Add extraGlobals option

CHANGELOG.md

@@ -13,6 +13,7 @@
 - `[jest-haste-map]` [**BREAKING**] Remove name from hash in `HasteMap.getCacheFilePath` ([#7218](https://github.com/facebook/jest/pull/7218))
 - `[babel-preset-jest]` [**BREAKING**] Export a function instead of an object for Babel 7 compatibility ([#7203](https://github.com/facebook/jest/pull/7203))
 - `[jest-haste-map]` [**BREAKING**] Expose relative paths when getting the file iterator ([#7321](https://github.com/facebook/jest/pull/7321))
+- `[jest-runtime]` Add `extraGlobals` to config to load extra global variables into the execution vm ([#7454](https://github.com/facebook/jest/pull/7454))
 - `[jest-util]` Export `specialChars` containing Unicode characters and ANSI escapes for console output ([#7532](https://github.com/facebook/jest/pull/7532))
 - `[jest-config]` Handle typescript (`ts` and `tsx`) by default ([#7533](https://github.com/facebook/jest/pull/7533))
 - `[jest-validate]` Add support for comments in `package.json` using a `"//"` key ([#7295](https://github.com/facebook/jest/pull/7295))

TestUtils.js

@@ -26,6 +26,7 @@ const DEFAULT_GLOBAL_CONFIG: GlobalConfig = {
   enabledTestsMap: null,
   errorOnDeprecated: false,
   expand: false,
+  extraGlobals: [],
   filter: null,
   findRelatedTests: false,
   forceExit: false,
@@ -77,6 +78,7 @@ const DEFAULT_PROJECT_CONFIG: ProjectConfig = {
   detectOpenHandles: false,
   displayName: undefined,
   errorOnDeprecated: false,
+  extraGlobals: [],
   filter: null,
   forceCoverageMatch: [],
   globals: {},

docs/Configuration.md

@@ -273,6 +273,23 @@ Default: `false`
 
 Make calling deprecated APIs throw helpful error messages. Useful for easing the upgrade process.
 
+### `extraGlobals` [array<string>]
+
+Default: `undefined`
+
+Test files run inside a [vm](https://nodejs.org/api/vm.html), which slows calls to global context properties (e.g. `Math`). With this option you can specify extra properties to be defined inside the vm for faster lookups.
+
+For example, if your tests call `Math` often, you can pass it by setting `extraGlobals`.
+
+```json
+{
+  ...
+  "jest": {
+    "extraGlobals": ["Math"]
+  }
+}
+```
+
 ### `forceCoverageMatch` [array<string>]
 
 Default: `['']`

packages/jest-config/src/ValidConfig.js

@@ -44,6 +44,7 @@ export default ({
   displayName: 'project-name',
   errorOnDeprecated: false,
   expand: false,
+  extraGlobals: [],
   filter: '<rootDir>/filter.js',
   forceCoverageMatch: ['**/*.t.js'],
   forceExit: false,

packages/jest-config/src/index.js

@@ -114,6 +114,7 @@ const groupOptions = (
     enabledTestsMap: options.enabledTestsMap,
     errorOnDeprecated: options.errorOnDeprecated,
     expand: options.expand,
+    extraGlobals: options.extraGlobals,
     filter: options.filter,
     findRelatedTests: options.findRelatedTests,
     forceExit: options.forceExit,
@@ -165,6 +166,7 @@ const groupOptions = (
     detectOpenHandles: options.detectOpenHandles,
     displayName: options.displayName,
     errorOnDeprecated: options.errorOnDeprecated,
+    extraGlobals: options.extraGlobals,
     filter: options.filter,
     forceCoverageMatch: options.forceCoverageMatch,
     globals: options.globals,

packages/jest-config/src/normalize.js

@@ -660,6 +660,7 @@ export default function normalize(options: InitialOptions, argv: Argv) {
       case 'displayName':
       case 'errorOnDeprecated':
       case 'expand':
+      case 'extraGlobals':
       case 'globals':
       case 'findRelatedTests':
       case 'forceCoverageMatch':

packages/jest-runtime/src/__tests__/__snapshots__/script_transformer.test.js.snap

@@ -158,6 +158,11 @@ module.exports = () => {
 }});"
 `;
 
+exports[`ScriptTransformer transforms a file properly 3`] = `
+"({\\"Object.<anonymous>\\":function(module,exports,require,__dirname,__filename,global,jest,Math){module.exports = \\"banana\\";
+}});"
+`;
+
 exports[`ScriptTransformer uses multiple preprocessors 1`] = `
 "({\\"Object.<anonymous>\\":function(module,exports,require,__dirname,__filename,global,jest){
           const TRANSFORMED = {

packages/jest-runtime/src/__tests__/script_transformer.test.js

@@ -232,6 +232,12 @@ describe('ScriptTransformer', () => {
     // If we disable coverage, we get a different result.
     scriptTransformer.transform('/fruits/kiwi.js', {collectCoverage: false});
     expect(vm.Script.mock.calls[1][0]).toEqual(snapshot);
+
+    scriptTransformer.transform('/fruits/banana.js', {
+      // to make sure jest isn't declared twice
+      extraGlobals: ['Math', 'jest'],
+    }).script;
+    expect(vm.Script.mock.calls[3][0]).toMatchSnapshot();
   });
 
   it('does not transform Node core modules', () => {

packages/jest-runtime/src/index.js

@@ -645,13 +645,14 @@ class Runtime {
     Object.defineProperty(localModule, 'require', {
       value: this._createRequireImplementation(localModule, options),
     });
-
+    const extraGlobals = this._config.extraGlobals || [];
     const transformedFile = this._scriptTransformer.transform(
       filename,
       {
         collectCoverage: this._coverageOptions.collectCoverage,
         collectCoverageFrom: this._coverageOptions.collectCoverageFrom,
         collectCoverageOnlyFrom: this._coverageOptions.collectCoverageOnlyFrom,
+        extraGlobals,
         isInternalModule,
       },
       this._cacheFS[filename],
@@ -686,8 +687,7 @@ class Runtime {
     }
 
     const wrapper = runScript[ScriptTransformer.EVAL_RESULT_VARIABLE];
-    wrapper.call(
-      localModule.exports, // module context
+    const moduleArguments = new Set([
       localModule, // module object
       localModule.exports, // module exports
       localModule.require, // require implementation
@@ -699,7 +699,17 @@ class Runtime {
         // $FlowFixMe
         (localModule.require: LocalModuleRequire),
       ), // jest object
-    );
+      ...extraGlobals.map(globalVariable => {
+        if (this._environment.global[globalVariable]) {
+          return this._environment.global[globalVariable];
+        }
+
+        throw new Error(
+          `You have requested '${globalVariable}' as a global variable, but it was not present. Please check your config or your global environment.`,
+        );
+      }),
+    ]);
+    wrapper.call(localModule.exports, ...Array.from(moduleArguments));
 
     this._isCurrentlyExecutingManualMock = origCurrExecutingManualMock;
     this._currentlyExecutingModulePath = lastExecutingModulePath;

packages/jest-runtime/src/script_transformer.js

@@ -36,6 +36,7 @@ export type Options = {|
   collectCoverage: boolean,
   collectCoverageFrom: Array<Glob>,
   collectCoverageOnlyFrom: ?{[key: string]: boolean, __proto__: null},
+  extraGlobals?: Array<string>,
   isCoreModule?: boolean,
   isInternalModule?: boolean,
 |};
@@ -313,18 +314,20 @@ export default class ScriptTransformer {
       (this._shouldTransform(filename) || instrument);
 
     try {
+      const extraGlobals = (options && options.extraGlobals) || [];
+
       if (willTransform) {
         const transformedSource = this.transformSource(
           filename,
           content,
           instrument,
         );
 
-        wrappedCode = wrap(transformedSource.code);
+        wrappedCode = wrap(transformedSource.code, ...extraGlobals);
         sourceMapPath = transformedSource.sourceMapPath;
         mapCoverage = transformedSource.mapCoverage;
       } else {
-        wrappedCode = wrap(content);
+        wrappedCode = wrap(content, ...extraGlobals);
       }
 
       return {
@@ -525,11 +528,25 @@ const calcIgnorePatternRegexp = (config: ProjectConfig): ?RegExp => {
   return new RegExp(config.transformIgnorePatterns.join('|'));
 };
 
-const wrap = content =>
-  '({"' +
-  ScriptTransformer.EVAL_RESULT_VARIABLE +
-  '":function(module,exports,require,__dirname,__filename,global,jest){' +
-  content +
-  '\n}});';
+const wrap = (content, ...extras) => {
+  const globals = new Set([
+    'module',
+    'exports',
+    'require',
+    '__dirname',
+    '__filename',
+    'global',
+    'jest',
+    ...extras,
+  ]);
+
+  return (
+    '({"' +
+    ScriptTransformer.EVAL_RESULT_VARIABLE +
+    `":function(${Array.from(globals).join(',')}){` +
+    content +
+    '\n}});'
+  );
+};
 
 ScriptTransformer.EVAL_RESULT_VARIABLE = 'Object.<anonymous>';

types/Config.js

@@ -111,6 +111,7 @@ export type InitialOptions = {
   detectOpenHandles?: boolean,
   displayName?: string,
   expand?: boolean,
+  extraGlobals?: Array<string>,
   filter?: Path,
   findRelatedTests?: boolean,
   forceCoverageMatch?: Array<Glob>,
@@ -204,6 +205,7 @@ export type GlobalConfig = {|
   detectOpenHandles: boolean,
   enabledTestsMap: ?{[key: string]: {[key: string]: boolean}},
   expand: boolean,
+  extraGlobals: Array<string>,
   filter: ?Path,
   findRelatedTests: boolean,
   forceExit: boolean,
@@ -257,6 +259,7 @@ export type ProjectConfig = {|
   detectOpenHandles: boolean,
   displayName: ?string,
   errorOnDeprecated: boolean,
+  extraGlobals: Array<string>,
   filter: ?Path,
   forceCoverageMatch: Array<Glob>,
   globals: ConfigGlobals,