TreeFS: Symlink-enabled, prefix-tree implementation of FileSystem (#…

…926)

Summary:
Pull Request resolved: #926

Currently, `HasteFS` is the only implementation of the `FileSystem` interface, used by Metro to check for file existence during resolution, and to retrieve metadata (file hashes, etc) during transformation. `HasteFS` is based on a simple, performant `Map` of  real paths to metadata.

This diff introduces `TreeFS`, which is based on an in-memory prefix tree representation, split on path separators, of all watched files.

By using a prefix tree, we can lookup files whose paths segments are directory symlinks or files which are themselves links to other files.

We use `TreeFS` in preference to `HasteFS` when `config.resolver.unstable_enableSymlinks` (default: `false`) is `true`.

Reviewed By: motiz88

Differential Revision: D42552999

fbshipit-source-id: 70318ae89a27b560ab1236b147a51031682d3e1f

packages/metro-file-map/src/__tests__/FileSystem-test.js

@@ -0,0 +1,136 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ * @oncall react_native
+ */
+
+import type {FileMetaData, Path} from '../flow-types';
+let mockPathModule;
+jest.mock('path', () => mockPathModule);
+jest.mock('../lib/fast_path', () => mockPathModule);
+
+describe.each([['win32'], ['posix']])(
+  'FileSystem implementations on %s',
+  platform => {
+    beforeAll(() => {
+      mockPathModule = jest.requireActual<{}>('path')[platform];
+    });
+
+    // Convenience function to write paths with posix separators but convert them
+    // to system separators
+    const p: string => string = filePath =>
+      platform === 'win32'
+        ? filePath.replace(/\//g, '\\').replace(/^\\/, 'C:\\')
+        : filePath;
+
+    describe.each([['TreeFS'], ['HasteFS']])('%s', label => {
+      let FileSystem;
+      let fs;
+
+      beforeAll(() => {
+        jest.resetModules();
+        FileSystem =
+          label === 'HasteFS'
+            ? require('../HasteFS').default
+            : require('../lib/TreeFS').default;
+
+        fs = new FileSystem({
+          rootDir: p('/project'),
+          files: new Map([
+            [p('foo/another.js'), ['', 0, 0, 1, '', '', 0]],
+            [p('../outside/external.js'), ['', 0, 0, 1, '', '', 0]],
+            [p('bar.js'), ['', 234, 0, 1, '', '', 0]],
+          ]),
+        });
+      });
+
+      test('getAllFiles returns all files by absolute path', () => {
+        expect(fs.getAllFiles().sort()).toEqual([
+          p('/outside/external.js'),
+          p('/project/bar.js'),
+          p('/project/foo/another.js'),
+        ]);
+      });
+
+      test.each([
+        p('/outside/external.js'),
+        p('/project/bar.js'),
+        p('/project/foo/another.js'),
+      ])('existence check passes: %s', filePath => {
+        expect(fs.exists(filePath)).toBe(true);
+      });
+
+      test('existence check fails for directories', () => {
+        expect(fs.exists(p('/project/foo'))).toBe(false);
+      });
+
+      test('implements linkStats()', () => {
+        expect(fs.linkStats(p('./bar.js'))).toEqual({
+          fileType: 'f',
+          modifiedTime: 234,
+        });
+      });
+
+      describe('matchFiles', () => {
+        test('matches files against a pattern', async () => {
+          expect(
+            fs.matchFiles(
+              mockPathModule.sep === mockPathModule.win32.sep
+                ? /project\\foo/
+                : /project\/foo/,
+            ),
+          ).toEqual([p('/project/foo/another.js')]);
+        });
+      });
+
+      describe('matchFilesWithContext', () => {
+        test('matches files against context', () => {
+          const fs = new FileSystem({
+            rootDir: p('/root'),
+            files: new Map<Path, FileMetaData>([
+              [p('foo/another.js'), ['', 0, 0, 0, '', '', 0]],
+              [p('bar.js'), ['', 0, 0, 0, '', '', 0]],
+            ]),
+          });
+
+          expect(fs.getAllFiles()).toEqual([
+            p('/root/foo/another.js'),
+            p('/root/bar.js'),
+          ]);
+
+          // Test non-recursive skipping deep paths
+          expect(
+            fs.matchFilesWithContext(p('/root'), {
+              filter: new RegExp(
+                // Test starting with `./` since this is mandatory for parity with Webpack.
+                /^\.\/.*/,
+              ),
+              recursive: false,
+            }),
+          ).toEqual([p('/root/bar.js')]);
+
+          // Test inner directory
+          expect(
+            fs.matchFilesWithContext(p('/root/foo'), {
+              filter: new RegExp(/.*/),
+              recursive: true,
+            }),
+          ).toEqual([p('/root/foo/another.js')]);
+
+          // Test recursive
+          expect(
+            fs.matchFilesWithContext(p('/root'), {
+              filter: new RegExp(/.*/),
+              recursive: true,
+            }),
+          ).toEqual([p('/root/foo/another.js'), p('/root/bar.js')]);
+        });
+      });
+    });
+  },
+);

packages/metro-file-map/src/__tests__/index-test.js

@@ -1663,6 +1663,8 @@ describe('HasteMap', () => {
           fileType: 'l',
           modifiedTime: 46,
         });
+        // getModuleName traverses the symlink, verifying the link is read.
+        expect(fileSystem.getModuleName(filePath)).toEqual('Strawberry');
       },
       {config: {enableSymlinks: true}},
     );

packages/metro-file-map/src/index.js

@@ -47,6 +47,7 @@ import deepCloneRawModuleMap from './lib/deepCloneRawModuleMap';
 import * as fastPath from './lib/fast_path';
 import getPlatformExtension from './lib/getPlatformExtension';
 import normalizePathSep from './lib/normalizePathSep';
+import TreeFS from './lib/TreeFS';
 import HasteModuleMap from './ModuleMap';
 import {Watcher} from './Watcher';
 import {worker} from './worker';
@@ -358,10 +359,13 @@ export default class HasteMap extends EventEmitter {
 
         const rootDir = this._options.rootDir;
         const fileData = initialData.files;
-        const fileSystem = new HasteFS({
+        this._startupPerfLogger?.point('constructFileSystem_start');
+        const FileSystem = this._options.enableSymlinks ? TreeFS : HasteFS;
+        const fileSystem = new FileSystem({
           files: fileData,
           rootDir,
         });
+        this._startupPerfLogger?.point('constructFileSystem_end');
         const {map, mocks, duplicates} = initialData;
         const rawModuleMap: RawModuleMap = {
           duplicates,