dyn: Modify FieldValues to return ordered fields (#3327)

The fields have natural order, existing API destroys it by returning
map.

This PR changes FieldValues() to return a more appropriate data
structure. Needed for / extracted from #3230

Author: denik

libs/dyn/convert/from_typed.go

@@ -102,7 +102,9 @@ func fromTypedStruct(src reflect.Value, ref dyn.Value, options ...fromTypedOptio
 	refm, _ := ref.AsMap()
 	out := dyn.NewMapping()
 	info := getStructInfo(src.Type())
-	for k, v := range info.FieldValues(src) {
+	for _, fieldval := range info.FieldValues(src) {
+		k := fieldval.Key
+		v := fieldval.Value
 		pair, ok := refm.GetPairByString(k)
 		refloc := pair.Key.Locations()
 		refv := pair.Value

libs/dyn/convert/struct_info.go

@@ -11,6 +11,9 @@ import (
 // structInfo holds the type information we need to efficiently
 // convert data from a [dyn.Value] to a Go struct.
 type structInfo struct {
+	// FieldNames is ordered list of fields
+	FieldNames []string
+
 	// Fields maps the JSON-name of the field to the field's index for use with [FieldByIndex].
 	Fields map[string][]int
 
@@ -94,17 +97,24 @@ func buildStructInfo(typ reflect.Type) structInfo {
 				continue
 			}
 
+			out.FieldNames = append(out.FieldNames, name)
 			out.Fields[name] = append(prefix, sf.Index...)
 		}
 	}
 
 	return out
 }
 
-func (s *structInfo) FieldValues(v reflect.Value) map[string]reflect.Value {
-	out := make(map[string]reflect.Value)
+type FieldValue struct {
+	Key   string
+	Value reflect.Value
+}
+
+func (s *structInfo) FieldValues(v reflect.Value) []FieldValue {
+	out := make([]FieldValue, 0, len(s.Fields))
 
-	for k, index := range s.Fields {
+	for _, k := range s.FieldNames {
+		index := s.Fields[k]
 		fv := v
 
 		// Locate value in struct (it could be an embedded type).
@@ -122,7 +132,7 @@ func (s *structInfo) FieldValues(v reflect.Value) map[string]reflect.Value {
 		}
 
 		if fv.IsValid() {
-			out[k] = fv
+			out = append(out, FieldValue{Key: k, Value: fv})
 		}
 	}
 

libs/dyn/convert/struct_info_test.go

@@ -103,8 +103,10 @@ func TestStructInfoFieldValues(t *testing.T) {
 	si := getStructInfo(reflect.TypeOf(Tmp{}))
 	fv := si.FieldValues(reflect.ValueOf(src))
 	assert.Len(t, fv, 2)
-	assert.Equal(t, "foo", fv["foo"].String())
-	assert.Equal(t, "bar", fv["bar"].String())
+	assert.Equal(t, "foo", fv[0].Key)
+	assert.True(t, reflect.ValueOf("foo").Equal(fv[0].Value))
+	assert.Equal(t, "bar", fv[1].Key)
+	assert.True(t, reflect.ValueOf("bar").Equal(fv[1].Value))
 }
 
 func TestStructInfoFieldValuesAnonymousByValue(t *testing.T) {
@@ -133,8 +135,8 @@ func TestStructInfoFieldValuesAnonymousByValue(t *testing.T) {
 	si := getStructInfo(reflect.TypeOf(Tmp{}))
 	fv := si.FieldValues(reflect.ValueOf(src))
 	assert.Len(t, fv, 2)
-	assert.Equal(t, "foo", fv["foo"].String())
-	assert.Equal(t, "bar", fv["bar"].String())
+	assert.Equal(t, "foo", fv[0].Key)
+	assert.Equal(t, "bar", fv[1].Key)
 }
 
 func TestStructInfoFieldValuesAnonymousByPointer(t *testing.T) {
@@ -165,8 +167,8 @@ func TestStructInfoFieldValuesAnonymousByPointer(t *testing.T) {
 		si := getStructInfo(reflect.TypeOf(Tmp{}))
 		fv := si.FieldValues(reflect.ValueOf(src))
 		assert.Len(t, fv, 2)
-		assert.Equal(t, "foo", fv["foo"].String())
-		assert.Equal(t, "bar", fv["bar"].String())
+		assert.Equal(t, "foo", fv[0].Key)
+		assert.Equal(t, "bar", fv[1].Key)
 	})
 
 	// Test that fields of embedded types are skipped if the embedded type is nil.
@@ -181,7 +183,7 @@ func TestStructInfoFieldValuesAnonymousByPointer(t *testing.T) {
 		si := getStructInfo(reflect.TypeOf(Tmp{}))
 		fv := si.FieldValues(reflect.ValueOf(src))
 		assert.Len(t, fv, 1)
-		assert.Equal(t, "foo", fv["foo"].String())
+		assert.Equal(t, "foo", fv[0].Key)
 	})
 
 	// Test that fields of embedded types are skipped if the embedded type is nil.