Update set_alias to use FindFieldByNumber

PiperOrigin-RevId: 688120291

hpb_generator/gen_accessors.cc

@@ -285,7 +285,7 @@ void WriteAccessorsInSource(const protobuf::Descriptor* desc, Context& ctx) {
                 ABSL_CHECK_EQ(arena_, hpb::interop::upb::GetArena(target));
                 upb_Message_SetBaseFieldMessage(
                     UPB_UPCAST(msg_),
-                    upb_MiniTable_GetFieldByIndex($7::minitable(), $8),
+                    upb_MiniTable_FindFieldByNumber($7::minitable(), $8),
                     hpb::interop::upb::GetMessage(target));
               }
             )cc",
@@ -293,7 +293,7 @@ void WriteAccessorsInSource(const protobuf::Descriptor* desc, Context& ctx) {
             resolved_field_name,
             upb::generator::CApiMessageType(desc->full_name()),
             MessageBaseType(field, /* maybe_const */ false), resolved_upbc_name,
-            arena_expression, ClassName(desc), field->index());
+            arena_expression, ClassName(desc), field->number());
       }
     }
   }

hpb_generator/tests/set_alias.proto

@@ -14,8 +14,9 @@ message Child {
 }
 
 message Parent {
-  optional int32 x = 1;
+  optional int32 x = 2;
-  optional Child child = 2;
+  optional Child child = 3;
+  optional int64 out_of_order = 1;  // set_alias must work regardless of order
 }
 
 message ParentWithRepeated {

hpb_generator/tests/test_generated.cc

@@ -1284,6 +1284,18 @@ TEST(CppGeneratedCode, SetAlias) {
             hpb::interop::upb::GetMessage(parent1.child()));
 }
 
+TEST(CppGeneratedCode, SetAliasFieldsOutofOrder) {
+  hpb::Arena arena;
+  auto child = hpb::CreateMessage<Child>(arena);
+  child.set_peeps(12);
+  auto parent1 = hpb::CreateMessage<Parent>(arena);
+  auto parent2 = hpb::CreateMessage<Parent>(arena);
+  parent1.set_alias_child(child);
+  parent2.set_alias_child(child);
+  ASSERT_EQ(parent1.child()->peeps(), parent2.child()->peeps());
+  ASSERT_EQ(parent1.child()->peeps(), 12);
+}
+
 TEST(CppGeneratedCode, SetAliasFailsForDifferentArena) {
   hpb::Arena arena;
   auto child = hpb::CreateMessage<Child>(arena);