proto-loader: include Google well known protos

This commit ensures that the Google well known protos are
available because protobufjs only exposes a subset of them.

packages/proto-loader/src/index.ts

@@ -293,3 +293,20 @@ export function loadSync(filename: string, options?: Options): PackageDefinition
   loadedRoot.resolveAll();
   return createPackageDefinition(root, options!);
 }
+
+// Load Google's well-known proto files that aren't exposed by Protobuf.js.
+{
+  // Protobuf.js exposes: any, duration, empty, field_mask, struct, timestamp,
+  // and wrappers. compiler/plugin is excluded in Protobuf.js and here.
+  const wellKnownProtos = ['api', 'descriptor', 'source_context', 'type'];
+  const sourceDir = path.join(path.dirname(require.resolve('protobufjs')),
+                              'google', 'protobuf');
+
+  for (const proto of wellKnownProtos) {
+    const file = path.join(sourceDir, `${proto}.proto`);
+    const descriptor = Protobuf.loadSync(file).toJSON();
+
+    // @ts-ignore
+    Protobuf.common(proto, descriptor.nested.google.nested);
+  }
+}

packages/proto-loader/test/descriptor_type_test.ts

@@ -67,4 +67,9 @@ describe('Descriptor types', () => {
       done();
     }, (error) => {done(error);});
   });
-});
+
+  it('Can use well known Google protos', () => {
+    // This will throw if the well known protos are not available.
+    proto_loader.loadSync(`${TEST_PROTO_DIR}/well_known.proto`);
+  });
+});

packages/proto-loader/test_protos/well_known.proto

@@ -0,0 +1,21 @@
+// Copyright 2019 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+import "google/protobuf/descriptor.proto";
+
+extend google.protobuf.FieldOptions {
+  bool redact = 52000;
+}