Fix RN redbox messages for syntax errors by including error messages in payload

packages/metro/package.json

@@ -47,6 +47,7 @@
     "mkdirp": "^0.5.1",
     "request": "^2.79.0",
     "rimraf": "^2.5.4",
+    "serialize-error": "^2.1.0",
     "source-map": "^0.5.6",
     "temp": "0.8.3",
     "throat": "^4.1.0",

packages/metro/src/HmrServer/__tests__/HmrServer-test.js

@@ -42,7 +42,7 @@ describe('HmrServer', () => {
         return deltaBundlerMock;
       },
     };
-    getDeltaTransformerMock.reporterMock = {
+    reporterMock = {
       update: jest.fn(),
     };
 
@@ -127,4 +127,46 @@ describe('HmrServer', () => {
       done();
     }, 30);
   });
+
+  it('should return error messages when there is a transform error', async done => {
+    jest.useRealTimers();
+    const sendMessage = jest.fn();
+
+    await hmrServer.onClientConnect(
+      '/hot?bundleEntry=EntryPoint.js&platform=ios',
+      sendMessage,
+    );
+
+    deltaTransformerMock.getDelta.mockImplementation(async () => {
+      const transformError = new SyntaxError('test syntax error');
+      transformError.type = 'TransformError';
+      transformError.filename = 'EntryPoint.js';
+      transformError.lineNumber = 123;
+      throw transformError;
+    });
+
+    deltaTransformerMock.emit('change');
+
+    setTimeout(function() {
+      expect(JSON.parse(sendMessage.mock.calls[0][0])).toEqual({
+        type: 'update-start',
+      });
+      const sentErrorMessage = JSON.parse(sendMessage.mock.calls[1][0]);
+      expect(sentErrorMessage).toMatchObject({type: 'error'});
+      expect(sentErrorMessage.body).toMatchObject({
+        type: 'TransformError',
+        message: 'test syntax error',
+        errors: [
+          {
+            filename: 'EntryPoint.js',
+            lineNumber: 123,
+          },
+        ],
+      });
+      expect(JSON.parse(sendMessage.mock.calls[2][0])).toEqual({
+        type: 'update-done',
+      });
+      done();
+    }, 30);
+  });
 });

packages/metro/src/Server/__tests__/Server-test.js

@@ -301,6 +301,31 @@ describe('processRequest', () => {
         expect(response.body).toEqual('{"delta": "bundle"}');
       });
     });
+
+    it('should include the error message for transform errors', () => {
+      Serializers.deltaBundle.mockImplementation(async () => {
+        const transformError = new SyntaxError('test syntax error');
+        transformError.type = 'TransformError';
+        transformError.filename = 'testFile.js';
+        transformError.lineNumber = 123;
+        throw transformError;
+      });
+
+      return makeRequest(requestHandler, 'index.delta?platform=ios').then(
+        function(response) {
+          expect(() => JSON.parse(response.body)).not.toThrow();
+          const body = JSON.parse(response.body);
+          expect(body).toMatchObject({
+            type: 'TransformError',
+            message: 'test syntax error',
+          });
+          expect(body.errors).toContainEqual({
+            filename: 'testFile.js',
+            lineNumber: 123,
+          });
+        },
+      );
+    });
   });
 
   describe('/onchange endpoint', () => {

packages/metro/src/lib/__tests__/__snapshots__/getTransformCacheKeyFn-test.js.snap

@@ -1,3 +1,3 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`getTransformCacheKeyFn Should return always the same key for the same params 1`] = `"19a529ca8ec00ec50dbbf2de5278262868c1a04f32be6252a9bc5b8df65171914db10f84"`;
+exports[`getTransformCacheKeyFn Should return always the same key for the same params 1`] = `"19a529ca8ec00ec50dbbf2de5278262868c1a04f22073b63c802f6d42d41280131b93e42"`;

packages/metro/src/lib/formatBundlingError.js

@@ -12,6 +12,8 @@
 
 'use strict';
 
+const serializeError = require('serialize-error');
+
 const {
   UnableToResolveError,
 } = require('../node-haste/DependencyGraph/ModuleResolution');
@@ -67,7 +69,7 @@ function formatBundlingError(
       },
     ];
 
-    return error;
+    return serializeError(error);
   } else {
     return {
       type: 'InternalError',

yarn.lock

@@ -4869,6 +4869,10 @@ send@0.13.2:
     range-parser "~1.0.3"
     statuses "~1.2.1"
 
+serialize-error@^2.1.0:
+  version "2.1.0"
+  resolved "https://registry.yarnpkg.com/serialize-error/-/serialize-error-2.1.0.tgz#50b679d5635cdf84667bdc8e59af4e5b81d5f60a"
+
 serve-favicon@~2.3.0:
   version "2.3.2"
   resolved "https://registry.yarnpkg.com/serve-favicon/-/serve-favicon-2.3.2.tgz#dd419e268de012ab72b319d337f2105013f9381f"