[react-packager] Use actual error types

Summary:
@public
Previously, we had to use errors as a property on the result object because there was no way to pass custom props between
the child worker and the parent. This has been fixed in node-worker-farm (D2092153) and now we can use regular errors.
This also adapts the transformer to babel-specific errors. Generic errors, however, should still work and render readable
info.

Additionally, I deprecated, but maintained backwards compatiblity for people in OSS that are using custom transformers.

Test Plan:
1. `./runJestTests.sh`
2. `./runJestTests.sh PackagerIntegration`
3. open the playground app
4. Add a syntax error. Say `1=x` somewhere in the file
5. Reload and see error message 'SyntaxError <filename> description (line:col)'
6. Make sure that the stack trace is clickable and it attempts to open the editor to the location

react-packager/src/JSTransformer/__tests__/Transformer-test.js

@@ -57,25 +57,34 @@ describe('Transformer', function() {
   });
 
   pit('should add file info to parse errors', function() {
+    var message = 'message';
+    var snippet = 'snippet';
+
     require('fs').readFile.mockImpl(function(file, callback) {
       callback(null, 'var x;\nvar answer = 1 = x;');
     });
 
     workers.mockImpl(function(data, callback) {
-      var esprimaError = new Error('Error: Line 2: Invalid left-hand side in assignment');
-      esprimaError.description = 'Invalid left-hand side in assignment';
-      esprimaError.lineNumber = 2;
-      esprimaError.column = 15;
-      callback(null, {error: esprimaError});
+      var babelError = new SyntaxError(message);
+      babelError.type = 'SyntaxError';
+      babelError.description = message;
+      babelError.loc = {
+        line: 2,
+        column: 15,
+      };
+      babelError.codeFrame = snippet;
+      callback(babelError);
     });
 
     return new Transformer(OPTIONS).loadFileAndTransform('foo-file.js')
       .catch(function(error) {
         expect(error.type).toEqual('TransformError');
-        expect(error.snippet).toEqual([
-          'var answer = 1 = x;',
-          '             ^',
-        ].join('\n'));
+        expect(error.message).toBe('SyntaxError ' + message);
+        expect(error.lineNumber).toBe(2);
+        expect(error.column).toBe(15);
+        expect(error.filename).toBe('foo-file.js');
+        expect(error.description).toBe(message);
+        expect(error.snippet).toBe(snippet);
       });
   });
 });

react-packager/src/JSTransformer/index.js

@@ -99,7 +99,12 @@ Transformer.prototype.loadFileAndTransform = function(filePath) {
         }).then(
           function(res) {
             if (res.error) {
-              throw formatError(res.error, filePath, sourceCode);
+              console.warn(
+                'Error property on the result value form the transformer',
+                'module is deprecated and will be removed in future versions.',
+                'Please pass an error object as the first argument to the callback'
+              );
+              throw formatError(res.error, filePath);
             }
 
             return new ModuleTransport({
@@ -110,6 +115,8 @@ Transformer.prototype.loadFileAndTransform = function(filePath) {
             });
           }
         );
+      }).catch(function(err) {
+        throw formatError(err, filePath);
       });
   });
 };
@@ -118,8 +125,8 @@ function TransformError() {}
 util.inherits(TransformError, SyntaxError);
 
 function formatError(err, filename, source) {
-  if (err.lineNumber && err.column) {
-    return formatEsprimaError(err, filename, source);
+  if (err.loc) {
+    return formatBabelError(err, filename, source);
   } else {
     return formatGenericError(err, filename, source);
   }
@@ -136,26 +143,16 @@ function formatGenericError(err, filename) {
   return error;
 }
 
-function formatEsprimaError(err, filename, source) {
-  var stack = err.stack.split('\n');
-  stack.shift();
-
-  var msg = 'TransformError: ' + err.description + ' ' +  filename + ':' +
-    err.lineNumber + ':' + err.column;
-  var sourceLine = source.split('\n')[err.lineNumber - 1];
-  var snippet = sourceLine + '\n' + new Array(err.column - 1).join(' ') + '^';
-
-  stack.unshift(msg);
-
+function formatBabelError(err, filename) {
   var error = new TransformError();
-  error.message = msg;
   error.type = 'TransformError';
-  error.stack = stack.join('\n');
-  error.snippet = snippet;
+  error.message = (err.type || error.type) + ' ' + err.message;
+  error.stack = err.stack;
+  error.snippet = err.codeFrame;
+  error.lineNumber = err.loc.line;
+  error.column = err.loc.column;
   error.filename = filename;
-  error.lineNumber = err.lineNumber;
-  error.column = err.column;
-  error.description = err.description;
+  error.description = err.message;
   return error;
 }