fix: write snapshots to disk even if FS is mocked

CHANGELOG.md

@@ -104,6 +104,7 @@
 - `[jest-runtime]` Fix `requireActual` on node_modules with mock present ([#7404](https://github.com/facebook/jest/pull/7404))
 - `[jest-resolve]` Fix `isBuiltinModule` to support versions of node without `module.builtinModules` ([#7565](https://github.com/facebook/jest/pull/7565))
 - `[babel-jest]` Set `cwd` to be resilient to it changing during the runtime of the tests ([#7574](https://github.com/facebook/jest/pull/7574))
+- `[jest-snapshot]` Write and read snapshots from disk even if `fs` is mocked ([#7080](https://github.com/facebook/jest/pull/7080))
 
 ### Chore & Maintenance
 

e2e/__tests__/__snapshots__/snapshot-mock-fs.test.js.snap

@@ -0,0 +1,9 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`store snapshot even if fs is mocked 1`] = `
+"Test Suites: 1 passed, 1 total
+Tests:       1 passed, 1 total
+Snapshots:   1 written, 1 total
+Time:        <<REPLACED>>
+Ran all test suites."
+`;

e2e/__tests__/snapshot-mock-fs.test.js

@@ -0,0 +1,40 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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.
+ *
+ * @flow
+ */
+'use strict';
+
+const rimraf = require('rimraf');
+const path = require('path');
+const {extractSummary} = require('../Utils');
+const runJest = require('../runJest');
+
+const DIR = path.resolve(__dirname, '../snapshot-mock-fs');
+const snapshotDir = path.resolve(DIR, '__tests__/__snapshots__');
+const snapshotFile = path.resolve(snapshotDir, 'snapshot.test.js.snap');
+
+beforeEach(() => rimraf.sync(snapshotDir));
+afterAll(() => rimraf.sync(snapshotDir));
+
+test('store snapshot even if fs is mocked', () => {
+  const {json, status, stderr} = runJest.json(DIR, ['--ci=false']);
+
+  expect(status).toBe(0);
+  expect(json.numTotalTests).toBe(1);
+  expect(json.numPassedTests).toBe(1);
+
+  expect(stderr).toMatch('1 snapshot written from 1 test suite.');
+  expect(extractSummary(stderr).summary).toMatchSnapshot();
+
+  // $FlowFixMe dynamic require
+  const content = require(snapshotFile);
+  expect(content['snapshot 1']).toBe(`
+Object {
+  "foo": "bar",
+}
+`);
+});

e2e/snapshot-mock-fs/__tests__/snapshot.test.js

@@ -0,0 +1,19 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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.
+ *
+ * @emails oncall+jsinfra
+ */
+'use strict';
+
+const fs = require('fs');
+
+fs.writeFileSync = jest.fn();
+
+test('snapshot', () => {
+  const thing = {foo: 'bar'};
+
+  expect(thing).toMatchSnapshot();
+});

e2e/snapshot-mock-fs/package.json

@@ -0,0 +1,5 @@
+{
+  "jest": {
+    "testEnvironment": "node"
+  }
+}

packages/jest-util/src/installCommonGlobals.js

@@ -10,6 +10,7 @@
 import type {ConfigGlobals} from 'types/Config';
 import type {Global} from 'types/Global';
 
+import fs from 'fs';
 import createProcessObject from './createProcessObject';
 import deepCyclicCopy from './deepCyclicCopy';
 
@@ -31,6 +32,21 @@ export default function(globalObject: Global, globals: ConfigGlobals) {
       value: globalObject.Date.now.bind(globalObject.Date),
       writable: false,
     },
+    [symbol.for('jest-native-read-file')]: {
+      enumerable: false,
+      value: fs.readFileSync.bind(fs),
+      writable: false,
+    },
+    [symbol.for('jest-native-write-file')]: {
+      enumerable: false,
+      value: fs.writeFileSync.bind(fs),
+      writable: false,
+    },
+    [symbol.for('jest-native-exists-file')]: {
+      enumerable: false,
+      value: fs.existsSync.bind(fs),
+      writable: false,
+    },
     'jest-symbol-do-not-touch': {
       enumerable: false,
       value: symbol,

scripts/babel-plugin-jest-native-globals.js

@@ -20,6 +20,15 @@ module.exports = ({template}) => {
   const nowDeclaration = template(`
     var jestNow = global[Symbol.for('jest-native-now')] || global.Date.now;
   `);
+  const fsReadFileDeclaration = template(`
+    var jestReadFile = global[Symbol.for('jest-native-read-file')] || fs.readFileSync;
+  `);
+  const fsWriteFileDeclaration = template(`
+    var jestWriteFile = global[Symbol.for('jest-native-write-file')] || fs.writeFileSync;
+  `);
+  const fsExistsFileDeclaration = template(`
+    var jestExistsFile = global[Symbol.for('jest-native-exists-file')] || fs.existsSync;
+  `);
 
   return {
     name: 'jest-native-globals',
@@ -57,6 +66,56 @@ module.exports = ({template}) => {
 
           path.parentPath.replaceWithSourceString('jestNow');
         }
+        if (
+          path.node.name === 'fs' &&
+          path.parent.property &&
+          ['readFileSync', 'writeFileSync', 'existsSync'].includes(
+            path.parent.property.name
+          )
+        ) {
+          if (
+            !state.jestInjectedRead &&
+            path.parent.property.name === 'readFileSync'
+          ) {
+            state.jestInjectedRead = true;
+            path
+              .findParent(p => p.isProgram())
+              .unshiftContainer('body', fsReadFileDeclaration());
+            path
+              .findParent(p => p.isProgram())
+              .unshiftContainer('body', symbolDeclaration());
+
+            path.parentPath.replaceWithSourceString('jestReadFile');
+          }
+          if (
+            !state.jestInjectedWrite &&
+            path.parent.property.name === 'writeFileSync'
+          ) {
+            state.jestInjectedWrite = true;
+            path
+              .findParent(p => p.isProgram())
+              .unshiftContainer('body', fsWriteFileDeclaration());
+            path
+              .findParent(p => p.isProgram())
+              .unshiftContainer('body', symbolDeclaration());
+
+            path.parentPath.replaceWithSourceString('jestWriteFile');
+          }
+          if (
+            !state.jestInjectedExists &&
+            path.parent.property.name === 'existsSync'
+          ) {
+            state.jestInjectedExists = true;
+            path
+              .findParent(p => p.isProgram())
+              .unshiftContainer('body', fsExistsFileDeclaration());
+            path
+              .findParent(p => p.isProgram())
+              .unshiftContainer('body', symbolDeclaration());
+
+            path.parentPath.replaceWithSourceString('jestExistsFile');
+          }
+        }
       },
     },
   };