Embed metadata directly into the RPC call (#979)

* Embed metadata directly into the RPC call

* [AUTOMATED]: Prettier Code Styling

* Use ...args

* [AUTOMATED]: Prettier Code Styling

* Minimize diff

* Add the OAuth assertion back in

Author: ryanpbrewster

packages/firestore/src/platform_node/grpc_connection.ts

@@ -48,45 +48,32 @@ type UnaryRpc<Req, Resp> = (
   callback: (err?: grpc.ServiceError, resp?: Resp) => void
 ) => grpc.ClientUnaryCall;
 
-function createHeaders(databaseInfo: DatabaseInfo, token: Token | null): {} {
+function createMetadata(
+  databaseInfo: DatabaseInfo,
+  token: Token | null
+): grpc.Metadata {
   assert(
     token === null || token.type === 'OAuth',
     'If provided, token must be OAuth'
   );
 
-  const channelCredentials = databaseInfo.ssl
-    ? grpc.credentials.createSsl()
-    : grpc.credentials.createInsecure();
-
-  const callCredentials = grpc.credentials.createFromMetadataGenerator(
-    (
-      context: { service_url: string },
-      cb: (error: Error | null, metadata?: grpc.Metadata) => void
-    ) => {
-      const metadata = new grpc.Metadata();
-      if (token) {
-        for (const header in token.authHeaders) {
-          if (token.authHeaders.hasOwnProperty(header)) {
-            metadata.set(header, token.authHeaders[header]);
-          }
-        }
+  const metadata = new grpc.Metadata();
+  if (token) {
+    for (const header in token.authHeaders) {
+      if (token.authHeaders.hasOwnProperty(header)) {
+        metadata.set(header, token.authHeaders[header]);
       }
-      metadata.set('x-goog-api-client', X_GOOG_API_CLIENT_VALUE);
-      // This header is used to improve routing and project isolation by the
-      // backend.
-      metadata.set(
-        'google-cloud-resource-prefix',
-        `projects/${databaseInfo.databaseId.projectId}/` +
-          `databases/${databaseInfo.databaseId.database}`
-      );
-      cb(null, metadata);
     }
+  }
+  metadata.set('x-goog-api-client', X_GOOG_API_CLIENT_VALUE);
+  // This header is used to improve routing and project isolation by the
+  // backend.
+  metadata.set(
+    'google-cloud-resource-prefix',
+    `projects/${databaseInfo.databaseId.projectId}/` +
+      `databases/${databaseInfo.databaseId.database}`
   );
-
-  return grpc.credentials.combineChannelCredentials(
-    channelCredentials,
-    callCredentials
-  );
+  return metadata;
 }
 
 // The type of these stubs is dynamically generated by the GRPC runtime
@@ -122,7 +109,9 @@ export class GrpcConnection implements Connection {
   private ensureActiveStub(token: Token | null): GeneratedGrpcStub {
     if (!this.cachedStub || !this.sameToken(this.cachedStub.token, token)) {
       log.debug(LOG_TAG, 'Creating Firestore stub.');
-      const credentials = createHeaders(this.databaseInfo, token);
+      const credentials = this.databaseInfo.ssl
+        ? grpc.credentials.createSsl()
+        : grpc.credentials.createInsecure();
       this.cachedStub = {
         stub: new this.firestore.Firestore(this.databaseInfo.host, credentials),
         token
@@ -142,7 +131,10 @@ export class GrpcConnection implements Connection {
     const stub = this.ensureActiveStub(token);
     const rpc = stub[rpcMethod];
     assert(rpc != null, 'Unknown RPC: ' + rpcName);
-    return rpc.bind(stub);
+
+    const metadata = createMetadata(this.databaseInfo, token);
+    const f = rpc.bind(stub);
+    return (...args) => f(...args, metadata);
   }
 
   invokeRPC<Req, Resp>(