FileStore now recreates parent cache folders if a write fails (#370)

Summary:
**Summary**

We were seeing periodic cases of builds failing where a cache write would fail. The cause of this seems to be another process cleaning up the /tmp folder periodically - to reduce the chance of these failures this PR adds some fallback logic where if a filestore write fails it will try to recursively recreate its parent cache paths and try writing again.

**Test plan**

Run the new unit test and see that it passes after the FileStore change is made
Pull Request resolved: #370

Differential Revision: D14434560

Pulled By: cpojer

fbshipit-source-id: ff33591b6eb8fb4943d8ea4c4d08d50a0072c04c

Author: mrsharpoblunto

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

@@ -49,15 +49,29 @@ class FileStore<T> {
   }
 
   set(key: Buffer, value: T): void {
+    const filePath = this._getFilePath(key);
+    try {
+      this._set(filePath, value);
+    } catch (err) {
+      if (err.code === 'ENOENT') {
+        mkdirp.sync(path.dirname(filePath));
+        this._set(filePath, value);
+      } else {
+        throw err;
+      }
+    }
+  }
+
+  _set(filePath: string, value: T): void {
     if (value instanceof Buffer) {
-      const fd = fs.openSync(this._getFilePath(key), 'w');
+      const fd = fs.openSync(filePath, 'w');
 
       fs.writeSync(fd, NULL_BYTE_BUFFER);
       fs.writeSync(fd, value);
 
       fs.closeSync(fd);
     } else {
-      fs.writeFileSync(this._getFilePath(key), JSON.stringify(value));
+      fs.writeFileSync(filePath, JSON.stringify(value));
     }
   }
 

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

@@ -41,6 +41,16 @@ describe('FileStore', () => {
     expect(fileStore.get(cache)).toEqual(null);
   });
 
+  it('writes into cache if folder is missing', () => {
+    const fileStore = new FileStore({root: '/root'});
+    const cache = Buffer.from([0xfa, 0xce, 0xb0, 0x0c]);
+    const data = Buffer.from([0xca, 0xc4, 0xe5]);
+
+    require('rimraf').sync('/root');
+    fileStore.set(cache, data);
+    expect(fileStore.get(cache)).toEqual(data);
+  });
+
   it('reads and writes binary data', () => {
     const fileStore = new FileStore({root: '/root'});
     const cache = Buffer.from([0xfa, 0xce, 0xb0, 0x0c]);

packages/metro-memory-fs/src/index.js

@@ -570,6 +570,23 @@ class MemoryFs {
     dirNode.entries.set(basename, this._makeDir(mode));
   };
 
+  rmdirSync = (dirPath: string | Buffer): void => {
+    dirPath = pathStr(dirPath);
+    const {dirNode, node, basename} = this._resolve(dirPath);
+    if (node == null) {
+      throw makeError('ENOENT', dirPath, 'directory does not exist');
+    } else if (node.type === 'file') {
+      if (this._platform === 'posix') {
+        throw makeError('ENOTDIR', dirPath, 'cannot rm a file');
+      } else {
+        throw makeError('ENOENT', dirPath, 'cannot rm a file');
+      }
+    } else if (node.type === 'directory' && node.entries.size) {
+      throw makeError('ENOTEMPTY', dirPath, 'directory not empty');
+    }
+    dirNode.entries.delete(basename);
+  };
+
   symlinkSync = (
     target: string | Buffer,
     filePath: FilePath,