feat: add support for avoiding the module wrapper

Author: SimenB

CHANGELOG.md

@@ -17,6 +17,7 @@
 - `[jest-diff]` Add `changeColor` and `patchColor` options ([#8911](https://github.com/facebook/jest/pull/8911))
 - `[jest-diff]` Add `trailingSpaceFormatter` option and replace cyan with `commonColor` ([#8927](https://github.com/facebook/jest/pull/8927))
 - `[jest-diff]` Add `firstOrLastEmptyLineReplacement` option and export 3 `diffLines` functions ([#8955](https://github.com/facebook/jest/pull/8955))
+- `[jest-environment]` Support compiling a function, rather than using a module wrapper ([#9252](https://github.com/facebook/jest/pull/9252))
 - `[jest-environment-jsdom]` Add `fakeTimersLolex` ([#8925](https://github.com/facebook/jest/pull/8925))
 - `[jest-environment-node]` Add `fakeTimersLolex` ([#8925](https://github.com/facebook/jest/pull/8925))
 - `[jest-environment-node]` Add `queueMicrotask` ([#9140](https://github.com/facebook/jest/pull/9140))
@@ -26,6 +27,7 @@
 - `[jest-reporters]` Export utils for path formatting ([#9162](https://github.com/facebook/jest/pull/9162))
 - `[jest-runner]` Warn if a worker had to be force exited ([#8206](https://github.com/facebook/jest/pull/8206))
 - `[jest-runtime]` [**BREAKING**] Do not export `ScriptTransformer` - it can be imported from `@jest/transform` instead ([#9256](https://github.com/facebook/jest/pull/9256))
+- `[jest-runtime]` Support compiling a function, rather than using a module wrapper ([#9252](https://github.com/facebook/jest/pull/9252))
 - `[jest-snapshot]` Display change counts in annotation lines ([#8982](https://github.com/facebook/jest/pull/8982))
 - `[jest-snapshot]` [**BREAKING**] Improve report when the matcher has properties ([#9104](https://github.com/facebook/jest/pull/9104))
 - `[jest-snapshot]` Improve colors when snapshots are updatable ([#9132](https://github.com/facebook/jest/pull/9132))

TestUtils.ts

@@ -92,6 +92,7 @@ const DEFAULT_PROJECT_CONFIG: Config.ProjectConfig = {
   moduleNameMapper: [],
   modulePathIgnorePatterns: [],
   modulePaths: [],
+  moduleWrapper: true,
   name: 'test_name',
   prettierPath: 'prettier',
   resetMocks: false,

e2e/__tests__/__snapshots__/showConfig.test.ts.snap

@@ -37,6 +37,7 @@ exports[`--showConfig outputs config info and exits 1`] = `
       ],
       "moduleNameMapper": [],
       "modulePathIgnorePatterns": [],
+      "moduleWrapper": true,
       "name": "[md5 hash]",
       "prettierPath": "prettier",
       "resetMocks": false,

packages/jest-cli/src/cli/args.ts

@@ -392,6 +392,11 @@ export const options = {
     string: true,
     type: 'array',
   },
+  moduleWrapper: {
+    default: true,
+    description: 'Wrap transformed modules',
+    type: 'boolean' as 'boolean',
+  },
   noStackTrace: {
     default: undefined,
     description: 'Disables stack trace in test results output',

packages/jest-config/src/Defaults.ts

@@ -38,6 +38,7 @@ const defaultOptions: Config.DefaultOptions = {
   moduleFileExtensions: ['js', 'json', 'jsx', 'ts', 'tsx', 'node'],
   moduleNameMapper: {},
   modulePathIgnorePatterns: [],
+  moduleWrapper: true,
   noStackTrace: false,
   notify: false,
   notifyMode: 'failure-change',

packages/jest-config/src/ValidConfig.ts

@@ -72,6 +72,7 @@ const initialOptions: Config.InitialOptions = {
   },
   modulePathIgnorePatterns: ['<rootDir>/build/'],
   modulePaths: ['/shared/vendor/modules'],
+  moduleWrapper: false,
   name: 'string',
   noStackTrace: false,
   notify: false,

packages/jest-config/src/index.ts

@@ -184,6 +184,7 @@ const groupOptions = (
     moduleNameMapper: options.moduleNameMapper,
     modulePathIgnorePatterns: options.modulePathIgnorePatterns,
     modulePaths: options.modulePaths,
+    moduleWrapper: options.moduleWrapper,
     name: options.name,
     prettierPath: options.prettierPath,
     resetMocks: options.resetMocks,

packages/jest-config/src/normalize.ts

@@ -852,6 +852,7 @@ export default function normalize(
       case 'logHeapUsage':
       case 'maxConcurrency':
       case 'mapCoverage':
+      case 'moduleWrapper':
       case 'name':
       case 'noStackTrace':
       case 'notify':

packages/jest-core/src/lib/__tests__/__snapshots__/log_debug_messages.test.ts.snap

@@ -30,6 +30,7 @@ exports[`prints the config object 1`] = `
     "moduleNameMapper": [],
     "modulePathIgnorePatterns": [],
     "modulePaths": [],
+    "moduleWrapper": true,
     "name": "test_name",
     "prettierPath": "prettier",
     "resetMocks": false,

packages/jest-environment-jsdom/src/index.ts

@@ -130,6 +130,14 @@ class JSDOMEnvironment implements JestEnvironment {
     }
     return null;
   }
+
+  compileFunction(code: string, params: Array<string>, filename: string) {
+    if (this.dom) {
+      // @ts-ignore
+      return this.dom.compileFunction(code, params, {filename}) as any;
+    }
+    return null;
+  }
 }
 
 export = JSDOMEnvironment;

packages/jest-environment-node/src/index.ts

@@ -5,7 +5,13 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {Context, Script, createContext, runInContext} from 'vm';
+import {
+  Context,
+  Script,
+  compileFunction,
+  createContext,
+  runInContext,
+} from 'vm';
 import {Config, Global} from '@jest/types';
 import {ModuleMocker} from 'jest-mock';
 import {installCommonGlobals} from 'jest-util';
@@ -110,6 +116,22 @@ class NodeEnvironment implements JestEnvironment {
     }
     return null;
   }
+
+  compileFunction(code: string, params: Array<string>, filename: string) {
+    if (!compileFunction) {
+      throw new TypeError(
+        "The version of Node you're using does not support compileFunction, please upgrade",
+      );
+    }
+
+    if (this.context) {
+      return compileFunction(code, params, {
+        filename,
+        parsingContext: this.context,
+      }) as any;
+    }
+    return null;
+  }
 }
 
 export = NodeEnvironment;

packages/jest-environment/src/index.ts

@@ -44,6 +44,11 @@ export declare class JestEnvironment {
   fakeTimersLolex: LolexFakeTimers | null;
   moduleMocker: jestMock.ModuleMocker | null;
   runScript<T = unknown>(script: Script): T | null;
+  compileFunction<T = unknown>(
+    code: string,
+    params: Array<string>,
+    filename: string,
+  ): T | null;
   setup(): Promise<void>;
   teardown(): Promise<void>;
   handleTestEvent?(event: Circus.Event, state: Circus.State): void;

packages/jest-runtime/src/index.ts

@@ -730,20 +730,37 @@ class Runtime {
       }
     }
 
-    const script = this.createScriptFromCode(transformedFile.code, filename);
+    let compiledFunction: ModuleWrapper | null;
 
-    const runScript = this._environment.runScript<RunScriptEvalResult>(script);
+    if (this._config.moduleWrapper) {
+      const script = this.createScriptFromCode(transformedFile.code, filename);
 
-    if (runScript === null) {
+      const runScript = this._environment.runScript<RunScriptEvalResult>(
+        script,
+      );
+
+      if (runScript === null) {
+        compiledFunction = null;
+      } else {
+        compiledFunction = runScript[EVAL_RESULT_VARIABLE];
+      }
+    } else {
+      compiledFunction = this._environment.compileFunction<ModuleWrapper>(
+        transformedFile.code,
+        this.constructInjectedModuleParameters(),
+        filename,
+      );
+    }
+
+    if (compiledFunction === null) {
       this._logFormattedReferenceError(
         'You are trying to `import` a file after the Jest environment has been torn down.',
       );
       process.exitCode = 1;
       return;
     }
 
-    //Wrapper
-    runScript[EVAL_RESULT_VARIABLE].call(
+    compiledFunction.call(
       localModule.exports,
       localModule as NodeModule, // module object
       localModule.exports, // module exports
@@ -1107,7 +1124,19 @@ class Runtime {
   }
 
   private wrapCodeInModuleWrapper(content: string) {
-    const args = [
+    const args = this.constructInjectedModuleParameters();
+
+    return (
+      '({"' +
+      EVAL_RESULT_VARIABLE +
+      `":function(${args.join(',')}){` +
+      content +
+      '\n}});'
+    );
+  }
+
+  private constructInjectedModuleParameters() {
+    return [
       'module',
       'exports',
       'require',
@@ -1117,14 +1146,6 @@ class Runtime {
       'jest',
       ...this._config.extraGlobals,
     ];
-
-    return (
-      '({"' +
-      EVAL_RESULT_VARIABLE +
-      `":function(${args.join(',')}){` +
-      content +
-      '\n}});'
-    );
   }
 }
 

packages/jest-types/src/Config.ts

@@ -49,6 +49,7 @@ export type DefaultOptions = {
   moduleFileExtensions: Array<string>;
   moduleNameMapper: Record<string, string>;
   modulePathIgnorePatterns: Array<string>;
+  moduleWrapper: boolean;
   noStackTrace: boolean;
   notify: boolean;
   notifyMode: NotifyMode;
@@ -143,6 +144,7 @@ export type InitialOptions = Partial<{
   };
   modulePathIgnorePatterns: Array<string>;
   modulePaths: Array<string>;
+  moduleWrapper: boolean;
   name: string;
   noStackTrace: boolean;
   notify: boolean;
@@ -318,6 +320,7 @@ export type ProjectConfig = {
   moduleNameMapper: Array<[string, string]>;
   modulePathIgnorePatterns: Array<string>;
   modulePaths?: Array<string>;
+  moduleWrapper: boolean;
   name: string;
   prettierPath: string;
   resetMocks: boolean;