3 files changed, 34 insertions, 3 deletions

diff --git a/include/grpc++/impl/codegen/call.h b/include/grpc++/impl/codegen/call.h
index af2c2b510c..e581049e7f 100644
--- a/include/grpc++/impl/codegen/call.h
+++ b/include/grpc++/impl/codegen/call.h
@@ -558,10 +558,12 @@ class CallOpRecvInitialMetadata {
 
 class CallOpClientRecvStatus {
  public:
-  CallOpClientRecvStatus() : recv_status_(nullptr) {}
+  CallOpClientRecvStatus()
+      : recv_status_(nullptr), debug_error_string_(nullptr) {}
 
   void ClientRecvStatus(ClientContext* context, Status* status) {
-    metadata_map_ = &context->trailing_metadata_;
+    client_context_ = context;
+    metadata_map_ = &client_context_->trailing_metadata_;
     recv_status_ = status;
     error_message_ = g_core_codegen_interface->grpc_empty_slice();
   }
@@ -574,7 +576,7 @@ class CallOpClientRecvStatus {
     op->data.recv_status_on_client.trailing_metadata = metadata_map_->arr();
     op->data.recv_status_on_client.status = &status_code_;
     op->data.recv_status_on_client.status_details = &error_message_;
-    op->data.recv_status_on_client.error_string = nullptr;
+    op->data.recv_status_on_client.error_string = &debug_error_string_;
     op->flags = 0;
     op->reserved = NULL;
   }
@@ -592,13 +594,20 @@ class CallOpClientRecvStatus {
                            grpc::string(GRPC_SLICE_START_PTR(error_message_),
                                         GRPC_SLICE_END_PTR(error_message_)),
                            binary_error_details);
+    client_context_->set_debug_error_string(
+        debug_error_string_ != nullptr ? debug_error_string_ : "");
     g_core_codegen_interface->grpc_slice_unref(error_message_);
+    if (debug_error_string_ != nullptr) {
+      g_core_codegen_interface->gpr_free((void*)debug_error_string_);
+    }
     recv_status_ = nullptr;
   }
 
  private:
+  ClientContext* client_context_;
   MetadataMap* metadata_map_;
   Status* recv_status_;
+  const char* debug_error_string_;
   grpc_status_code status_code_;
   grpc_slice error_message_;
 };
diff --git a/include/grpc++/impl/codegen/client_context.h b/include/grpc++/impl/codegen/client_context.h
index 22b581cbc5..61d97ce818 100644
--- a/include/grpc++/impl/codegen/client_context.h
+++ b/include/grpc++/impl/codegen/client_context.h
@@ -348,6 +348,13 @@ class ClientContext {
   /// Applications never need to call this method.
   grpc_call* c_call() { return call_; }
 
+  /// EXPERIMENTAL debugging API
+  ///
+  /// if status is not ok() for an RPC, this will return a detailed string
+  /// of the gRPC Core error that led to the failure. It should not be relied
+  /// upon for anything other than gaining more debug data in failure cases.
+  grpc::string debug_error_string() const { return debug_error_string_; }
+
  private:
   // Disallow copy and assign.
   ClientContext(const ClientContext&);
@@ -374,6 +381,11 @@ class ClientContext {
   template <class InputMessage, class OutputMessage>
   friend class ::grpc::internal::BlockingUnaryCallImpl;
 
+  // Used by friend class CallOpClientRecvStatus
+  void set_debug_error_string(const grpc::string& debug_error_string) {
+    debug_error_string_ = debug_error_string;
+  }
+
   grpc_call* call() const { return call_; }
   void set_call(grpc_call* call, const std::shared_ptr<Channel>& channel);
 
@@ -412,6 +424,8 @@ class ClientContext {
 
   grpc_compression_algorithm compression_algorithm_;
   bool initial_metadata_corked_;
+
+  grpc::string debug_error_string_;
 };
 
 }  // namespace grpc
diff --git a/test/cpp/end2end/end2end_test.cc b/test/cpp/end2end/end2end_test.cc
index c71034bbe8..1d63f395dc 100644
--- a/test/cpp/end2end/end2end_test.cc
+++ b/test/cpp/end2end/end2end_test.cc
@@ -741,6 +741,7 @@ TEST_P(End2endTest, RequestStreamOneRequest) {
   Status s = stream->Finish();
   EXPECT_EQ(response.message(), request.message());
   EXPECT_TRUE(s.ok());
+  EXPECT_TRUE(context.debug_error_string().empty());
 }
 
 TEST_P(End2endTest, RequestStreamOneRequestWithCoalescingApi) {
@@ -1258,6 +1259,13 @@ TEST_P(End2endTest, ExpectErrorTest) {
     EXPECT_EQ(iter->code(), s.error_code());
     EXPECT_EQ(iter->error_message(), s.error_message());
     EXPECT_EQ(iter->binary_error_details(), s.error_details());
+    EXPECT_TRUE(context.debug_error_string().find("created") !=
+                std::string::npos);
+    EXPECT_TRUE(context.debug_error_string().find("file") != std::string::npos);
+    EXPECT_TRUE(context.debug_error_string().find("line") != std::string::npos);
+    EXPECT_TRUE(context.debug_error_string().find("status") !=
+                std::string::npos);
+    EXPECT_TRUE(context.debug_error_string().find("13") != std::string::npos);
   }
 }