fix: return Google Error when there is a missing required parameter

src/fallbackRest.ts

@@ -61,6 +61,10 @@ export function encodeRequest(
     rpc.parsedOptions,
     rpc.resolvedRequestType!.fields
   );
+  if (transcoded instanceof GoogleError) {
+    throw transcoded;
+  }
+
   if (!transcoded) {
     throw new Error(
       `Cannot build HTTP request for ${JSON.stringify(json)}, method: ${

src/fallbackServiceStub.ts

@@ -25,6 +25,7 @@ import {hasWindowFetch, hasAbortController} from './featureDetection';
 import {AuthClient} from './fallback';
 import {StreamArrayParser} from './streamArrayParser';
 import {pipeline, PipelineSource} from 'stream';
+import {GoogleError} from './googleError';
 
 interface NodeFetchType {
   (url: RequestInfo, init?: RequestInit): Promise<Response>;
@@ -37,7 +38,7 @@ export interface FallbackServiceStub {
     options: {},
     metadata: {},
     callback: (err?: Error, response?: {} | undefined) => void
-  ) => StreamArrayParser | {cancel: () => void};
+  ) => StreamArrayParser | {cancel: () => void} | Promise<GoogleError>;
 }
 
 export interface FetchParameters {
@@ -91,14 +92,18 @@ export function generateServiceStub(
         : new NodeAbortController();
       const cancelSignal = cancelController.signal as AbortSignal;
       let cancelRequested = false;
-
-      const fetchParameters = requestEncoder(
-        rpc,
-        protocol,
-        servicePath,
-        servicePort,
-        request
-      );
+      let fetchParameters: FetchParameters;
+      try {
+        fetchParameters = requestEncoder(
+          rpc,
+          protocol,
+          servicePath,
+          servicePort,
+          request
+        );
+      } catch (err) {
+        return Promise.resolve(callback(err));
+      }
       const url = fetchParameters.url;
       const headers = fetchParameters.headers;
       for (const key of Object.keys(options)) {

src/transcoding.ts

@@ -20,6 +20,7 @@
 import {JSONObject, JSONValue} from 'proto3-json-serializer';
 import {Field} from 'protobufjs';
 import {google} from '../protos/http';
+import {GoogleError} from './googleError';
 import {camelToSnakeCase, toCamelCase as snakeToCamelCase} from './util';
 
 export interface TranscodedRequest {
@@ -297,13 +298,13 @@ export function transcode(
   request: JSONObject,
   parsedOptions: ParsedOptionsType,
   requestFields?: {[k: string]: Field}
-): TranscodedRequest | undefined {
+): TranscodedRequest | GoogleError | undefined {
   const {requiredFields, optionalFields} =
     getFieldNameOnBehavior(requestFields);
   // all fields annotated as REQUIRED MUST be emitted in the body.
   for (const requiredField of requiredFields) {
     if (!(requiredField in request) || request[requiredField] === 'undefined') {
-      throw new Error(
+      return new GoogleError(
         `Required field ${requiredField} is not present in the request.`
       );
     }

test/browser-test/test.grpc-fallback.ts

@@ -23,6 +23,7 @@ import * as protobuf from 'protobufjs';
 import * as sinon from 'sinon';
 
 import * as fallback from '../../src/fallback';
+import {StreamArrayParser} from '../../src/streamArrayParser';
 import {echoProtoJson} from '../fixtures/echoProtoJson';
 import {EchoClient} from '../fixtures/google-gax-packaging-test-app/src/v1beta1/echo_client';
 
@@ -220,7 +221,7 @@ describe('grpc-fallback', () => {
     const request = {content: 'content' + new Date().toString()};
     const call = echoStub.echo(request, {}, {}, () => {});
 
-    call.cancel();
+    (call as StreamArrayParser).cancel();
 
     // @ts-ignore
     assert.strictEqual(createdAbortControllers[0].abortCalled, true);

test/unit/grpc-fallback.ts

@@ -28,6 +28,7 @@ import * as sinon from 'sinon';
 import {echoProtoJson} from '../fixtures/echoProtoJson';
 import {GrpcClient} from '../../src/fallback';
 import {GoogleError} from '../../src';
+import {StreamArrayParser} from '../../src/streamArrayParser';
 
 // @ts-ignore
 const hasAbortController = typeof AbortController !== 'undefined';
@@ -402,7 +403,7 @@ describe('grpc-fallback', () => {
     const request = {content: 'content' + new Date().toString()};
     const call = echoStub.echo(request, {}, {}, () => {});
 
-    call.cancel();
+    (call as StreamArrayParser).cancel();
 
     // @ts-ignore
     assert.strictEqual(createdAbortControllers[0].abortCalled, true);

test/unit/transcoding.ts

@@ -32,6 +32,7 @@ import {
   buildQueryStringComponents,
   requestChangeCaseAndCleanup,
   overrideHttpRules,
+  TranscodedRequest,
 } from '../../src/transcoding';
 import * as assert from 'assert';
 import {
@@ -42,6 +43,7 @@ import * as protobuf from 'protobufjs';
 import {testMessageJson} from '../fixtures/fallbackOptional';
 import {echoProtoJson} from '../fixtures/echoProtoJson';
 import {google} from '../../protos/http';
+import {GoogleError} from '../../src';
 
 describe('gRPC to HTTP transcoding', () => {
   const parsedOptions: ParsedOptionsType = [
@@ -594,7 +596,7 @@ describe('validate proto3 field with default value', () => {
     ];
     const transcoded = transcode(request, parsedOptions, badTestMessageFields);
     assert.deepStrictEqual(
-      transcoded?.url,
+      (transcoded as TranscodedRequest)?.url,
       'projects/test-project/contents/test-content'
     );
   });
@@ -620,9 +622,9 @@ describe('validate proto3 field with default value', () => {
       },
     ];
     for (const request of requests) {
-      assert.throws(
-        () => transcode(request, parsedOptions, testMessageFields),
-        Error
+      assert.ok(
+        transcode(request, parsedOptions, testMessageFields) instanceof
+          GoogleError
       );
     }
   });
@@ -640,8 +642,13 @@ describe('validate proto3 field with default value', () => {
       },
     ];
     const transcoded = transcode(request, parsedOptions, testMessageFields);
-    assert.deepStrictEqual(transcoded?.url, 'projects/test-project');
-    assert.deepStrictEqual(transcoded?.data, {content: 'test-content'});
+    assert.deepStrictEqual(
+      (transcoded as TranscodedRequest)?.url,
+      'projects/test-project'
+    );
+    assert.deepStrictEqual((transcoded as TranscodedRequest)?.data, {
+      content: 'test-content',
+    });
   });
   it('when body="*", unset optional field should remove from body', () => {
     const requests: RequestType[] = [
@@ -666,10 +673,10 @@ describe('validate proto3 field with default value', () => {
     for (const request of requests) {
       const transcoded = transcode(request, parsedOptions, testMessageFields);
       assert.deepStrictEqual(
-        transcoded?.url,
+        (transcoded as TranscodedRequest)?.url,
         'projects/test-project/contents/test-content'
       );
-      assert.deepStrictEqual(transcoded?.data, {});
+      assert.deepStrictEqual((transcoded as TranscodedRequest)?.data, {});
     }
   });
   it('unset optional fields should not appear in query params', () => {
@@ -697,9 +704,15 @@ describe('validate proto3 field with default value', () => {
     ];
     for (const request of requests) {
       const transcoded = transcode(request, parsedOptions, testMessageFields);
-      assert.deepStrictEqual(transcoded?.url, 'projects/test-project');
-      assert.deepStrictEqual(transcoded?.data, 'test-content');
-      assert.deepStrictEqual(transcoded.queryString, '');
+      assert.deepStrictEqual(
+        (transcoded as TranscodedRequest)?.url,
+        'projects/test-project'
+      );
+      assert.deepStrictEqual(
+        (transcoded as TranscodedRequest)?.data,
+        'test-content'
+      );
+      assert.deepStrictEqual((transcoded as TranscodedRequest).queryString, '');
     }
   });
 });