feat(html): add cloneable locale and service helpers

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

context.go

@@ -166,6 +166,28 @@ func (ctx *Context) WithIdentity(identity string) *Context {
 	return clone
 }
 
+// WithLocale returns a cloned context with a different locale value.
+// Example: next := ctx.WithLocale("fr-FR").
+func (ctx *Context) WithLocale(locale string) *Context {
+	clone := ctx.Clone()
+	if clone == nil {
+		return nil
+	}
+	clone.SetLocale(locale)
+	return clone
+}
+
+// WithService returns a cloned context with a different translator.
+// Example: next := ctx.WithService(svc).
+func (ctx *Context) WithService(svc Translator) *Context {
+	clone := ctx.Clone()
+	if clone == nil {
+		return nil
+	}
+	clone.SetService(svc)
+	return clone
+}
+
 // SetLocale updates the context locale and reapplies it to the active
 // translator.
 // Example: ctx.SetLocale("en-US").

context_test.go

@@ -202,6 +202,62 @@ func TestContext_WithIdentityReturnsClonedContext(t *testing.T) {
 	}
 }
 
+func TestContext_WithLocaleReturnsClonedContext(t *testing.T) {
+	svc := &localeTranslator{}
+	ctx := NewContextWithService(svc, "en-GB")
+	ctx.SetIdentity("user-001")
+	ctx.SetData("theme", "dark")
+
+	next := ctx.WithLocale("fr-FR")
+
+	if next == ctx {
+		t.Fatal("WithLocale should return a cloned context")
+	}
+	if got := ctx.Locale; got != "en-GB" {
+		t.Fatalf("WithLocale should not mutate the original context locale, got %q", got)
+	}
+	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 svc.language != "fr" {
+		t.Fatalf("WithLocale should reapply locale to the cloned service, got %q", svc.language)
+	}
+	if got := next.Data["theme"]; got != "dark" {
+		t.Fatalf("WithLocale should preserve existing data on the clone, got %v", got)
+	}
+}
+
+func TestContext_WithServiceReturnsClonedContext(t *testing.T) {
+	ctx := NewContext("fr-FR")
+	ctx.SetIdentity("user-001")
+	ctx.SetData("theme", "dark")
+
+	svc := &localeTranslator{}
+	next := ctx.WithService(svc)
+
+	if next == ctx {
+		t.Fatal("WithService should return a cloned context")
+	}
+	if got := ctx.service; got == svc {
+		t.Fatal("WithService should not mutate the original context service")
+	}
+	if got := next.service; got != svc {
+		t.Fatalf("WithService should set the requested service on the clone, got %v", got)
+	}
+	if svc.language != "fr" {
+		t.Fatalf("WithService should apply the existing locale to the new translator, got %q", svc.language)
+	}
+	if got := next.Data["theme"]; got != "dark" {
+		t.Fatalf("WithService should preserve existing data on the clone, got %v", got)
+	}
+	if got := next.Locale; got != "fr-FR" {
+		t.Fatalf("WithService should preserve the locale on the clone, got %q", got)
+	}
+}
+
 func TestContext_Setters_NilReceiver(t *testing.T) {
 	var ctx *Context
 
@@ -217,6 +273,12 @@ func TestContext_Setters_NilReceiver(t *testing.T) {
 	if got := ctx.SetService(&localeTranslator{}); got != nil {
 		t.Fatalf("nil Context.SetService should return nil, got %v", got)
 	}
+	if got := ctx.WithLocale("en-GB"); got != nil {
+		t.Fatalf("nil Context.WithLocale should return nil, got %v", got)
+	}
+	if got := ctx.WithService(&localeTranslator{}); got != nil {
+		t.Fatalf("nil Context.WithService should return nil, got %v", got)
+	}
 }
 
 func TestText_RenderFallsBackToDefaultTranslator(t *testing.T) {