add casttype support for repeated scalar fields

patch/casttype.go

@@ -22,18 +22,41 @@ func (p *Patcher) patchTypeDef(id *ast.Ident, obj types.Object) {
 		astutil.AddNamedImport(p.fset, f, pkgImport, pkg)
 		castType = pkgImport + "." + name
 	}
+
+	castDecl := func(v *ast.Field) bool {
+		switch t := v.Type.(type){
+		case *ast.Ident:
+			t.Name = castType
+			return true
+		case *ast.ArrayType:
+			if strings.HasPrefix(castType, "[]") {
+				if id, ok := t.Elt.(*ast.Ident); ok {
+					id.Name = strings.TrimPrefix(castType, "[]")
+					return true
+				}
+			} else {
+				v.Type = &ast.Ident{
+					Name: castType,
+				}
+				return true
+			}
+		default:
+			return false
+		}
+		return false
+	}
+
 	// Cast Field definition
 	if id.Obj != nil && id.Obj.Decl != nil {
 		v, ok := id.Obj.Decl.(*ast.Field)
 		if !ok {
 			log.Printf("Warning: casttype declared for non-field object: %v `%s`", obj, castType)
 			return
 		}
-		t, ok := v.Type.(*ast.Ident)
-		if ok {
-			t.Name = castType
-			return
+		if !castDecl(v) {
+			log.Printf("Warning: unsupported casttype type: %T `%s`", v.Type, castType)
 		}
+		return
 	}
 	switch obj.Type().(type) {
 	// Cast Getter signature
@@ -47,10 +70,10 @@ func (p *Patcher) patchTypeDef(id *ast.Ident, obj types.Object) {
 			log.Printf("Warning: unexpected return count for getter: %v `%d`", obj, l)
 			return
 		}
-		if ident, ok := n.Type.Results.List[0].Type.(*ast.Ident); ok {
-			ident.Name = castType
-			return
+		if !castDecl(n.Type.Results.List[0]) {
+			log.Printf("Warning: unsupported casttype type: %T `%s`", n.Type.Results.List[0].Type, castType)
 		}
+		return
 	}
 }
 

patch/go.proto

@@ -24,7 +24,7 @@ message Options {
 	// The casstype option changes the generated field type.
 	// All generated code assumes that this type is castable to the protocol buffer field type,
 	// so it does not work for messages types.
-	// Not supported for repeated fields.
+	// Rrepeated fields are also supported, both as '[]Type' or 'Types' where Types is a named slice type.
 	optional string casttype = 3;
 
 	// The getter option renames the generated getter method (default: Get<Field>)

patch/patcher.go

@@ -319,8 +319,6 @@ func (p *Patcher) scanField(f *protogen.Field) {
 	// check casttype
 	if typ := opts.GetCasttype(); typ != "" {
 		switch {
-		case f.Desc.IsList():
-			log.Printf("Warning: casttype declared for repeated field: %s", f.Desc.Name())
 		case f.Message != nil:
 			log.Printf("Warning: casttype declared for message field: %s", f.Desc.Name())
 		case f.Oneof != nil:

tests/message/message.extensions.go

@@ -1,6 +1,7 @@
 package message
 
 type Name string
+type Names []string
 
 type Int32 int32
 
@@ -15,3 +16,5 @@ type Double float64
 type Uint32 uint32
 
 type Uint64 uint64
+
+type Strings []string

tests/message/message_casttypes.proto

@@ -6,8 +6,6 @@ import "patch/go.proto";
 
 option go_package = "github.com/alta/protopatch/tests/message";
 
-
-
 message MessageWithCustomTypes {
   string string_field = 1 [(go.field).casttype = "String"];
   int32 int32_field = 2 [(go.field).casttype = "Int32"];
@@ -24,3 +22,11 @@ message MessageWithOneOfCustomType {
     int64 int64_field = 3 [(go.field).casttype = "Int64"];
   }
 }
+
+message MessageWithCustomRepeatedTypes {
+  repeated string repeated_string_field = 1 [(go.field).casttype = "[]String"];
+}
+
+message MessageWithRepeatedCustomTypes {
+  repeated string repeated_string_field = 1 [(go.field).casttype = "Strings"];
+}

tests/message/message_test.go

@@ -138,3 +138,23 @@ func TestMessageWithCustomTypes(t *testing.T) {
 	assert.Equal(t, Uint32(42), m.Uint32Field)
 	assert.Equal(t, Uint64(42), m.Uint64Field)
 }
+
+func TestMessageWithCustomRepeatedTypes(t *testing.T) {
+	slice := []String{"one", "two"}
+	m := &MessageWithCustomRepeatedTypes{
+		RepeatedStringField: slice,
+	}
+	tests.ValidateMessage(t, m)
+	var _ []String = m.RepeatedStringField
+	assert.Equal(t, slice, m.RepeatedStringField)
+}
+
+func TestMessageWithRepeatedCustomTypes(t *testing.T) {
+	slice := Strings{"one", "two"}
+	m := &MessageWithRepeatedCustomTypes{
+		RepeatedStringField: slice,
+	}
+	tests.ValidateMessage(t, m)
+	var _ Strings = m.RepeatedStringField
+	assert.Equal(t, slice, m.RepeatedStringField)
+}