fix(html): clone mutable translators in context copies

Co-Authored-By: Virgil <virgil@lethean.io>

context.go

@@ -10,6 +10,10 @@ type Translator interface {
 	T(key string, args ...any) string
 }
 
+type translatorCloner interface {
+	Clone() Translator
+}
+
 // context.go: Context carries rendering state through the node tree.
 // Example: NewContext("en-GB") initialises locale-specific rendering state.
 // Locale and translator selection happen at construction time.

context_test.go

@@ -28,6 +28,15 @@ func (t *localeTranslator) SetLanguage(language string) error {
 	return nil
 }
 
+func (t *localeTranslator) Clone() Translator {
+	if t == nil {
+		return (*localeTranslator)(nil)
+	}
+
+	clone := *t
+	return &clone
+}
+
 func TestContext_NewContextWithService_AppliesLocale(t *testing.T) {
 	svc := &localeTranslator{}
 	ctx := NewContextWithService(svc, "fr-FR")
@@ -159,8 +168,8 @@ func TestContext_CloneCopiesDataWithoutSharingMap(t *testing.T) {
 	if clone == ctx {
 		t.Fatal("Clone should return a distinct context instance")
 	}
-	if clone.service != ctx.service {
-		t.Fatal("Clone should preserve the active translator")
+	if clone.service == ctx.service {
+		t.Fatal("Clone should duplicate cloneable translators")
 	}
 	if clone.Locale != ctx.Locale {
 		t.Fatalf("Clone should preserve locale, got %q want %q", clone.Locale, ctx.Locale)
@@ -193,6 +202,31 @@ func TestContext_CloneDoesNotShareDefaultTranslator(t *testing.T) {
 	}
 }
 
+func TestContext_CloneClonesMutableTranslator(t *testing.T) {
+	svc := &localeTranslator{}
+	ctx := NewContextWithService(svc, "en-GB")
+
+	clone := ctx.Clone()
+	if clone == nil {
+		t.Fatal("Clone should return a context")
+	}
+	if clone.service == ctx.service {
+		t.Fatal("Clone should isolate cloneable translators")
+	}
+
+	clone.SetLocale("fr-FR")
+
+	if got := svc.language; got != "en" {
+		t.Fatalf("Clone should not mutate the original translator, got %q", got)
+	}
+	if got := Text("prompt.yes").Render(ctx); got != "y" {
+		t.Fatalf("Clone should leave original context translation unchanged, got %q", got)
+	}
+	if got := Text("prompt.yes").Render(clone); got != "o" {
+		t.Fatalf("Clone should reapply locale to the cloned translator, got %q", got)
+	}
+}
+
 func TestContext_WithDataReturnsClonedContext(t *testing.T) {
 	ctx := NewContext()
 	ctx.SetData("theme", "dark")
@@ -251,11 +285,14 @@ func TestContext_WithLocaleReturnsClonedContext(t *testing.T) {
 	if got := next.Locale; got != "fr-FR" {
 		t.Fatalf("WithLocale should set the requested locale on the clone, got %q", got)
 	}
-	if got := next.service; got != ctx.service {
-		t.Fatal("WithLocale should preserve the active translator on the clone")
+	if got := next.service; got == ctx.service {
+		t.Fatal("WithLocale should duplicate cloneable translators on the clone")
 	}
-	if svc.language != "fr" {
-		t.Fatalf("WithLocale should reapply locale to the cloned service, got %q", svc.language)
+	if svc.language != "en" {
+		t.Fatalf("WithLocale should not mutate the original translator, got %q", svc.language)
+	}
+	if got := Text("prompt.yes").Render(next); got != "o" {
+		t.Fatalf("WithLocale should reapply locale to the cloned service, got %q", got)
 	}
 	if got := next.Data["theme"]; got != "dark" {
 		t.Fatalf("WithLocale should preserve existing data on the clone, got %v", got)

default_translator_js.go

@@ -32,6 +32,15 @@ func (t *defaultTranslator) SetLanguage(language string) error {
 	return nil
 }
 
+func (t *defaultTranslator) Clone() Translator {
+	if t == nil {
+		return (*defaultTranslator)(nil)
+	}
+
+	clone := *t
+	return &clone
+}
+
 func newDefaultTranslator() Translator {
 	return &defaultTranslator{}
 }

go.sum

@@ -14,12 +14,8 @@ github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH
 github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
 github.com/rogpeppe/go-internal v1.14.1 h1:UQB4HGPB6osV0SQTLymcB4TgvyWu6ZyliaW0tI/otEQ=
 github.com/rogpeppe/go-internal v1.14.1/go.mod h1:MaRKkUm5W0goXpeCfT7UZI6fk/L7L7so1lCWt35ZSgc=
-github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
-golang.org/x/mod v0.21.0/go.mod h1:6SkKJ3Xj0I0BrPOZoBy3bdMptDDU9oJrpohJ3eWZ1fY=
-golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/tools v0.26.0/go.mod h1:TPVVj70c7JJ3WCazhD8OdXcZg/og+b9+tH/KxylGwH0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=

translator_clone_default.go

@@ -11,6 +11,12 @@ func cloneTranslator(svc Translator, locale string) Translator {
 		return nil
 	}
 
+	if cloner, ok := svc.(translatorCloner); ok && cloner != nil {
+		if clone := cloner.Clone(); clone != nil {
+			return clone
+		}
+	}
+
 	if current, ok := svc.(*i18n.Service); ok && current != nil {
 		clone := &i18n.Service{}
 		applyLocaleToService(clone, locale)

translator_clone_js.go

@@ -9,6 +9,12 @@ func cloneTranslator(svc Translator, _ string) Translator {
 		return nil
 	}
 
+	if cloner, ok := svc.(translatorCloner); ok && cloner != nil {
+		if clone := cloner.Clone(); clone != nil {
+			return clone
+		}
+	}
+
 	if current, ok := svc.(*defaultTranslator); ok && current != nil {
 		clone := *current
 		return &clone