessage } from '@share/foo'
+
+test('should return welcome message', () => {
+  const userName = 'github-user'
+
+  expect(getWelcomeMessage(userName)).toEqual(`yolo ${userName}`)
+})

e2e/__cases__/path-mapping/dynamic-import.spec.ts

@@ -0,0 +1,6 @@
+test('should return welcome message', async () => {
+  const userName = 'github-user'
+  const foo = await import('@share/foo')
+
+  expect(foo.getWelcomeMessage(userName)).toEqual(`yolo ${userName}`)
+})

e2e/__cases__/path-mapping/export.spec.ts

@@ -0,0 +1,7 @@
+import { getWelcomeMessage } from '@share/export'
+
+test('should return welcome message', async () => {
+  const userName = ''
+
+  expect(getWelcomeMessage(userName)).toEqual(`yolo ${userName}`)
+})

e2e/__cases__/path-mapping/import-default.spec.ts

@@ -0,0 +1,7 @@
+import foo from '@share/foo'
+
+test('should return welcome message', () => {
+  const userName = 'github-user'
+
+  expect(foo(userName)).toBe(`yolo ${userName}`)
+})

e2e/__cases__/path-mapping/import-legacy.spec.ts

@@ -0,0 +1,7 @@
+import foo = require('@share/foo')
+
+test('should return welcome message', () => {
+  const userName = 'github-user'
+
+  expect(foo.getWelcomeMessage(userName)).toEqual(`yolo ${userName}`)
+})

e2e/__cases__/path-mapping/import-require.spec.ts

@@ -0,0 +1,7 @@
+const foo = require('@share/foo')
+
+test('should return welcome message', () => {
+  const userName = 'github-user'
+
+  expect(foo.getWelcomeMessage(userName)).toEqual(`yolo ${userName}`)
+})

e2e/__cases__/path-mapping/import-star.spec.ts

@@ -0,0 +1,7 @@
+import * as foo from '@share/foo'
+
+test('should return welcome message', () => {
+  const userName = 'github-user'
+
+  expect(foo.getWelcomeMessage(userName)).toEqual(`yolo ${userName}`)
+})

e2e/__cases__/path-mapping/import-type.spec.ts

@@ -0,0 +1,9 @@
+import type { Foo } from '@share/foo'
+
+test('should work', () => {
+  const a: Foo = {
+    bar: 1,
+  }
+
+  expect(a).toBeTruthy()
+})

e2e/__cases__/path-mapping/share/export.ts

@@ -0,0 +1 @@
+export { getWelcomeMessage } from '@share/foo'

e2e/__cases__/path-mapping/share/foo.ts

@@ -0,0 +1,13 @@
+export function getWelcomeMessage(username: string): string {
+  return `yolo ${username}`;
+}
+
+function getMessage(username: string) {
+  return getWelcomeMessage(username)
+}
+
+export interface Foo {
+  bar: number
+}
+
+export default getMessage

e2e/__cases__/path-mapping/tsconfig.json

@@ -0,0 +1,12 @@
+{
+  "compilerOptions": {
+    "target": "es5",
+    "baseUrl": ".",
+    "paths": {
+      "@share/*": ["share/*"]
+    }
+  },
+  "exclude": [
+    "node_modules"
+  ]
+}

e2e/__external-repos__/custom-typings/jest.config.js

@@ -1,4 +1,4 @@
 module.exports = {
   preset: 'ts-jest',
-  testEnvironment: 'node',
+  testEnvironment: 'node'
 }

e2e/__external-repos__/path-mapping/.gitignore

@@ -0,0 +1,2 @@
+.idea
+node_modules

e2e/__external-repos__/path-mapping/README.md

@@ -0,0 +1,9 @@
+# A project to demonstrate how to setup `ts-jest` only to work together with `jest`
+
+## Installation
+Run `yarn` to install dependencies
+
+## Overview about configuration
+The project contains:
+- A `jest.config.js` which contains config for `ts-jest`.
+- A `tsconfig.json` which contains config for `typescript`.

e2e/__external-repos__/path-mapping/foo.spec.ts

@@ -0,0 +1,23 @@
+import { isStoreOwner } from './foo';
+import { getWelcomeMessage } from '@share/get-welcome-message';
+import type { Foo } from '@share/typings'
+
+describe('Test optional chaining', () => {
+  test(`should work`, () => {
+    expect(isStoreOwner({
+      isStoreOwner: false,
+    })).toEqual(false)
+  })
+
+  test(`test export *`, () => {
+    expect(getWelcomeMessage('foo')).toEqual('yolo foo')
+  })
+
+  test(`test import type`, () => {
+    const foo: Foo = {
+      bar: 1,
+    }
+
+    expect(foo).toBeTruthy()
+  })
+});

e2e/__external-repos__/path-mapping/foo.ts

@@ -0,0 +1,5 @@
+interface User {
+  isStoreOwner: boolean
+}
+
+export const isStoreOwner = (user: User) => user?.isStoreOwner;

e2e/__external-repos__/path-mapping/jest.config.js

@@ -0,0 +1,16 @@
+// For a detailed explanation regarding each configuration property, visit:
+// https://jestjs.io/docs/en/configuration.html
+/** @typedef {import('ts-jest')} */
+/** @type {import('@jest/types').Config.InitialOptions} */
+module.exports = {
+  preset: 'ts-jest',
+  globals: {
+    'ts-jest': {
+      astTransformers: {
+        before: [
+          'ts-jest/dist/transformers/path-mapping'
+        ]
+      }
+    }
+  }
+};

e2e/__external-repos__/path-mapping/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "ts-jest-example",
+  "version": "1.0.0",
+  "license": "MIT",
+  "devDependencies": {
+    "@types/jest": "26.x",
+    "jest": "26.x",
+    "ts-jest": "26.x",
+    "typescript": "~4.0.2"
+  },
+  "scripts": {
+    "test": "jest"
+  }
+}

e2e/__external-repos__/path-mapping/src/share/get-welcome-message.spec.ts

@@ -0,0 +1,21 @@
+import { getWelcomeMessage } from './get-welcome-message';
+
+describe(`getWelcomeMessage()`, (): void => {
+  let username: string;
+
+  describe(`when the given username is a simple string`, (): void => {
+    beforeEach(
+      (): void => {
+        username = `C0ZEN`;
+      }
+    );
+
+    it(`should return a message for this username`, (): void => {
+      expect.assertions(1);
+
+      const result = getWelcomeMessage(username);
+
+      expect(result).toStrictEqual(`yolo C0ZEN`);
+    });
+  });
+});

e2e/__external-repos__/path-mapping/src/share/get-welcome-message.ts

@@ -0,0 +1,3 @@
+export function getWelcomeMessage(username: string): string {
+  return `yolo ${username}`;
+}

e2e/__external-repos__/path-mapping/src/share/typings.ts

@@ -0,0 +1,3 @@
+export interface Foo {
+  bar: number
+}

e2e/__external-repos__/path-mapping/tsconfig.json

@@ -0,0 +1,16 @@
+{
+  "compilerOptions": {
+    "target": "es5",
+    "module": "commonjs",
+    "baseUrl": ".",
+    "declaration": true,
+    "strict": true,
+    "forceConsistentCasingInFileNames": true,
+    "paths": {
+      "@share/*": ["src/share/*"]
+    }
+  },
+  "exclude": [
+    "node_modules"
+  ]
+}