chore: Migrate babel-plugin-jest-hoist to Typescript (#7898)

CHANGELOG.md

@@ -41,6 +41,7 @@
 - `[@jest/reporter]`: New package extracted from `jest-cli` ([#7902](https://github.com/facebook/jest/pull/7902))
 - `[jest-snapshot]`: Migrate to TypeScript ([#7899](https://github.com/facebook/jest/pull/7899))
 - `[@jest/transform]`: New package extracted from `jest-runtime` ([#7915](https://github.com/facebook/jest/pull/7915))
+- `[babel-plugin-jest-hoist]`: Migrate to TypeScript ([#7898](https://github.com/facebook/jest/pull/7898))
 
 ### Performance
 

packages/babel-jest/tsconfig.json

@@ -4,6 +4,8 @@
     "rootDir": "src",
     "outDir": "build"
   },
-  // TODO: include `babel-preset-jest` even though we don't care about its types
-  "references": [{"path": "../jest-types"}]
+  // TODO: include `babel-preset-jest` if it's ever in TS even though we don't care about its types
+  "references": [
+    {"path": "../jest-types"}
+  ]
 }

packages/babel-plugin-jest-hoist/package.json

@@ -11,5 +11,12 @@
   },
   "license": "MIT",
   "main": "build/index.js",
+  "types": "build/index.d.ts",
+  "dependencies": {
+    "@types/babel__traverse": "^7.0.6"
+  },
+  "devDependencies": {
+    "@babel/types": "^7.3.3"
+  },
   "gitHead": "b16789230fd45056a7f2fa199bae06c7a1780deb"
 }

packages/babel-plugin-jest-hoist/src/index.ts

@@ -0,0 +1,186 @@
+/**
+ * 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.
+ *
+ */
+
+// Only used for types
+// eslint-disable-next-line
+import {NodePath, Visitor} from '@babel/traverse';
+// eslint-disable-next-line
+import {Identifier} from '@babel/types';
+
+const invariant = (condition: unknown, message: string) => {
+  if (!condition) {
+    throw new Error('babel-plugin-jest-hoist: ' + message);
+  }
+};
+
+// We allow `jest`, `expect`, `require`, all default Node.js globals and all
+// ES2015 built-ins to be used inside of a `jest.mock` factory.
+// We also allow variables prefixed with `mock` as an escape-hatch.
+const WHITELISTED_IDENTIFIERS: Set<string> = new Set([
+  'Array',
+  'ArrayBuffer',
+  'Boolean',
+  'DataView',
+  'Date',
+  'Error',
+  'EvalError',
+  'Float32Array',
+  'Float64Array',
+  'Function',
+  'Generator',
+  'GeneratorFunction',
+  'Infinity',
+  'Int16Array',
+  'Int32Array',
+  'Int8Array',
+  'InternalError',
+  'Intl',
+  'JSON',
+  'Map',
+  'Math',
+  'NaN',
+  'Number',
+  'Object',
+  'Promise',
+  'Proxy',
+  'RangeError',
+  'ReferenceError',
+  'Reflect',
+  'RegExp',
+  'Set',
+  'String',
+  'Symbol',
+  'SyntaxError',
+  'TypeError',
+  'URIError',
+  'Uint16Array',
+  'Uint32Array',
+  'Uint8Array',
+  'Uint8ClampedArray',
+  'WeakMap',
+  'WeakSet',
+  'arguments',
+  'console',
+  'expect',
+  'isNaN',
+  'jest',
+  'parseFloat',
+  'parseInt',
+  'require',
+  'undefined',
+]);
+Object.keys(global).forEach(name => {
+  WHITELISTED_IDENTIFIERS.add(name);
+});
+
+const JEST_GLOBAL = {name: 'jest'};
+// TODO: Should be Visitor<{ids: Set<NodePath<Identifier>>}>, but `ReferencedIdentifier` doesn't exist
+const IDVisitor = {
+  ReferencedIdentifier(path: NodePath<Identifier>) {
+    // @ts-ignore: passed as Visitor State
+    this.ids.add(path);
+  },
+  blacklist: ['TypeAnnotation', 'TSTypeAnnotation', 'TSTypeReference'],
+};
+
+const FUNCTIONS: {
+  [key: string]: (args: Array<NodePath>) => boolean;
+} = Object.create(null);
+
+FUNCTIONS.mock = (args: Array<NodePath>) => {
+  if (args.length === 1) {
+    return args[0].isStringLiteral() || args[0].isLiteral();
+  } else if (args.length === 2 || args.length === 3) {
+    const moduleFactory = args[1];
+    invariant(
+      moduleFactory.isFunction(),
+      'The second argument of `jest.mock` must be an inline function.',
+    );
+
+    const ids: Set<NodePath<Identifier>> = new Set();
+    const parentScope = moduleFactory.parentPath.scope;
+    // @ts-ignore: Same as above: ReferencedIdentifier doesn't exist
+    moduleFactory.traverse(IDVisitor, {ids});
+    for (const id of ids) {
+      const {name} = id.node;
+      let found = false;
+      let scope = id.scope;
+
+      while (scope !== parentScope) {
+        if (scope.bindings[name]) {
+          found = true;
+          break;
+        }
+
+        scope = scope.parent;
+      }
+
+      if (!found) {
+        invariant(
+          (scope.hasGlobal(name) && WHITELISTED_IDENTIFIERS.has(name)) ||
+            /^mock/i.test(name) ||
+            // Allow istanbul's coverage variable to pass.
+            /^(?:__)?cov/.test(name),
+          'The module factory of `jest.mock()` is not allowed to ' +
+            'reference any out-of-scope variables.\n' +
+            'Invalid variable access: ' +
+            name +
+            '\n' +
+            'Whitelisted objects: ' +
+            Array.from(WHITELISTED_IDENTIFIERS).join(', ') +
+            '.\n' +
+            'Note: This is a precaution to guard against uninitialized mock ' +
+            'variables. If it is ensured that the mock is required lazily, ' +
+            'variable names prefixed with `mock` (case insensitive) are permitted.',
+        );
+      }
+    }
+
+    return true;
+  }
+  return false;
+};
+
+FUNCTIONS.unmock = (args: Array<NodePath>) =>
+  args.length === 1 && args[0].isStringLiteral();
+FUNCTIONS.deepUnmock = (args: Array<NodePath>) =>
+  args.length === 1 && args[0].isStringLiteral();
+FUNCTIONS.disableAutomock = FUNCTIONS.enableAutomock = (
+  args: Array<NodePath>,
+) => args.length === 0;
+
+export = () => {
+  const shouldHoistExpression = (expr: NodePath): boolean => {
+    if (!expr.isCallExpression()) {
+      return false;
+    }
+
+    const callee = expr.get('callee');
+    // TODO: avoid type casts - the types can be arrays (is it possible to ignore that without casting?)
+    const object = callee.get('object') as NodePath;
+    const property = callee.get('property') as NodePath;
+    return (
+      property.isIdentifier() &&
+      FUNCTIONS[property.node.name] &&
+      (object.isIdentifier(JEST_GLOBAL) ||
+        (callee.isMemberExpression() && shouldHoistExpression(object))) &&
+      FUNCTIONS[property.node.name](expr.get('arguments'))
+    );
+  };
+
+  const visitor: Visitor = {
+    ExpressionStatement(path) {
+      if (shouldHoistExpression(path.get('expression'))) {
+        // @ts-ignore: private, magical property
+        path.node._blockHoist = Infinity;
+      }
+    },
+  };
+
+  return {visitor};
+};

packages/babel-plugin-jest-hoist/tsconfig.json

@@ -0,0 +1,7 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "build"
+  }
+}