4 files changed, 52 insertions, 5 deletions

diff --git a/src/objective-c/GRPCClient/private/GRPCWrappedCall.m b/src/objective-c/GRPCClient/private/GRPCWrappedCall.m
index f28e494868..7781d27ca4 100644
--- a/src/objective-c/GRPCClient/private/GRPCWrappedCall.m
+++ b/src/objective-c/GRPCClient/private/GRPCWrappedCall.m
@@ -187,6 +187,7 @@
   grpc_slice _details;
   size_t _detailsCapacity;
   grpc_metadata_array _trailers;
+  const char *_errorString;
 }
 
 - (instancetype)init {
@@ -200,6 +201,7 @@
     _op.data.recv_status_on_client.status_details = &_details;
     grpc_metadata_array_init(&_trailers);
     _op.data.recv_status_on_client.trailing_metadata = &_trailers;
+    _op.data.recv_status_on_client.error_string = &_errorString;
     if (handler) {
       // Prevent reference cycle with _handler
       __weak typeof(self) weakSelf = self;
@@ -207,8 +209,9 @@
         __strong typeof(self) strongSelf = weakSelf;
         if (strongSelf) {
           char *details = grpc_slice_to_c_string(strongSelf->_details);
-          NSError *error =
-              [NSError grpc_errorFromStatusCode:strongSelf->_statusCode details:details];
+          NSError *error = [NSError grpc_errorFromStatusCode:strongSelf->_statusCode
+                                                     details:details
+                                                 errorString:strongSelf->_errorString];
           NSDictionary *trailers =
               [NSDictionary grpc_dictionaryFromMetadataArray:strongSelf->_trailers];
           handler(error, trailers);
@@ -223,6 +226,7 @@
 - (void)dealloc {
   grpc_metadata_array_destroy(&_trailers);
   grpc_slice_unref(_details);
+  gpr_free((void *)_errorString);
 }
 
 @end
diff --git a/src/objective-c/GRPCClient/private/NSError+GRPC.h b/src/objective-c/GRPCClient/private/NSError+GRPC.h
index e96b7297c2..a63e76ee4d 100644
--- a/src/objective-c/GRPCClient/private/NSError+GRPC.h
+++ b/src/objective-c/GRPCClient/private/NSError+GRPC.h
@@ -24,5 +24,7 @@
  * Returns nil if the status code is OK. Otherwise, a NSError whose code is one of |GRPCErrorCode|
  * and whose domain is |kGRPCErrorDomain|.
  */
-+ (instancetype)grpc_errorFromStatusCode:(grpc_status_code)statusCode details:(char *)details;
++ (instancetype)grpc_errorFromStatusCode:(grpc_status_code)statusCode
+                                 details:(char *)details
+                             errorString:(const char *)errorString;
 @end
diff --git a/src/objective-c/GRPCClient/private/NSError+GRPC.m b/src/objective-c/GRPCClient/private/NSError+GRPC.m
index c2e65e4d8a..199b2ebb6c 100644
--- a/src/objective-c/GRPCClient/private/NSError+GRPC.m
+++ b/src/objective-c/GRPCClient/private/NSError+GRPC.m
@@ -23,13 +23,19 @@
 NSString *const kGRPCErrorDomain = @"io.grpc";
 
 @implementation NSError (GRPC)
-+ (instancetype)grpc_errorFromStatusCode:(grpc_status_code)statusCode details:(char *)details {
++ (instancetype)grpc_errorFromStatusCode:(grpc_status_code)statusCode
+                                 details:(char *)details
+                             errorString:(const char *)errorString {
   if (statusCode == GRPC_STATUS_OK) {
     return nil;
   }
   NSString *message = [NSString stringWithCString:details encoding:NSUTF8StringEncoding];
+  NSString *debugMessage = [NSString stringWithCString:errorString encoding:NSUTF8StringEncoding];
   return [NSError errorWithDomain:kGRPCErrorDomain
                              code:statusCode
-                         userInfo:@{NSLocalizedDescriptionKey : message}];
+                         userInfo:@{
+                           NSLocalizedDescriptionKey : message,
+                           NSDebugDescriptionErrorKey : debugMessage
+                         }];
 }
 @end
diff --git a/src/objective-c/tests/GRPCClientTests.m b/src/objective-c/tests/GRPCClientTests.m
index 2a169800a0..a0de8ba899 100644
--- a/src/objective-c/tests/GRPCClientTests.m
+++ b/src/objective-c/tests/GRPCClientTests.m
@@ -591,4 +591,39 @@ static GRPCProtoMethod *kFullDuplexCallMethod;
   [self testTimeoutBackoffWithTimeout:0.3 Backoff:0.7];
 }
 
+- (void)testErrorDebugInformation {
+  __weak XCTestExpectation *expectation = [self expectationWithDescription:@"RPC unauthorized."];
+
+  RMTSimpleRequest *request = [RMTSimpleRequest message];
+  request.fillUsername = YES;
+  request.fillOauthScope = YES;
+  GRXWriter *requestsWriter = [GRXWriter writerWithValue:[request data]];
+
+  GRPCCall *call = [[GRPCCall alloc] initWithHost:kRemoteSSLHost
+                                             path:kUnaryCallMethod.HTTPPath
+                                   requestsWriter:requestsWriter];
+
+  call.oauth2AccessToken = @"bogusToken";
+
+  id<GRXWriteable> responsesWriteable =
+      [[GRXWriteable alloc] initWithValueHandler:^(NSData *value) {
+        XCTFail(@"Received unexpected response: %@", value);
+      }
+          completionHandler:^(NSError *errorOrNil) {
+            XCTAssertNotNil(errorOrNil, @"Finished without error!");
+            NSDictionary *userInfo = errorOrNil.userInfo;
+            NSString *debugInformation = userInfo[NSDebugDescriptionErrorKey];
+            XCTAssertNotNil(debugInformation);
+            XCTAssertNotEqual([debugInformation length], 0);
+            NSString *challengeHeader = call.oauth2ChallengeHeader;
+            XCTAssertGreaterThan(challengeHeader.length, 0, @"No challenge in response headers %@",
+                                 call.responseHeaders);
+            [expectation fulfill];
+          }];
+
+  [call startWithWriteable:responsesWriteable];
+
+  [self waitForExpectationsWithTimeout:TEST_TIMEOUT handler:nil];
+}
+
 @end