Implements a mapper option

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### Features
 
 - `[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

@@ -42,6 +42,7 @@ const STRAWBERRY = path.join(FRUITS, 'strawberry.js');
 const KIWI = path.join(FRUITS, 'kiwi.js');
 const TOMATO = path.join(FRUITS, 'tomato.js');
 const MELON = path.join(VEGETABLES, 'melon.json');
+const DURIAN = path.join(VEGETABLES, 'durian.zip');
 const WATCH_PROJECT_MOCK = {
   [FRUITS]: {
     relative_path: 'fruits',
@@ -89,6 +90,11 @@ describe('watchman watch', () => {
               mtime_ms: {toNumber: () => 33},
               name: 'vegetables/melon.json',
             },
+            {
+              exists: true,
+              mtime_ms: {toNumber: () => 33},
+              name: 'vegetables/durian.zip',
+            },
           ],
           is_fresh_instance: true,
           version: '4.5.0',
@@ -157,6 +163,28 @@ describe('watchman watch', () => {
       expect(client.end).toBeCalled();
     }));
 
+  test('applies the mapper when needed', async () =>
+    watchmanCrawl({
+      data: {
+        clocks: Object.create(null),
+        files: Object.create(null),
+      },
+      extensions: ['js', 'json', 'zip'],
+      ignore: pearMatcher,
+      mapper: n =>
+        n.endsWith('.zip')
+          ? [path.join(n, 'foo.1.js'), path.join(n, 'foo.2.js')]
+          : null,
+      roots: ROOTS,
+    }).then(data => {
+      expect(data.files).toEqual(
+        Object.assign({}, mockFiles, {
+          [path.join(DURIAN, 'foo.1.js')]: ['', 33, 0, [], null],
+          [path.join(DURIAN, '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

@@ -127,6 +127,10 @@ function findNative(
 module.exports = function nodeCrawl(
   options: CrawlerOptions,
 ): Promise<InternalHasteMap> {
+  if (options.mapper) {
+    throw new Error(`Option 'mapper' isn't supported on this crawler`);
+  }
+
   const {data, extensions, forceNodeFilesystemAPI, ignore, roots} = options;
 
   return new Promise(resolve => {

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

@@ -169,19 +169,32 @@ module.exports = async function watchmanCrawl(
           typeof fileData.mtime_ms === 'number'
             ? fileData.mtime_ms
             : fileData.mtime_ms.toNumber();
+
         const existingFileData = data.files[name];
+        let nextData;
+
         const isOld = existingFileData && existingFileData[H.MTIME] === mtime;
         if (isOld) {
-          files[name] = existingFileData;
+          nextData = existingFileData;
         } else {
           let sha1hex = fileData['content.sha1hex'];
-
           if (typeof sha1hex !== 'string' || sha1hex.length !== 40) {
             sha1hex = null;
           }
-
           // See ../constants.js
-          files[name] = ['', mtime, 0, [], sha1hex];
+          nextData = ['', mtime, 0, [], sha1hex];
+        }
+
+        const mappings = options.mapper ? options.mapper(name) : null;
+
+        if (mappings) {
+          for (const name of mappings) {
+            if (!ignore(name)) {
+              files[name] = nextData;
+            }
+          }
+        } else {
+          files[name] = nextData;
         }
       }
     }

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,
@@ -31,6 +32,7 @@ export type CrawlerOptions = {|
   extensions: Array<string>,
   forceNodeFilesystemAPI: boolean,
   ignore: IgnoreMatcher,
+  mapper?: ?Mapper,
   roots: Array<string>,
 |};