Pass docblock pragmas to TestEnvironment constructor.

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### Features
 
 - `[expect]` Improve report when matcher fails, part 15 ([#8281](https://github.com/facebook/jest/pull/8281))
+- `[jest-runner]` Pass docblock pragmas to TestEnvironment constructor ([#8320](https://github.com/facebook/jest/pull/8320))
 
 ### Fixes
 

docs/Configuration.md

@@ -861,6 +861,8 @@ test('use jsdom in this test file', () => {
 
 You can create your own module that will be used for setting up the test environment. The module must export a class with `setup`, `teardown` and `runScript` methods. You can also pass variables from this module to your test suites by assigning them to `this.global` object – this will make them available in your test suites as global variables.
 
+Any docblock pragmas in test files will be passed to the environment constructor and can be used for per-test configuration. If the pragma does not have a value, it will be present in the object with it's value set to an empty string. If the pragma is not present, it will not be present in the object.
+
 _Note: TestEnvironment is sandboxed. Each test suite will trigger setup/teardown in their own TestEnvironment._
 
 Example:
@@ -870,15 +872,21 @@ Example:
 const NodeEnvironment = require('jest-environment-node');
 
 class CustomEnvironment extends NodeEnvironment {
-  constructor(config, context) {
+  constructor(config, {testPath, docblockPragmas}) {
     super(config, context);
-    this.testPath = context.testPath;
+    this.testPath = testPath;
+    this.docblockPragmas = docblockPragmas;
   }
 
   async setup() {
     await super.setup();
     await someSetupTasks(this.testPath);
     this.global.someGlobalObject = createGlobalObject();
+
+    // Will trigger if docblock contains @my-custom-pragma my-pragma-value
+    if (this.docblockPragmas['my-custom-pragma'] === 'my-pragma-value') {
+      // ...
+    }
   }
 
   async teardown() {

e2e/__tests__/testEnvironment.test.ts

@@ -15,5 +15,5 @@ it('respects testEnvironment docblock', () => {
   const {json: result} = runWithJson('test-environment');
 
   expect(result.success).toBe(true);
-  expect(result.numTotalTests).toBe(2);
+  expect(result.numTotalTests).toBe(3);
 });

e2e/test-environment/DocblockPragmasEnvironment.js

@@ -0,0 +1,14 @@
+// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+
+'use strict';
+
+const JSDOMEnvironment = require('jest-environment-jsdom');
+
+class TestEnvironment extends JSDOMEnvironment {
+  constructor(config, context) {
+    super(config, context);
+    this.global.myCustomPragma = context.docblockPragmas['my-custom-pragma'];
+  }
+}
+
+module.exports = TestEnvironment;

e2e/test-environment/EsmDefaultEnvironment.js

@@ -11,8 +11,8 @@ exports.__esModule = true;
 const NodeEnvironment = require('jest-environment-node');
 
 class Env extends NodeEnvironment {
-  constructor(...args) {
-    super(...args);
+  constructor(config, options) {
+    super(config, options);
     this.global.property = 'value';
   }
 }

e2e/test-environment/__tests__/docblockPragmas.test.js

@@ -0,0 +1,10 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * @jest-environment ./DocblockPragmasEnvironment.js
+ * @my-custom-pragma pragma-value
+ */
+
+test('docblock pragmas', () => {
+  expect(myCustomPragma).toEqual('pragma-value'); // eslint-disable-line no-undef
+});

packages/jest-environment/src/index.ts

@@ -14,17 +14,19 @@ import {JestFakeTimers as FakeTimers} from '@jest/fake-timers';
 type JestMockFn = typeof jestMock.fn;
 type JestMockSpyOn = typeof jestMock.spyOn;
 
-export type EnvironmentContext = {
-  console?: Console;
-  testPath?: Config.Path;
-};
+// In Jest 25, remove `Partial` since it's incorrect. The properties are always
+// passed, or not. The context itself is optional, not properties within it.
+export type EnvironmentContext = Partial<{
+  console: Console;
+  docblockPragmas: {[key: string]: string | Array<string>};
+  testPath: Config.Path;
+}>;
 
 // TODO: type this better: https://nodejs.org/api/modules.html#modules_the_module_wrapper
 type ModuleWrapper = (...args: Array<unknown>) => unknown;
 
 export declare class JestEnvironment {
-  constructor(config: Config.ProjectConfig);
-  constructor(config: Config.ProjectConfig, context: EnvironmentContext);
+  constructor(config: Config.ProjectConfig, context?: EnvironmentContext);
   global: Global.Global;
   fakeTimers: FakeTimers<unknown> | null;
   moduleMocker: ModuleMocker | null;

packages/jest-runner/src/runTest.ts

@@ -85,8 +85,8 @@ async function runTestInternal(
   context?: TestRunnerContext,
 ): Promise<RunTestInternalResult> {
   const testSource = fs.readFileSync(path, 'utf8');
-  const parsedDocblock = docblock.parse(docblock.extract(testSource));
-  const customEnvironment = parsedDocblock['jest-environment'];
+  const docblockPragmas = docblock.parse(docblock.extract(testSource));
+  const customEnvironment = docblockPragmas['jest-environment'];
 
   let testEnvironment = config.testEnvironment;
 
@@ -144,6 +144,7 @@ async function runTestInternal(
 
   const environment = new TestEnvironment(config, {
     console: testConsole,
+    docblockPragmas,
     testPath: path,
   });
   const leakDetector = config.detectLeaks