metro-buck: add e2e testing of command

Reviewed By: davidaurelio

Differential Revision: D6533842

fbshipit-source-id: b641559eb3085bac57ab3a1cc80a3f2f86b7ec92

__mocks__/fs.js

@@ -66,29 +66,7 @@ fs.readdir.mockImplementation((filepath, callback) => {
   return callback(null, Object.keys(node));
 });
 
-fs.readFile.mockImplementation(function(filepath, encoding, callback) {
-  filepath = path.normalize(filepath);
-  callback = asyncCallback(callback);
-  if (arguments.length === 2) {
-    callback = encoding;
-    encoding = null;
-  }
-
-  let node;
-  try {
-    node = getToNode(filepath);
-    if (isDirNode(node)) {
-      callback(new Error('Error readFile a dir: ' + filepath));
-    }
-    if (node == null) {
-      return callback(Error('No such file: ' + filepath));
-    } else {
-      return callback(null, node);
-    }
-  } catch (e) {
-    return callback(e);
-  }
-});
+fs.readFile.mockImplementation(asyncify(fs.readFileSync));
 
 fs.readFileSync.mockImplementation(function(filepath, encoding) {
   filepath = path.normalize(filepath);
@@ -156,7 +134,9 @@ fs.mkdirSync.mockImplementation((dirPath, mode) => {
   if (!isDirNode(node)) {
     throw fsError('ENOTDIR', 'not a directory: ' + parentPath);
   }
-  node[path.basename(dirPath)] = {};
+  if (node[path.basename(dirPath)] == null) {
+    node[path.basename(dirPath)] = {};
+  }
 });
 
 function fsError(code, message) {

__tests__/fs-mock-test.js

@@ -64,6 +64,17 @@ describe('fs mock', () => {
        * comment and run Flow. */
       expect(content).toEqual('foobar');
     });
+
+    it('does not erase directories', () => {
+      fs.mkdirSync('/dir', 0o777);
+      fs.writeFileSync('/dir/test', 'foobar', 'utf8');
+      fs.mkdirSync('/dir', 0o777);
+      const content = fs.readFileSync('/dir/test', 'utf8');
+      /* $FlowFixMe(>=0.56.0 site=react_native_oss) This comment suppresses an
+       * error found when Flow v0.56 was deployed. To see the error delete this
+       * comment and run Flow. */
+      expect(content).toEqual('foobar');
+    });
   });
 
   describe('createWriteStream()', () => {