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

src/fallbackRest.ts

@@ -45,11 +45,13 @@ export function encodeRequest(
  if (typeof json !== 'object' || Array.isArray(json)) {
  throw new Error(`Request to RPC ${rpc.name} must be an object.`);
  }
+
  const transcoded = transcode(
  json,
  rpc.parsedOptions,
  rpc.resolvedRequestType!.fields
  );
+
  if (!transcoded) {
  throw new Error(
  `Cannot build HTTP request for ${JSON.stringify(json)}, method: ${

src/fallbackServiceStub.ts

@@ -86,19 +86,29 @@ export function generateServiceStub(
  // We cannot use async-await in this function because we need to return the canceller object as soon as possible.
  // Using plain old promises instead.
 
+ let fetchParameters: FetchParameters;
+ try {
+ fetchParameters = requestEncoder(
+ rpc,
+ protocol,
+ servicePath,
+ servicePort,
+ request
+ );
+ } catch (err) {
+ // we could not encode parameters; pass error to the callback
+ // and return a no-op canceler object.
+ callback(err);
+ return {
+ cancel() {},
+ };
+ }
+
  const cancelController = hasAbortController()
  ? new AbortController()
  : new NodeAbortController();
  const cancelSignal = cancelController.signal as AbortSignal;
  let cancelRequested = false;
-
- const fetchParameters = requestEncoder(
- rpc,
- protocol,
- servicePath,
- servicePort,
- request
- );
  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, Type} from 'protobufjs';
 import {google} from '../protos/http';
+import {GoogleError} from './googleError';
 import {camelToSnakeCase, toCamelCase as snakeToCamelCase} from './util';
 
 export interface TranscodedRequest {
@@ -340,7 +341,7 @@ export function transcode(
  // 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(
+ throw new GoogleError(
  `Required field ${requiredField} is not present in the request.`
  );
  }

test/unit/transcoding.ts

@@ -32,6 +32,7 @@ import {
  buildQueryStringComponents,
  requestChangeCaseAndCleanup,
  overrideHttpRules,
+ TranscodedRequest,
 } from '../../src/transcoding';
 import * as assert from 'assert';
 import {
@@ -615,7 +616,7 @@ 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'
  );
  });
@@ -633,7 +634,7 @@ describe('validate proto3 field with default value', () => {
  ];
  assert.throws(
  () => transcode(request, parsedOptions, testMessageFields),
- Error
+ /Error: Required field content is not present in the request/
  );
  });
  it('when body="*", all required field should emitted in body', () => {
@@ -650,8 +651,13 @@ 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 request: RequestType = {
@@ -668,10 +674,10 @@ describe('validate proto3 field with default value', () => {
  ];
  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', () => {
  const request: RequestType = {
@@ -690,9 +696,15 @@ describe('validate proto3 field with default value', () => {
  },
  ];
  const transcoded = transcode(request, parsedOptions, testMessageFields);
- assert.deepStrictEqual(transcoded?.url, 'projects/test-project');
- assert.deepStrictEqual(transcoded?.data, 'test-content');
- assert.strictEqual(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, '');
  });
 });