react-native-github: remove old fs mock implementation

Reviewed By: rafeca

Differential Revision: D7652914

fbshipit-source-id: 5494305750e7616b5120169266c519f460ae7e6d

packages/metro-memory-fs/src/__tests__/__snapshots__/index-test.js.snap

@@ -1,5 +1,7 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`posix support readlink throws when trying to read a regular file 1`] = `"EINVAL: \`/foo.txt\`: entity is not a symlink"`;
+
 exports[`posix support throws when finding a symlink loop 1`] = `"ELOOP: \`/foo.txt\`: too many levels of symbolic links"`;
 
 exports[`posix support throws when trying to create symlink over existing file 1`] = `"EEXIST: \`/foo.txt\`: directory or file already exists"`;

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

@@ -494,6 +494,25 @@ describe('posix support', () => {
     });
   });
 
+  describe('readlink', () => {
+    it('reads a symlink target', () => {
+      fs.symlinkSync('foo.txt', '/bar.txt');
+      expect(fs.readlinkSync('/bar.txt')).toBe('foo.txt');
+    });
+
+    it('reads a symlink target as buffer', () => {
+      fs.symlinkSync('foo.txt', '/bar.txt');
+      expect(fs.readlinkSync('/bar.txt', 'buffer')).toEqual(
+        Buffer.from('foo.txt'),
+      );
+    });
+
+    it('throws when trying to read a regular file', () => {
+      fs.writeFileSync('/foo.txt', 'test');
+      expectFsError('EINVAL', () => fs.readlinkSync('/foo.txt'));
+    });
+  });
+
   it('throws when trying to read inexistent file', () => {
     expectFsError('ENOENT', () => fs.readFileSync('/foo.txt'));
   });

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

@@ -50,6 +50,7 @@ type Encoding =
   | 'ascii'
   | 'base64'
   | 'binary'
+  | 'buffer'
   | 'hex'
   | 'latin1'
   | 'ucs2'
@@ -99,6 +100,7 @@ const ASYNC_FUNC_NAMES = [
   'read',
   'readdir',
   'readFile',
+  'readlink',
   'realpath',
   'stat',
   'unlink',
@@ -317,6 +319,34 @@ class MemoryFs {
     return result.toString(encoding);
   };
 
+  readlinkSync = (
+    filePath: string | Buffer,
+    options: ?Encoding | {encoding: ?Encoding},
+  ): string | Buffer => {
+    let encoding;
+    if (typeof options === 'string') {
+      encoding = options;
+    } else if (options != null) {
+      ({encoding} = options);
+    }
+    filePath = pathStr(filePath);
+    const {node} = this._resolve(filePath, {keepFinalSymlink: true});
+    if (node == null) {
+      throw makeError('ENOENT', filePath, 'no such file or directory');
+    }
+    if (node.type !== 'symbolicLink') {
+      throw makeError('EINVAL', filePath, 'entity is not a symlink');
+    }
+    if (encoding == null || encoding === 'utf8') {
+      return node.target;
+    }
+    const buf = Buffer.from(node.target);
+    if (encoding == 'buffer') {
+      return buf;
+    }
+    return buf.toString(encoding);
+  };
+
   realpathSync = (filePath: string | Buffer): string => {
     return this._resolve(pathStr(filePath)).realpath;
   };