Add zero_override field option

README.md

@@ -1,6 +1,6 @@
 ## Fork of [Protobuf Golang](https://github.com/protocolbuffers/protobuf-go) specialized for type generation
 
-This package supposed to focus on type generation based on proto file. 
+This package supposed to focus on type generation based on proto file.
 
 ### Features compared to original repository
 
@@ -41,8 +41,9 @@ message TimeTime {}
 
 #### Important
 
-Currently the overwritten FieldOptions (go_type, go_import, go_import_alias) must be paired with these numbers:
+Currently the overwritten FieldOptions (go_type, go_import, go_import_alias, go_zero_override) must be paired with these numbers:
 go_type = 1001
 go_import = 1002
 go_import_alias = 1003
-Because `protoc` can't process the extended options, so we can't find the by name, just by place. 
+go_zero_override = 1004
+Because `protoc` can't process the extended options, so we can't find the by name, just by place.

cmd/protoc-gen-go/internal_gengo/main.go

@@ -36,9 +36,10 @@ const (
 )
 
 type overrideParams struct {
-	goType        string
-	goImport      string
-	goImportAlias string
+	goType         string
+	goImport       string
+	goImportAlias  string
+	goZeroOverride string
 }
 
 // overrideFields stores all the found messages which are created to override types
@@ -197,6 +198,10 @@ func processExtensions(field *protogen.Field) (overrideParams, bool) {
 		case impl.FieldOptionGoImportAlias:
 			override.goImportAlias = ex.Value().String()
 			ok = true
+		case impl.FieldOptionGoZeroOverride:
+			log.Log("processExtensions:: zero override found!")
+			override.goZeroOverride = ex.Value().String()
+			ok = true
 		}
 	}
 	return override, ok
@@ -219,6 +224,9 @@ func processUninterpretedOptions(field *protogen.Field) (overrideParams, bool) {
 				case impl.FieldOptionGoImportAlias:
 					override.goImportAlias = string(o.GetStringValue())
 					ok = true
+				case impl.FieldOptionGoZeroOverride:
+					override.goZeroOverride = string(o.GetStringValue())
+					ok = true
 				}
 			}
 		}
@@ -523,7 +531,9 @@ func genMessageField(g *protogen.GeneratedFile, f *fileInfo, m *messageInfo, fie
 	if pointer {
 		goType = "*" + goType
 	}
-	goType, _ = goTypeOverride(goType, m.GoIdent.GoName, field.GoName)
+	if overrideParam, ok := goTypeOverride(m.GoIdent.GoName, field.GoName); ok {
+		goType = overrideParam.goType
+	}
 	tags := structTags{
 		{"protobuf", fieldProtobufTagValue(field)},
 		{"json", fieldJSONTagValue(field)},
@@ -563,7 +573,9 @@ func genMessageDefaultDecls(g *protogen.GeneratedFile, f *fileInfo, m *messageIn
 		}
 		name := "Default_" + m.GoIdent.GoName + "_" + field.GoName
 		goType, _ := fieldGoType(g, f, field)
-		goType, _ = goTypeOverride(goType, m.GoIdent.GoName, field.GoName)
+		if overrideParam, ok := goTypeOverride(m.GoIdent.GoName, field.GoName); ok {
+			goType = overrideParam.goType
+		}
 		defVal := field.Desc.Default()
 		switch field.Desc.Kind() {
 		case protoreflect.StringKind:
@@ -686,9 +698,11 @@ func genMessageGetterMethods(g *protogen.GeneratedFile, f *fileInfo, m *messageI
 
 		// Getter for message field.
 		goType, pointer := fieldGoType(g, f, field)
-		var overwritten bool
-		goType, overwritten = goTypeOverride(goType, m.GoIdent.GoName, field.GoName)
-		defaultValue := fieldDefaultValue(g, f, m, field, goType, overwritten)
+		overrideParam, overwritten := goTypeOverride(m.GoIdent.GoName, field.GoName)
+		if overwritten {
+			goType = overrideParam.goType
+		}
+		defaultValue := fieldDefaultValue(g, f, m, field, goType, overrideParam, overwritten)
 		g.Annotate(m.GoIdent.GoName+".Get"+field.GoName, field.Location)
 		leadingComments := appendDeprecationSuffix("",
 			field.Desc.Options().(*descriptorpb.FieldOptions).GetDeprecated())
@@ -814,8 +828,12 @@ func fieldProtobufTagValue(field *protogen.Field) string {
 	return tag.Marshal(field.Desc, enumName)
 }
 
-func fieldDefaultValue(g *protogen.GeneratedFile, f *fileInfo, m *messageInfo, field *protogen.Field, goType string, overwritten bool) string {
+func fieldDefaultValue(g *protogen.GeneratedFile, f *fileInfo, m *messageInfo, field *protogen.Field, goType string, overrideParam overrideParams, overwritten bool) string {
 	if overwritten {
+		log.Log("custom zero value: %q", overrideParam.goZeroOverride)
+		if overrideParam.goZeroOverride != "" {
+			return overrideParam.goZeroOverride
+		}
 		return overwrittenDefault(goType)
 	}
 	if field.Desc.IsList() {
@@ -1051,17 +1069,17 @@ func (c trailingComment) String() string {
 	return s
 }
 
-func goTypeOverride(goType string, msgName string, fieldName string) (string, bool) {
+func goTypeOverride(msgName string, fieldName string) (overrideParams, bool) {
 	if TypeOverride {
 		// TODO check the case when goType is a map
 		if oMsg, okMsg := overrideFields[msgName]; okMsg {
 			if o, okField := oMsg[fieldName]; okField {
-				return o.goType, true
+				return o, true
 			}
 		}
 		// if strings.Contains(goType, "RepeatedString") {
 		// 	return strings.ReplaceAll(goType, "RepeatedString", "[]string")
 		// }
 	}
-	return goType, false
+	return overrideParams{}, false
 }

cmd/protoc-gen-go/internal_gengo/test_data/config.proto

@@ -10,4 +10,5 @@ extend google.protobuf.FieldOptions {
   optional string go_type = 1001;
   optional string go_import = 1002;
   optional string go_import_alias = 1003;
+  optional string go_zero_override = 1004;
 }

cmd/protoc-gen-go/internal_gengo/test_data/test.proto

@@ -29,4 +29,5 @@ message Test {
   string optStr = 4 [(go_type) = "null.String", (go_import) = "github.com/volatiletech/null/v9", (go_import_alias) = "null"];
   int32 optInt = 5 [(go_type) = "null.Int32"];
   int32 optBigInt = 6 [(go_type) = "null.Int64", (go_import) = "github.com/volatiletech/null/v9", (go_import_alias) = "null"];
+  string something = 7 [(go_type) = "Something", (go_import) = "", (go_zero_override) = "\"\""];
 }

internal/impl/decode.go

@@ -20,13 +20,15 @@ import (
 )
 
 const (
-	FieldOptionGoType        = "go_type"
-	FieldOptionGoImport      = "go_import"
-	FieldOptionGoImportAlias = "go_import_alias"
+	FieldOptionGoType         = "go_type"
+	FieldOptionGoImport       = "go_import"
+	FieldOptionGoImportAlias  = "go_import_alias"
+	FieldOptionGoZeroOverride = "go_zero_override"
 
-	FieldOptionGoTypeNum        = 1001
-	FieldOptionGoImportNum      = 1002
-	FieldOptionGoImportAliasNum = 1003
+	FieldOptionGoTypeNum         = 1001
+	FieldOptionGoImportNum       = 1002
+	FieldOptionGoImportAliasNum  = 1003
+	FieldOptionGoZeroOverrideNum = 1004
 )
 
 var errDecode = errors.New("cannot parse invalid wire-format data")
@@ -281,6 +283,8 @@ func (mi *MessageInfo) fallbackCreateExtension(num protowire.Number) (protorefle
 		name = FieldOptionGoImport
 	case FieldOptionGoImportAliasNum:
 		name = FieldOptionGoImportAlias
+	case FieldOptionGoZeroOverrideNum:
+		name = FieldOptionGoZeroOverride
 	default:
 		return nil, errors.New("invalid name")
 	}