Incremental migration of message.cc to Emit

PiperOrigin-RevId: 530452483

src/google/protobuf/compiler/cpp/message.cc

@@ -1073,40 +1073,46 @@ void MessageGenerator::GenerateOneofMemberHasBits(const FieldDescriptor* field,
 void MessageGenerator::GenerateFieldClear(const FieldDescriptor* field,
                                           bool is_inline, io::Printer* p) {
   auto t = p->WithVars(MakeTrackerCalls(field, options_));
-  Formatter format(p);
-
-  // Generate clear_$name$().
-  if (is_inline) {
-    format("inline ");
-  }
-  format("void $classname$::clear_$name$() {\n");
-
-  format.Indent();
-
-  if (field->real_containing_oneof()) {
-    // Clear this field only if it is the active field in this oneof,
-    // otherwise ignore
-    auto t = p->WithVars(MakeTrackerCalls(field, options_));
-    format("if ($has_field$) {\n");
-    format.Indent();
-    field_generators_.get(field).GenerateClearingCode(p);
-    format("clear_has_$oneof_name$();\n");
-    format.Outdent();
-    format("}\n");
-  } else {
-    if (ShouldSplit(field, options_)) {
-      format("if (IsSplitMessageDefault()) return;\n");
-    }
-    field_generators_.get(field).GenerateClearingCode(p);
-    if (HasHasbit(field)) {
-      int has_bit_index = HasBitIndex(field);
-      auto v = p->WithVars(HasbitVars(has_bit_index));
-      format("$has_bits$[$has_array_index$] &= ~$has_mask$;\n");
-    }
-  }
-  format("$annotate_clear$");
-  format.Outdent();
-  format("}\n");
+  p->Emit({{"inline", is_inline ? "inline" : ""},
+           {"body",
+            [&] {
+              if (field->real_containing_oneof()) {
+                // Clear this field only if it is the active field in this
+                // oneof, otherwise ignore
+                p->Emit(
+                    {{"clearing_code",
+                      [&] {
+                        field_generators_.get(field).GenerateClearingCode(p);
+                      }}},
+                    R"cc(
+                      if ($has_field$) {
+                        $clearing_code$;
+                        clear_has_$oneof_name$();
+                      }
+                    )cc");
+              } else {
+                // TODO(b/281513105): figure out if early return breaks tracking
+                if (ShouldSplit(field, options_)) {
+                  p->Emit(R"cc(
+                    if (IsSplitMessageDefault()) return;
+                  )cc");
+                }
+                field_generators_.get(field).GenerateClearingCode(p);
+                if (HasHasbit(field)) {
+                  int has_bit_index = HasBitIndex(field);
+                  auto v = p->WithVars(HasbitVars(has_bit_index));
+                  p->Emit(R"cc(
+                    $has_bits$[$has_array_index$] &= ~$has_mask$;
+                  )cc");
+                }
+              }
+            }}},
+          R"cc(
+            $inline $void $classname$::clear_$name$() {
+              $body$;
+              $annotate_clear$;
+            }
+          )cc");
 }
 
 void MessageGenerator::GenerateFieldAccessorDefinitions(io::Printer* p) {