fix(html): normalise zero-value context defaults

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

context.go

@@ -33,10 +33,21 @@ func applyLocaleToService(svc Translator, locale string) {
 	}
 }
 
+// ensureContextDefaults initialises lazily-created context fields.
+func ensureContextDefaults(ctx *Context) {
+	if ctx == nil {
+		return
+	}
+	if ctx.Data == nil {
+		ctx.Data = make(map[string]any)
+	}
+}
+
 // normaliseContext ensures render paths always have a usable context.
 // A nil input is replaced with a fresh default context.
 func normaliseContext(ctx *Context) *Context {
 	if ctx != nil {
+		ensureContextDefaults(ctx)
 		return ctx
 	}
 	return NewContext()
@@ -71,6 +82,7 @@ func (ctx *Context) SetService(svc Translator) *Context {
 		return nil
 	}
 
+	ensureContextDefaults(ctx)
 	ctx.service = svc
 	applyLocaleToService(svc, ctx.Locale)
 	return ctx
@@ -83,6 +95,7 @@ func (ctx *Context) SetLocale(locale string) *Context {
 		return nil
 	}
 
+	ensureContextDefaults(ctx)
 	ctx.Locale = locale
 	applyLocaleToService(ctx.service, ctx.Locale)
 	return ctx

node_test.go

@@ -48,6 +48,18 @@ func TestNewContextWithService_Locale(t *testing.T) {
 	}
 }
 
+func TestRender_NormalisesZeroValueContext(t *testing.T) {
+	ctx := &Context{}
+	got := Text("hello").Render(ctx)
+
+	if got != "hello" {
+		t.Fatalf("Text(\"hello\").Render(&Context{}) = %q, want %q", got, "hello")
+	}
+	if ctx.Data == nil {
+		t.Fatal("Render should initialise Data on a zero-value context")
+	}
+}
+
 func TestElNode_Render(t *testing.T) {
 	ctx := NewContext()
 	node := El("div", Raw("content"))