Treat mismatched length-delimited repeated Group tags as unknown fields in upb.

PiperOrigin-RevId: 919206177

Author: Rachel Goldfinger

upb/wire/decode.c

@@ -861,7 +861,7 @@ static int _upb_Decoder_GetDelimitedOp(upb_Decoder* d, const upb_MiniTable* mt,
       [kRepeatedBase + kUpb_FieldType_Fixed32] = OP_FIXPCK_LG2(2),
       [kRepeatedBase + kUpb_FieldType_Bool] = OP_VARPCK_LG2(0),
       [kRepeatedBase + kUpb_FieldType_String] = kUpb_DecodeOp_String,
-      [kRepeatedBase + kUpb_FieldType_Group] = kUpb_DecodeOp_SubMessage,
+      [kRepeatedBase + kUpb_FieldType_Group] = kUpb_DecodeOp_UnknownField,
       [kRepeatedBase + kUpb_FieldType_Message] = kUpb_DecodeOp_SubMessage,
       [kRepeatedBase + kUpb_FieldType_Bytes] = kUpb_DecodeOp_Bytes,
       [kRepeatedBase + kUpb_FieldType_UInt32] = OP_VARPCK_LG2(2),

upb/wire/decode_test.cc

@@ -471,6 +471,43 @@ TEST(DecodeTest, MaxDepthPayloadParsesSuccessfully) {
   }
 }
 
+TEST(DecodeTest, DecodeGroupFieldFromDelimitedWireFormatAsUnknown) {
+  upb::Arena mt_arena;
+  upb::Arena msg_arena;
+
+  // 1. Create Parent MiniTable containing a repeated Group field directly.
+  auto [parent_mt, parent_field] =
+      test::MiniTable::MakeSingleFieldTable<test::field_types::Group>(
+          5, kUpb_DecodeFast_Repeated, mt_arena.ptr());
+
+  // 2. Build length-delimited wire payload for Group field 5:
+  // Tag 5 Delimited = 42 (0x2a), length = 2, child field 1 = 123 ("\x08\x7b").
+  std::string payload("\x2a\x02\x08\x7b", 4);
+
+  // 3. Parse the payload into Parent Message.
+  upb_Message* parent_msg = upb_Message_New(parent_mt, msg_arena.ptr());
+  upb_DecodeStatus result =
+      upb_Decode(payload.data(), payload.size(), parent_msg, parent_mt, nullptr,
+                 0, msg_arena.ptr());
+
+  // 4. Verify parsing succeeded cleanly.
+  ASSERT_EQ(result, kUpb_DecodeStatus_Ok) << upb_DecodeStatus_String(result);
+
+  // 5. Verify repeated Group field 5 was NOT populated as a known field.
+  const upb_Array* arr = upb_Message_GetArray(parent_msg, parent_field);
+  EXPECT_EQ(arr, nullptr);
+
+  // 6. Verify the wire payload was instead preserved inside the Unknown field
+  // set.
+  EXPECT_TRUE(upb_Message_HasUnknown(parent_msg));
+
+  uintptr_t iter = kUpb_Message_UnknownBegin;
+  upb_StringView data;
+  ASSERT_TRUE(upb_Message_NextUnknown(parent_msg, &data, &iter));
+  EXPECT_EQ(absl::string_view(data.data, data.size), payload);
+  EXPECT_FALSE(upb_Message_NextUnknown(parent_msg, &data, &iter));
+}
+
 }  // namespace
 
 }  // namespace test

upb/wire/test_util/field_types.h

@@ -293,7 +293,16 @@ struct ClosedEnum {
   }
 };
 
-// TODO: Group
+struct Group {
+  using Value = std::string;
+  static constexpr upb_FieldType kFieldType = kUpb_FieldType_Group;
+  static constexpr absl::string_view kName = "Group";
+  static constexpr upb_DecodeFast_Type kFastType = kUpb_DecodeFast_Message;
+
+  static wire_types::WireValue WireValue(std::string value) {
+    return wire_types::Delimited(value);
+  }
+};
 
 }  // namespace field_types
 

upb/wire/test_util/make_mini_table.cc

@@ -100,7 +100,7 @@ MiniTable::MakeSingleFieldTable(int field_number, upb_FieldType type,
     ABSL_CHECK(ok);
   }
 #if UPB_FASTTABLE
-  if (field_number < (1 << 11)) {
+  if (field_number < (1 << 11) && type != kUpb_FieldType_Group) {
     ABSL_CHECK_EQ(HasFastTableEntry(table, field),
                   UPB_DECODEFAST_ISENABLED(fast_type, cardinality,
                                            kUpb_DecodeFast_Tag1Byte))