Surface transaction errors in browser (#2017)

Author: Brian Chen

packages/firestore/src/platform_browser/webchannel_connection.ts

@@ -31,8 +31,8 @@ import { DatabaseId, DatabaseInfo } from '../core/database_info';
 import { SDK_VERSION } from '../core/version';
 import { Connection, Stream } from '../remote/connection';
 import {
-  mapCodeFromHttpStatus,
-  mapCodeFromRpcStatus
+  mapCodeFromRpcStatus,
+  mapCodeFromHttpResponseErrorStatus
 } from '../remote/rpc_error';
 import { StreamBridge } from '../remote/stream_bridge';
 import { assert, fail } from '../util/assert';
@@ -123,20 +123,25 @@ export class WebChannelConnection implements Connection {
                 xhr.getResponseText()
               );
               if (status > 0) {
-                const response = xhr.getResponseJson().error;
-                if (!!response) {
-                  const serverError = response.status
-                    .toLowerCase()
-                    .replace('_', '-');
-                  const firestoreError: Code =
-                    Object.values(Code).indexOf(serverError) >= 0
-                      ? (serverError as Code)
-                      : Code.UNKNOWN;
-                  reject(new FirestoreError(firestoreError, response.message));
+                const responseError = xhr.getResponseJson().error;
+                if (
+                  !!responseError &&
+                  !!responseError.status &&
+                  !!responseError.message
+                ) {
+                  const firestoreErrorCode = mapCodeFromHttpResponseErrorStatus(
+                    responseError.status
+                  );
+                  reject(
+                    new FirestoreError(
+                      firestoreErrorCode,
+                      responseError.message
+                    )
+                  );
                 } else {
                   reject(
                     new FirestoreError(
-                      mapCodeFromHttpStatus(status),
+                      Code.UNKNOWN,
                       'Server responded with status ' + xhr.getStatus()
                     )
                   );

packages/firestore/src/remote/rpc_error.ts

@@ -298,3 +298,18 @@ export function mapCodeFromHttpStatus(status: number): Code {
       return Code.UNKNOWN;
   }
 }
+
+/**
+ * Converts an HTTP response's error status to the equivalent error code.
+ *
+ * @param status An HTTP error response status ("FAILED_PRECONDITION",
+ * "UNKNOWN", etc.)
+ * @returns The equivalent Code. Non-matching responses are mapped to
+ *     Code.UNKNOWN.
+ */
+export function mapCodeFromHttpResponseErrorStatus(status: string): Code {
+  const serverError = status.toLowerCase().replace('_', '-');
+  return Object.values(Code).indexOf(serverError as Code) >= 0
+    ? (serverError as Code)
+    : Code.UNKNOWN;
+}