chore: cleanup JestEnvironment types (#7988)

Author: SimenB

CHANGELOG.md

@@ -59,7 +59,7 @@
 - `[jest-circus]`: Migrate to TypeScript ([#7916](https://github.com/facebook/jest/pull/7916))
 - `[jest-phabricator]`: Migrate to TypeScript ([#7965](https://github.com/facebook/jest/pull/7965))
 - `[jest-runner]`: Migrate to TypeScript ([#7968](https://github.com/facebook/jest/pull/7968))
-- `[jest-runtime]`: Migrate to TypeScript ([#7964](https://github.com/facebook/jest/pull/7964))
+- `[jest-runtime]`: Migrate to TypeScript ([#7964](https://github.com/facebook/jest/pull/7964), [#7988](https://github.com/facebook/jest/pull/7988))
 - `[@jest/fake-timers]`: Extract FakeTimers class from `jest-util` into a new separate package ([#7987](https://github.com/facebook/jest/pull/7987))
 
 ### Performance

packages/jest-circus/src/legacy-code-todo-rewrite/jestAdapter.ts

@@ -47,7 +47,8 @@ const jestAdapter = async (
   });
 
   if (config.timers === 'fake') {
-    environment.fakeTimers.useFakeTimers();
+    // during setup, this cannot be null (and it's fine to explode if it is)
+    environment.fakeTimers!.useFakeTimers();
   }
 
   globals.beforeEach(() => {
@@ -63,7 +64,8 @@ const jestAdapter = async (
       runtime.resetAllMocks();
 
       if (config.timers === 'fake') {
-        environment.fakeTimers.useFakeTimers();
+        // during setup, this cannot be null (and it's fine to explode if it is)
+        environment.fakeTimers!.useFakeTimers();
       }
     }
 

packages/jest-environment/src/index.ts

@@ -22,19 +22,15 @@ export type EnvironmentContext = {
 // TODO: type this better: https://nodejs.org/api/modules.html#modules_the_module_wrapper
 type ModuleWrapper = (...args: Array<unknown>) => unknown;
 
-export interface JestEnvironment {
-  new (
-    config: Config.ProjectConfig,
-    context?: EnvironmentContext,
-  ): JestEnvironment;
+export declare class JestEnvironment {
+  constructor(config: Config.ProjectConfig);
+  constructor(config: Config.ProjectConfig, context: EnvironmentContext);
+  global: Global.Global;
+  fakeTimers: FakeTimers<unknown> | null;
+  moduleMocker: ModuleMocker | null;
   runScript(
     script: Script,
   ): {[ScriptTransformer.EVAL_RESULT_VARIABLE]: ModuleWrapper} | null;
-  global: Global.Global;
-  // TODO: This is nullable, and TS doesn't understand we deal with it in `jest-runtime`. Should be fixed
-  fakeTimers: FakeTimers<unknown>;
-  testFilePath: Config.Path;
-  moduleMocker: ModuleMocker;
   setup(): Promise<void>;
   teardown(): Promise<void>;
 }

packages/jest-runner/src/runTest.ts

@@ -96,7 +96,7 @@ async function runTestInternal(
     });
   }
 
-  const TestEnvironment: JestEnvironment = require(testEnvironment);
+  const TestEnvironment: typeof JestEnvironment = require(testEnvironment);
   const testFramework: TestFramework =
     process.env.JEST_CIRCUS === '1'
       ? require('jest-circus/runner') // eslint-disable-line import/no-extraneous-dependencies

packages/jest-runtime/src/cli/index.ts

@@ -80,7 +80,7 @@ export function run(cliArgv?: Config.Argv, cliInfo?: Array<string>) {
     watchman: globalConfig.watchman,
   }) as Promise<Context>)
     .then(hasteMap => {
-      const Environment: JestEnvironment = require(config.testEnvironment);
+      const Environment: typeof JestEnvironment = require(config.testEnvironment);
       const environment = new Environment(config);
       setGlobal(
         environment.global,

packages/jest-runtime/src/index.ts

@@ -125,7 +125,8 @@ class Runtime {
     this._isCurrentlyExecutingManualMock = null;
     this._mockFactories = Object.create(null);
     this._mockRegistry = Object.create(null);
-    this._moduleMocker = this._environment.moduleMocker;
+    // during setup, this cannot be null (and it's fine to explode if it is)
+    this._moduleMocker = this._environment.moduleMocker!;
     this._isolatedModuleRegistry = null;
     this._isolatedMockRegistry = null;
     this._moduleRegistry = Object.create(null);
@@ -170,7 +171,7 @@ class Runtime {
     }
   }
 
-  // TODO: Can this be `static shouldInstrument = shouldInstrument;`?
+  // TODO: Make this `static shouldInstrument = shouldInstrument;` after https://github.com/facebook/jest/issues/7846
   static shouldInstrument(
     filename: Config.Path,
     options: ShouldInstrumentOptions,
@@ -934,11 +935,11 @@ class Runtime {
       return jestObject;
     };
     const useFakeTimers = () => {
-      this._environment.fakeTimers.useFakeTimers();
+      _getFakeTimers().useFakeTimers();
       return jestObject;
     };
     const useRealTimers = () => {
-      this._environment.fakeTimers.useRealTimers();
+      _getFakeTimers().useRealTimers();
       return jestObject;
     };
     const resetModules = () => {
@@ -968,15 +969,16 @@ class Runtime {
       return jestObject;
     };
 
-    const _getFakeTimers = () => {
+    const _getFakeTimers = (): NonNullable<JestEnvironment['fakeTimers']> => {
       if (!this._environment.fakeTimers) {
         this._logFormattedReferenceError(
           'You are trying to access a property or method of the Jest environment after it has been torn down.',
         );
         process.exitCode = 1;
       }
 
-      return this._environment.fakeTimers;
+      // We've logged a user message above, so it doesn't matter if we return `null` here
+      return this._environment.fakeTimers!;
     };
 
     const jestObject: Jest = {
@@ -1024,7 +1026,7 @@ class Runtime {
     return jestObject;
   }
 
-  _logFormattedReferenceError(errorMessage: string) {
+  private _logFormattedReferenceError(errorMessage: string) {
     const originalStack = new ReferenceError(errorMessage)
       .stack!.split('\n')
       // Remove this file from the stack (jest-message-utils will keep one line)