Make FileStore fully generic

Reviewed By: rafeca

Differential Revision: D7714699

fbshipit-source-id: 7886f99015a88fe4c92c104627aff995ea3dba42

packages/metro-cache/package.json

@@ -16,5 +16,8 @@
     "metro-core": "0.34.0",
     "mkdirp": "^0.5.1",
     "rimraf": "^2.5.4"
+  },
+  "devDependencies": {
+    "metro-memory-fs": "0.34.0"
   }
 }

packages/metro-cache/src/stores/FileStore.js

@@ -21,9 +21,6 @@ export type Options = {|
   root: string,
 |};
 
-const JOINER_DATA = '\0\0';
-const JOINER_LIST = '\0';
-
 class FileStore {
   _root: string;
 
@@ -34,14 +31,7 @@ class FileStore {
 
   get(key: Buffer): ?TransformedCode {
     try {
-      const data = fs.readFileSync(this._getFilePath(key), 'utf8');
-      const [code, dependencies, map] = data.split(JOINER_DATA);
-
-      return {
-        code,
-        dependencies: dependencies ? dependencies.split(JOINER_LIST) : [],
-        map: JSON.parse(map),
-      };
+      return JSON.parse(fs.readFileSync(this._getFilePath(key), 'utf8'));
     } catch (err) {
       if (err.code === 'ENOENT') {
         return null;
@@ -52,13 +42,7 @@ class FileStore {
   }
 
   set(key: Buffer, value: TransformedCode): void {
-    const data = [
-      value.code,
-      value.dependencies.join(JOINER_LIST),
-      JSON.stringify(value.map),
-    ].join(JOINER_DATA);
-
-    fs.writeFileSync(this._getFilePath(key), data);
+    fs.writeFileSync(this._getFilePath(key), JSON.stringify(value));
   }
 
   clear() {

packages/metro-cache/src/stores/__tests__/FileStore-test.js

@@ -0,0 +1,43 @@
+/**
+ * Copyright (c) 2018-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails oncall+javascript_foundation
+ * @format
+ */
+
+'use strict';
+
+describe('FileStore', () => {
+  let FileStore;
+  let fs;
+
+  beforeEach(() => {
+    jest
+      .resetModules()
+      .resetAllMocks()
+      .useFakeTimers()
+      .mock('fs', () => new (require('metro-memory-fs'))());
+
+    FileStore = require('../FileStore');
+    fs = require('fs');
+    jest.spyOn(fs, 'unlinkSync');
+  });
+
+  it('sets and writes into the cache', () => {
+    const fileStore = new FileStore({root: '/root'});
+    const cache = new Buffer([0xfa, 0xce, 0xb0, 0x0c]);
+
+    fileStore.set(cache, {foo: 42});
+    expect(fileStore.get(cache)).toEqual({foo: 42});
+  });
+
+  it('returns null when reading a non-existing file', () => {
+    const fileStore = new FileStore({root: '/root'});
+    const cache = new Buffer([0xfa, 0xce, 0xb0, 0x0c]);
+
+    expect(fileStore.get(cache)).toEqual(null);
+  });
+});