feat: override Module#_compile

Hook into the jest module loading mechanisms for the `Module#_compile` functionality provided by Node. Fixes #10069.
jestjs · May 22, 2020 · 24938b2 · 24938b2
1 parent 81712ba
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 - `[jest-config]` Support config files exporting (`async`) `function`s ([#10001](https://github.com/facebook/jest/pull/10001))
 - `[jest-cli, jest-core]` Add `--selectProjects` CLI argument to filter test suites by project name ([#8612](https://github.com/facebook/jest/pull/8612))
+- `[jest-runtime]` Override `Module#_compile` to hook into jest's module loader ([#10072](https://github.com/facebook/jest/pull/10072))
 
 ### Fixes
 

diff --git a/packages/jest-runtime/src/__tests__/runtime_compile_module.test.js b/packages/jest-runtime/src/__tests__/runtime_compile_module.test.js
@@ -0,0 +1,90 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
+'use strict';
+
+import {Module, builtinModules} from 'module';
+import path from 'path';
+import {pathToFileURL} from 'url';
+// eslint-disable-next-line import/default
+import slash from 'slash';
+import * as fs from 'graceful-fs';
+
+let createRuntime;
+
+describe('Runtime requireModule', () => {
+  beforeEach(() => {
+    createRuntime = require('createRuntime');
+  });
+
+  it('overrides `Module#compile`', () =>
+    createRuntime(__filename).then(runtime => {
+      const exports = runtime.requireModule(runtime.__mockRootPath, 'module');
+      expect(exports.Module).not.toBe(Module);
+
+      const mockFilename = name =>
+        path.join(path.dirname(runtime.__mockRootPath), name);
+
+      {
+        const pathRegularModule = mockFilename('RegularModule.js');
+        const source = fs.readFileSync(pathRegularModule, 'utf-8');
+
+        const module = new exports.Module();
+        module._compile(source, pathRegularModule);
+        expect(module).toMatchObject({
+          children: expect.anything(),
+          exports: expect.anything(),
+          filename: null,
+          loaded: false,
+          parent: null,
+          paths: expect.anything(),
+        });
+        // This is undefined in Node 10 and '' in Node 14 by default.
+        expect(module.id).toBeFalsy();
+        expect(Object.keys(module.exports)).toEqual([
+          'filename',
+          'getModuleStateValue',
+          'isRealModule',
+          'jest',
+          'lazyRequire',
+          'object',
+          'parent',
+          'paths',
+          'setModuleStateValue',
+          'module',
+          'loaded',
+          'isLoaded',
+        ]);
+
+        expect(module.exports.getModuleStateValue()).toBe('default');
+
+        module.exports.lazyRequire();
+
+        // The dynamically compiled module should not be added to the registry,
+        // so no side effects should occur.
+        expect(module.exports.getModuleStateValue()).toBe('default');
+      }
+
+      {
+        const module = new exports.Module();
+        module._compile('exports.value = 12;', mockFilename('dynamic.js'));
+        expect(module.exports).toEqual({value: 12});
+      }
+
+      {
+        const module = new exports.Module();
+        let err;
+        try {
+          module._compile('{"value":12}', mockFilename('dynamic.json'));
+        } catch (e) {
+          err = e;
+        }
+        expect(err.name).toBe('SyntaxError');
+      }
+    }));
+});
diff --git a/packages/jest-runtime/src/index.ts b/packages/jest-runtime/src/index.ts
@@ -70,6 +70,7 @@ type InternalModuleOptions = {
   isInternalModule: boolean;
   supportsDynamicImport: boolean;
   supportsStaticESM: boolean;
+  filenameOverride?: string;
 };
 
 const defaultTransformOptions: InternalModuleOptions = {
@@ -355,7 +356,7 @@ class Runtime {
         return core;
       }
 
-      const transformedCode = this.transformFile(modulePath, {
+      const transformedCode = this.transformFile(modulePath, undefined, {
         isInternalModule: false,
         supportsDynamicImport: true,
         supportsStaticESM: true,
@@ -669,7 +670,13 @@ class Runtime {
     } else {
       // Only include the fromPath if a moduleName is given. Else treat as root.
       const fromPath = moduleName ? from : null;
-      this._execModule(localModule, options, moduleRegistry, fromPath);
+      this._execModule(
+        localModule,
+        undefined,
+        options,
+        moduleRegistry,
+        fromPath,
+      );
     }
     localModule.loaded = true;
   }
@@ -950,16 +957,17 @@ class Runtime {
 
   private _execModule(
     localModule: InitialModule,
+    moduleSource: string | undefined,
     options: InternalModuleOptions | undefined,
     moduleRegistry: ModuleRegistry,
     from: Config.Path | null,
-  ) {
+  ): any | undefined {
     // If the environment was disposed, prevent this module from being executed.
     if (!this._environment.global) {
-      return;
+      return undefined;
     }
 
-    const filename = localModule.filename;
+    const filename = options?.filenameOverride ?? localModule.filename;
     const lastExecutingModulePath = this._currentlyExecutingModulePath;
     this._currentlyExecutingModulePath = filename;
     const origCurrExecutingManualMock = this._isCurrentlyExecutingManualMock;
@@ -981,7 +989,7 @@ class Runtime {
       value: this._createRequireImplementation(localModule, options),
     });
 
-    const transformedCode = this.transformFile(filename, options);
+    const transformedCode = this.transformFile(filename, moduleSource, options);
 
     let compiledFunction: ModuleWrapper | null = null;
 
@@ -1022,15 +1030,15 @@ class Runtime {
         'You are trying to `import` a file after the Jest environment has been torn down.',
       );
       process.exitCode = 1;
-      return;
+      return undefined;
     }
 
     const jestObject = this._createJestObjectFor(filename);
 
     this.jestObjectCaches.set(filename, jestObject);
 
     try {
-      compiledFunction.call(
+      return compiledFunction.call(
         localModule.exports,
         localModule as NodeModule, // module object
         localModule.exports, // module exports
@@ -1055,13 +1063,16 @@ class Runtime {
 
     this._isCurrentlyExecutingManualMock = origCurrExecutingManualMock;
     this._currentlyExecutingModulePath = lastExecutingModulePath;
+
+    return undefined;
   }
 
   private transformFile(
     filename: string,
+    moduleSource: string | undefined,
     options?: InternalModuleOptions,
   ): string {
-    const source = this.readFile(filename);
+    const source = moduleSource ?? this.readFile(filename);
 
     if (options?.isInternalModule) {
       return source;
@@ -1155,8 +1166,28 @@ class Runtime {
       });
     };
 
+    const runtime = this;
+
     // should we implement the class ourselves?
-    class Module extends nativeModule.Module {}
+    class Module extends nativeModule.Module {
+      _compile(content: string, filename: string) {
+        if (typeof content !== 'string') {
+          throw new TypeError('Module#_compile must receive string content');
+        }
+
+        if (typeof filename !== 'string') {
+          throw new TypeError('Module#_compile must receive string filename');
+        }
+
+        return runtime._execModule(
+          this,
+          content,
+          {...defaultTransformOptions, filenameOverride: filename},
+          runtime._moduleRegistry,
+          null,
+        );
+      }
+    }
 
     Object.entries(nativeModule.Module).forEach(([key, value]) => {
       // @ts-expect-error
@@ -1307,16 +1338,28 @@ class Runtime {
     from: InitialModule,
     options?: InternalModuleOptions,
   ): NodeRequire {
+    const filenameOverride = options?.filenameOverride;
+
     // TODO: somehow avoid having to type the arguments - they should come from `NodeRequire/LocalModuleRequire.resolve`
     const resolve = (moduleName: string, options: ResolveOptions) =>
-      this._requireResolve(from.filename, moduleName, options);
+      this._requireResolve(
+        filenameOverride ?? from.filename,
+        moduleName,
+        options,
+      );
     resolve.paths = (moduleName: string) =>
-      this._requireResolvePaths(from.filename, moduleName);
+      this._requireResolvePaths(filenameOverride ?? from.filename, moduleName);
 
     const moduleRequire = (options?.isInternalModule
       ? (moduleName: string) =>
-          this.requireInternalModule(from.filename, moduleName)
-      : this.requireModuleOrMock.bind(this, from.filename)) as NodeRequire;
+          this.requireInternalModule(
+            filenameOverride ?? from.filename,
+            moduleName,
+          )
+      : this.requireModuleOrMock.bind(
+          this,
+          filenameOverride ?? from.filename,
+        )) as NodeRequire;
     moduleRequire.extensions = Object.create(null);
     moduleRequire.resolve = resolve;
     moduleRequire.cache = (() => {

diff --git a/packages/jest-transform/src/ScriptTransformer.ts b/packages/jest-transform/src/ScriptTransformer.ts
@@ -445,7 +445,8 @@ export default class ScriptTransformer {
     let scriptCacheKey = undefined;
     let instrument = false;
 
-    if (!options.isCoreModule) {
+    // Skip cache for core and dynamically loaded modules.
+    if (!options.isCoreModule && typeof options.filenameOverride !== 'string') {
       instrument =
         options.coverageProvider === 'babel' &&
         shouldInstrument(filename, options, this._config);

diff --git a/packages/jest-transform/src/types.ts b/packages/jest-transform/src/types.ts
@@ -25,6 +25,7 @@ export type Options = ShouldInstrumentOptions &
     isInternalModule: boolean;
     supportsDynamicImport: boolean;
     supportsStaticESM: boolean;
+    filenameOverride?: string;
   }>;
 
 // This is fixed in source-map@0.7.x, but we can't upgrade yet since it's async