Expunge error codes that shouldn't be returned from library (#1875)

- Per 9d0bc30edb/doc/statuscodes.md
- Relevant issue: #1672

transport/handler_server.go

@@ -98,7 +98,7 @@ func NewServerHandlerTransport(w http.ResponseWriter, r *http.Request, stats sta
 		for _, v := range vv {
 			v, err := decodeMetadataHeader(k, v)
 			if err != nil {
-				return nil, streamErrorf(codes.InvalidArgument, "malformed binary metadata: %v", err)
+				return nil, streamErrorf(codes.Internal, "malformed binary metadata: %v", err)
 			}
 			metakv = append(metakv, k, v)
 		}

transport/http_util.go

@@ -70,7 +70,7 @@ var (
 		http2.ErrCodeConnect:            codes.Internal,
 		http2.ErrCodeEnhanceYourCalm:    codes.ResourceExhausted,
 		http2.ErrCodeInadequateSecurity: codes.PermissionDenied,
-		http2.ErrCodeHTTP11Required:     codes.FailedPrecondition,
+		http2.ErrCodeHTTP11Required:     codes.Internal,
 	}
 	statusCodeConvTab = map[codes.Code]http2.ErrCode{
 		codes.Internal:          http2.ErrCodeInternal,
@@ -283,7 +283,7 @@ func (d *decodeState) processHeaderField(f hpack.HeaderField) error {
 	case "content-type":
 		contentSubtype, validContentType := contentSubtype(f.Value)
 		if !validContentType {
-			return streamErrorf(codes.FailedPrecondition, "transport: received the unexpected content-type %q", f.Value)
+			return streamErrorf(codes.Internal, "transport: received the unexpected content-type %q", f.Value)
 		}
 		d.contentSubtype = contentSubtype
 		// TODO: do we want to propagate the whole content-type in the metadata,

transport/transport_test.go

@@ -1545,8 +1545,8 @@ func TestInvalidHeaderField(t *testing.T) {
 	}
 	p := make([]byte, http2MaxFrameLen)
 	_, err = s.trReader.(*transportReader).Read(p)
-	if se, ok := err.(StreamError); !ok || se.Code != codes.FailedPrecondition || !strings.Contains(err.Error(), expectedInvalidHeaderField) {
-		t.Fatalf("Read got error %v, want error with code %s and contains %q", err, codes.FailedPrecondition, expectedInvalidHeaderField)
+	if se, ok := err.(StreamError); !ok || se.Code != codes.Internal || !strings.Contains(err.Error(), expectedInvalidHeaderField) {
+		t.Fatalf("Read got error %v, want error with code %s and contains %q", err, codes.Internal, expectedInvalidHeaderField)
 	}
 	ct.Close()
 	server.stop()