structs: use only a struct's own ForceSendFields in structdiff and structwalk

libs/structs/structdiff/diff.go

@@ -356,8 +356,14 @@ func getForceSendFields(v reflect.Value) []string {
 	if !v.IsValid() || v.Kind() != reflect.Struct {
 		return nil
 	}
-	fsField := v.FieldByName("ForceSendFields")
-	if !fsField.IsValid() || fsField.Kind() != reflect.Slice {
+	// Only the struct's own ForceSendFields: one promoted from an embedded struct names that
+	// struct's fields, since the SDK marshaller rejects names its struct does not have.
+	sf, ok := v.Type().FieldByName("ForceSendFields")
+	if !ok || len(sf.Index) != 1 {
+		return nil
+	}
+	fsField := v.Field(sf.Index[0])
+	if fsField.Kind() != reflect.Slice {
 		return nil
 	}
 	result, ok := reflect.TypeAssert[[]string](fsField)

libs/structs/structdiff/diff_test.go

@@ -1125,3 +1125,31 @@ func TestGetStructDiffPathsSharingPrefix(t *testing.T) {
 	assert.Equal(t, Change{Path: changes[2].Path, Old: nil, New: "2"}, changes[2])
 	assert.Equal(t, Change{Path: changes[3].Path, Old: "1", New: nil}, changes[3])
 }
+
+type PromotedInner struct {
+	A               string   `json:"a,omitempty"`
+	ForceSendFields []string `json:"-"`
+}
+
+type promotedOuter struct {
+	PromotedInner
+	Own string `json:"own,omitempty"`
+}
+
+// The embedded struct's ForceSendFields does not force the outer struct's own fields;
+// the SDK marshaller would reject a name its struct does not have.
+func TestGetStructDiffEmbeddedForceSendFieldsDoNotApplyToOuterFields(t *testing.T) {
+	forced := promotedOuter{ForceSendFields: []string{"A", "Own"}}
+	plain := promotedOuter{}
+
+	changes, err := GetStructDiff(forced, plain, nil)
+	require.NoError(t, err)
+	assert.Equal(t, []ResolvedChange{{Field: "a", Old: "", New: nil}}, resolveChanges(changes))
+	assert.False(t, IsEqual(forced, plain))
+
+	forced.ForceSendFields = []string{"Own"}
+	changes, err = GetStructDiff(forced, plain, nil)
+	require.NoError(t, err)
+	assert.Empty(t, changes)
+	assert.True(t, IsEqual(forced, plain))
+}

libs/structs/structwalk/walk.go

@@ -155,8 +155,14 @@ func getForceSendFields(v reflect.Value) []string {
 	if !v.IsValid() || v.Kind() != reflect.Struct {
 		return nil
 	}
-	fsField := v.FieldByName("ForceSendFields")
-	if !fsField.IsValid() || fsField.Kind() != reflect.Slice {
+	// Only the struct's own ForceSendFields: one promoted from an embedded struct names that
+	// struct's fields, since the SDK marshaller rejects names its struct does not have.
+	sf, ok := v.Type().FieldByName("ForceSendFields")
+	if !ok || len(sf.Index) != 1 {
+		return nil
+	}
+	fsField := v.Field(sf.Index[0])
+	if fsField.Kind() != reflect.Slice {
 		return nil
 	}
 	result, ok := reflect.TypeAssert[[]string](fsField)

libs/structs/structwalk/walk_test.go

@@ -320,3 +320,20 @@ func walkPaths(t *testing.T, value any) []string {
 	slices.Sort(paths)
 	return paths
 }
+
+type PromotedInner struct {
+	A               string   `json:"a,omitempty"`
+	ForceSendFields []string `json:"-"`
+}
+
+type promotedOuter struct {
+	PromotedInner
+	Own string `json:"own,omitempty"`
+}
+
+// The embedded struct's ForceSendFields does not force the outer struct's own fields;
+// the SDK marshaller would reject a name its struct does not have.
+func TestEmbeddedForceSendFieldsDoNotApplyToOuterFields(t *testing.T) {
+	v := promotedOuter{ForceSendFields: []string{"A", "Own"}}
+	assert.Equal(t, map[string]any{"a": ""}, flatten(t, v))
+}