only build map of custom unmarshalers once instead of every call to u…

…nmarshal

decode.go

@@ -35,6 +35,15 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
+var (
+	// We have to initialize this from an init() function below
+	// instead of via initializer expression here to avoid the Go
+	// compiler complaining about a potential initialization cycle
+	// (the initializer expression refers to the function
+	// unmarshalAnyMsg, which indirectly refers back to this var).
+	wktUnmarshalers map[protoreflect.FullName]customUnmarshaler
+)
+
 // Validator is an interface for validating a Protobuf message produced from a given YAML node.
 type Validator interface {
 	// Validate the given message.
@@ -139,13 +148,10 @@ func (o UnmarshalOptions) unmarshalNode(node *yaml.Node, message proto.Message,
 	}
 	unm := &unmarshaler{
 		options:   o,
-		custom:    make(map[protoreflect.FullName]customUnmarshaler),
 		validator: o.Validator,
 		lines:     strings.Split(string(data), "\n"),
 	}
 
-	addWktUnmarshalers(unm.custom)
-
 	// Unwrap the document node
 	if node.Kind == yaml.DocumentNode {
 		if len(node.Content) != 1 {
@@ -188,7 +194,6 @@ type protoResolver interface {
 type unmarshaler struct {
 	options   UnmarshalOptions
 	errors    []error
-	custom    map[protoreflect.FullName]customUnmarshaler
 	validator Validator
 	lines     []string
 }
@@ -657,7 +662,7 @@ func (u *unmarshaler) findNodeForCustom(node *yaml.Node, forAny bool) *yaml.Node
 // Unmarshal the given yaml node into the given proto.Message.
 func (u *unmarshaler) unmarshalMessage(node *yaml.Node, message proto.Message, forAny bool) {
 	// Check for a custom unmarshaler
-	if custom, ok := u.custom[message.ProtoReflect().Descriptor().FullName()]; ok {
+	if custom, ok := wktUnmarshalers[message.ProtoReflect().Descriptor().FullName()]; ok {
 		valueNode := u.findNodeForCustom(node, forAny)
 		if valueNode == nil {
 			return // Error already added.
@@ -718,28 +723,6 @@ func (u *unmarshaler) unmarshalMessageFields(node *yaml.Node, message proto.Mess
 
 type customUnmarshaler func(u *unmarshaler, node *yaml.Node, message proto.Message) bool
 
-// Add all well-known type unmarshalers to the given map (including struct unmarshalers).
-func addWktUnmarshalers(custom map[protoreflect.FullName]customUnmarshaler) {
-	custom["google.protobuf.Any"] = unmarshalAnyMsg
-
-	custom["google.protobuf.Duration"] = unmarshalDurationMsg
-	custom["google.protobuf.Timestamp"] = unmarshalTimestampMsg
-
-	custom["google.protobuf.BoolValue"] = unmarshalWrapperMsg
-	custom["google.protobuf.BytesValue"] = unmarshalWrapperMsg
-	custom["google.protobuf.DoubleValue"] = unmarshalWrapperMsg
-	custom["google.protobuf.FloatValue"] = unmarshalWrapperMsg
-	custom["google.protobuf.Int32Value"] = unmarshalWrapperMsg
-	custom["google.protobuf.Int64Value"] = unmarshalWrapperMsg
-	custom["google.protobuf.UInt32Value"] = unmarshalWrapperMsg
-	custom["google.protobuf.UInt64Value"] = unmarshalWrapperMsg
-	custom["google.protobuf.StringValue"] = unmarshalWrapperMsg
-
-	custom["google.protobuf.Value"] = unmarshalValueMsg
-	custom["google.protobuf.ListValue"] = unmarshalListValueMsg
-	custom["google.protobuf.Struct"] = unmarshalStructMsg
-}
-
 func unmarshalAnyMsg(unm *unmarshaler, node *yaml.Node, message proto.Message) bool {
 	if node.Kind != yaml.MappingNode || len(node.Content) == 0 {
 		return false
@@ -1359,3 +1342,23 @@ func leadingInt(str string) (result uint64, rem string, pre bool, err error) {
 	}
 	return result, str[i:], i > 0, nil
 }
+
+func init() { //nolint:gochecknoinits
+	wktUnmarshalers = map[protoreflect.FullName]customUnmarshaler{
+		"google.protobuf.Any":         unmarshalAnyMsg,
+		"google.protobuf.Duration":    unmarshalDurationMsg,
+		"google.protobuf.Timestamp":   unmarshalTimestampMsg,
+		"google.protobuf.BoolValue":   unmarshalWrapperMsg,
+		"google.protobuf.BytesValue":  unmarshalWrapperMsg,
+		"google.protobuf.DoubleValue": unmarshalWrapperMsg,
+		"google.protobuf.FloatValue":  unmarshalWrapperMsg,
+		"google.protobuf.Int32Value":  unmarshalWrapperMsg,
+		"google.protobuf.Int64Value":  unmarshalWrapperMsg,
+		"google.protobuf.UInt32Value": unmarshalWrapperMsg,
+		"google.protobuf.UInt64Value": unmarshalWrapperMsg,
+		"google.protobuf.StringValue": unmarshalWrapperMsg,
+		"google.protobuf.Value":       unmarshalValueMsg,
+		"google.protobuf.ListValue":   unmarshalListValueMsg,
+		"google.protobuf.Struct":      unmarshalStructMsg,
+	}
+}