Minor: wrap the inner error on retried transactions and return when deadline exceeded

src/transaction.js

@@ -17,6 +17,7 @@
 'use strict';
 
 const {promisifyAll} = require('@google-cloud/promisify');
+const common = require('@google-cloud/common-grpc');
 const extend = require('extend');
 const gax = require('google-gax');
 const is = require('is');
@@ -40,6 +41,11 @@ const TransactionRequest = require('./transaction-request');
  */
 const UNKNOWN = 2;
 
+/**
+ * the gRPC `DEADLINE_EXCEEDED` error code.
+ */
+const DEADLINE_EXCEEDED = 4;
+
 /**
  * The gRPC `ABORTED` error code.
  *
@@ -720,10 +726,13 @@ class Transaction extends TransactionRequest {
    * @return {object}
    */
   static createDeadlineError_(err) {
-    return extend({}, err, {
-      code: 4,
-      message: 'Deadline for Transaction exceeded.',
-    });
+    let apiError = new common.util.ApiError(
+      'Deadline for Transaction exceeded.'
+    );
+    apiError.code = DEADLINE_EXCEEDED;
+    apiError.errors = [err];
+
+    return apiError;
   }
   /**
    * Extracts retry delay and formats into milliseconds.

test/transaction.js

@@ -196,16 +196,14 @@ describe('Transaction', function() {
         b: 'b',
       };
 
-      const expectedError = {
-        code: 4,
-        message: 'Deadline for Transaction exceeded.',
-        a: 'a',
-        b: 'b',
-      };
-
       const formattedError = Transaction.createDeadlineError_(originalError);
 
-      assert.deepStrictEqual(expectedError, formattedError);
+      assert.strictEqual(formattedError.code, 4);
+      assert.strictEqual(
+        formattedError.message,
+        'Deadline for Transaction exceeded.'
+      );
+      assert.deepStrictEqual(originalError, formattedError.errors[0]);
       assert.notStrictEqual(originalError, formattedError);
     });
   });