Implements a mapper option

CHANGELOG.md

@@ -84,6 +84,7 @@
 
 - `[jest-cli]` Add `changedSince` to allowed watch mode configs ([#6955](https://github.com/facebook/jest/pull/6955))
 - `[babel-jest]` Add support for `babel.config.js` added in Babel 7.0.0 ([#6911](https://github.com/facebook/jest/pull/6911))
+- `[jest-resolve]` Add support for an experimental `mapper` option (Watchman crawler only) that adds virtual files to the Haste map ([#6940](https://github.com/facebook/jest/pull/6940))
 
 ### Fixes
 

packages/jest-haste-map/src/crawlers/__tests__/watchman.test.js

@@ -44,6 +44,8 @@ const STRAWBERRY_RELATIVE = path.join(FRUITS_RELATIVE, 'strawberry.js');
 const KIWI_RELATIVE = path.join(FRUITS_RELATIVE, 'kiwi.js');
 const TOMATO_RELATIVE = path.join(FRUITS_RELATIVE, 'tomato.js');
 const MELON_RELATIVE = path.join(VEGETABLES_RELATIVE, 'melon.json');
+const DURIAN_RELATIVE = path.join(VEGETABLES_RELATIVE, 'durian.zip');
+
 const WATCH_PROJECT_MOCK = {
   [FRUITS]: {
     relative_path: 'fruits',
@@ -164,6 +166,53 @@ describe('watchman watch', () => {
       expect(client.end).toBeCalled();
     }));
 
+  test('applies the mapper when needed', () => {
+    mockResponse = {
+      'list-capabilities': {
+        [undefined]: {
+          capabilities: ['field-content.sha1hex'],
+        },
+      },
+      query: {
+        [ROOT_MOCK]: {
+          clock: 'c:fake-clock:1',
+          files: [
+            {
+              exists: true,
+              mtime_ms: {toNumber: () => 33},
+              name: 'vegetables/durian.zip',
+            },
+          ],
+          is_fresh_instance: true,
+          version: '4.5.0',
+        },
+      },
+      'watch-project': WATCH_PROJECT_MOCK,
+    };
+
+    return watchmanCrawl({
+      data: {
+        clocks: new Map(),
+        files: new Map(),
+      },
+      extensions: ['js', 'json', 'zip'],
+      ignore: pearMatcher,
+      mapper: n =>
+        n.endsWith('.zip')
+          ? [path.join(n, 'foo.1.js'), path.join(n, 'foo.2.js')]
+          : null,
+      rootDir: ROOT_MOCK,
+      roots: ROOTS,
+    }).then(data => {
+      expect(data.files).toEqual(
+        createMap({
+          [path.join(DURIAN_RELATIVE, 'foo.1.js')]: ['', 33, 0, [], null],
+          [path.join(DURIAN_RELATIVE, 'foo.2.js')]: ['', 33, 0, [], null],
+        }),
+      );
+    });
+  });
+
   test('updates the file object when the clock is given', () => {
     mockResponse = {
       'list-capabilities': {

packages/jest-haste-map/src/crawlers/node.js

@@ -128,6 +128,10 @@ function findNative(
 module.exports = function nodeCrawl(
   options: CrawlerOptions,
 ): Promise<InternalHasteMap> {
+  if (options.mapper) {
+    throw new Error(`Option 'mapper' isn't supported by the Node crawler`);
+  }
+
   const {
     data,
     extensions,

packages/jest-haste-map/src/crawlers/watchman.js

@@ -175,29 +175,43 @@ module.exports = async function watchmanCrawl(
           typeof fileData.mtime_ms === 'number'
             ? fileData.mtime_ms
             : fileData.mtime_ms.toNumber();
+
         let sha1hex = fileData['content.sha1hex'];
         if (typeof sha1hex !== 'string' || sha1hex.length !== 40) {
           sha1hex = null;
         }
 
         const existingFileData = data.files.get(relativeFilePath);
+        let nextData;
+
         if (existingFileData && existingFileData[H.MTIME] === mtime) {
-          files.set(relativeFilePath, existingFileData);
+          nextData = existingFileData;
         } else if (
           existingFileData &&
           sha1hex &&
           existingFileData[H.SHA1] === sha1hex
         ) {
-          files.set(relativeFilePath, [
-            existingFileData[0],
-            mtime,
-            existingFileData[2],
-            existingFileData[3],
-            existingFileData[4],
-          ]);
+          nextData = [...existingFileData];
+          nextData[1] = mtime;
         } else {
           // See ../constants.js
-          files.set(relativeFilePath, ['', mtime, 0, [], sha1hex]);
+          nextData = ['', mtime, 0, [], sha1hex];
+        }
+
+        const mappings = options.mapper ? options.mapper(filePath) : null;
+
+        if (mappings) {
+          for (const absoluteVirtualFilePath of mappings) {
+            if (!ignore(absoluteVirtualFilePath)) {
+              const relativeVirtualFilePath = fastPath.relative(
+                rootDir,
+                absoluteVirtualFilePath,
+              );
+              files.set(relativeVirtualFilePath, nextData);
+            }
+          }
+        } else {
+          files.set(relativeFilePath, nextData);
         }
       }
     }

packages/jest-haste-map/src/index.js

@@ -33,6 +33,7 @@ import * as fastPath from './lib/fast_path';
 import Worker from 'jest-worker';
 
 import type {Console} from 'console';
+import type {Mapper} from './types';
 import type {Path} from 'types/Config';
 import type {
   HasteMap as HasteMapObject,
@@ -55,6 +56,7 @@ type Options = {
   forceNodeFilesystemAPI?: boolean,
   hasteImplModulePath?: string,
   ignorePattern?: ?HasteRegExp,
+  mapper?: ?Mapper,
   maxWorkers: number,
   mocksPattern?: string,
   name: string,
@@ -77,6 +79,7 @@ type InternalOptions = {
   forceNodeFilesystemAPI: boolean,
   hasteImplModulePath?: string,
   ignorePattern: ?HasteRegExp,
+  mapper?: ?Mapper,
   maxWorkers: number,
   mocksPattern: ?RegExp,
   name: string,
@@ -671,6 +674,7 @@ class HasteMap extends EventEmitter {
           extensions: options.extensions,
           forceNodeFilesystemAPI: options.forceNodeFilesystemAPI,
           ignore,
+          mapper: options.mapper,
           rootDir: options.rootDir,
           roots: options.roots,
         }).catch(e => {

packages/jest-haste-map/src/types.js

@@ -10,6 +10,7 @@
 import type {InternalHasteMap, ModuleMetaData} from 'types/HasteMap';
 
 export type IgnoreMatcher = (item: string) => boolean;
+export type Mapper = (item: string) => ?Array<string>;
 
 export type WorkerMessage = {
   computeDependencies: boolean,
@@ -32,6 +33,7 @@ export type CrawlerOptions = {|
   extensions: Array<string>,
   forceNodeFilesystemAPI: boolean,
   ignore: IgnoreMatcher,
+  mapper?: ?Mapper,
   rootDir: string,
   roots: Array<string>,
 |};