[GitHub] [thrift] fishy commented on a change in pull request #2298: THRIFT-5326: Expand TException interface in go library

[GitBox <gi...@apache.org>]

fishy commented on a change in pull request #2298:
URL: https://github.com/apache/thrift/pull/2298#discussion_r547523241



##########
File path: compiler/cpp/src/thrift/generate/t_go_generator.cc
##########
@@ -2700,8 +2707,8 @@ void t_go_generator::generate_service_server(t_service* tservice) {
     f_types_ << indent() << "func (p *" << serviceName
                << "Processor) Process(ctx context.Context, iprot, oprot thrift.TProtocol) (success bool, err "
                   "thrift.TException) {" << endl;
-    f_types_ << indent() << "  name, _, seqId, err := iprot.ReadMessageBegin(ctx)" << endl;
-    f_types_ << indent() << "  if err != nil { return false, err }" << endl;
+    f_types_ << indent() << "  name, _, seqId, err2 := iprot.ReadMessageBegin(ctx)" << endl;

Review comment:
       Note: all the compiler changes starting from this line are because in Process function we specified the returned error type to be `TException` instead of just `error`. I'm not sure why is that, if we can make another breaking change to `TProcessor` and `TProcessorFunction` these changes can be avoided.

##########
File path: lib/go/thrift/exception.go
##########
@@ -26,19 +26,86 @@ import (
 // Generic Thrift exception
 type TException interface {
 	error
+
+	TExceptionType() TExceptionType
 }
 
 // Prepends additional information to an error without losing the Thrift exception interface
 func PrependError(prepend string, err error) error {
-	if t, ok := err.(TTransportException); ok {
-		return NewTTransportException(t.TypeId(), prepend+t.Error())
+	msg := prepend + err.Error()
+
+	if te, ok := err.(TException); ok {
+		switch te.TExceptionType() {
+		case TExceptionTypeTransport:
+			if t, ok := err.(TTransportException); ok {
+				return NewTTransportException(t.TypeId(), msg)
+			}
+		case TExceptionTypeProtocol:
+			if t, ok := err.(TProtocolException); ok {
+				return NewTProtocolExceptionWithType(t.TypeId(), errors.New(msg))
+			}
+		case TExceptionTypeApplication:
+			if t, ok := err.(TApplicationException); ok {
+				return NewTApplicationException(t.TypeId(), msg)
+			}
+		}
+
+		return wrappedTException{
+			err:            errors.New(msg),
+			tExceptionType: te.TExceptionType(),
+		}
+	}
+
+	return errors.New(msg)
+}
+
+// TExceptionType is an enum type to categorize different "subclasses" of TExceptions.
+type TExceptionType byte
+
+// TExceptionType values
+const (
+	TExceptionTypeUnknown     TExceptionType = iota
+	TExceptionTypeCompiled                   // TExceptions defined in thrift files and generated by thrift compiler

Review comment:
       I'm open to suggestions on this name :)




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