fix: add nil-safe rendering paths

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

layout.go

@@ -111,6 +111,10 @@ func (l *Layout) VariantError() error {
 // Render produces the semantic HTML for this layout.
 // Only slots present in the variant string are rendered.
 func (l *Layout) Render(ctx *Context) string {
+	if l == nil {
+		return ""
+	}
+
 	var b strings.Builder
 
 	for i := range len(l.variant) {

layout_test.go

@@ -211,3 +211,11 @@ func TestLayout_VariantError(t *testing.T) {
 		})
 	}
 }
+
+func TestLayout_RenderNilReceiver(t *testing.T) {
+	var layout *Layout
+	got := layout.Render(NewContext())
+	if got != "" {
+		t.Fatalf("nil Layout should render empty string, got %q", got)
+	}
+}

node.go

@@ -96,6 +96,9 @@ func Raw(content string) Node {
 }
 
 func (n *rawNode) Render(_ *Context) string {
+	if n == nil {
+		return ""
+	}
 	return n.content
 }
 
@@ -156,6 +159,10 @@ func TabIndex(n Node, index int) Node {
 }
 
 func (n *elNode) Render(ctx *Context) string {
+	if n == nil {
+		return ""
+	}
+
 	var b strings.Builder
 
 	b.WriteByte('<')
@@ -210,6 +217,10 @@ func Text(key string, args ...any) Node {
 }
 
 func (n *textNode) Render(ctx *Context) string {
+	if n == nil {
+		return ""
+	}
+
 	var text string
 	if ctx != nil && ctx.service != nil {
 		text = ctx.service.T(n.key, n.args...)
@@ -232,6 +243,10 @@ func If(cond func(*Context) bool, node Node) Node {
 }
 
 func (n *ifNode) Render(ctx *Context) string {
+	if n == nil || n.cond == nil || n.node == nil {
+		return ""
+	}
+
 	if n.cond(ctx) {
 		return n.node.Render(ctx)
 	}
@@ -251,6 +266,10 @@ func Unless(cond func(*Context) bool, node Node) Node {
 }
 
 func (n *unlessNode) Render(ctx *Context) string {
+	if n == nil || n.cond == nil || n.node == nil {
+		return ""
+	}
+
 	if !n.cond(ctx) {
 		return n.node.Render(ctx)
 	}
@@ -271,6 +290,10 @@ func Entitled(feature string, node Node) Node {
 }
 
 func (n *entitledNode) Render(ctx *Context) string {
+	if n == nil || n.node == nil {
+		return ""
+	}
+
 	if ctx == nil || ctx.Entitlements == nil || !ctx.Entitlements(n.feature) {
 		return ""
 	}
@@ -290,6 +313,10 @@ func Switch(selector func(*Context) string, cases map[string]Node) Node {
 }
 
 func (n *switchNode) Render(ctx *Context) string {
+	if n == nil || n.selector == nil || n.cases == nil {
+		return ""
+	}
+
 	key := n.selector(ctx)
 	if node, ok := n.cases[key]; ok {
 		return node.Render(ctx)
@@ -315,6 +342,10 @@ func EachSeq[T any](items iter.Seq[T], fn func(T) Node) Node {
 }
 
 func (n *eachNode[T]) Render(ctx *Context) string {
+	if n == nil || n.items == nil || n.fn == nil {
+		return ""
+	}
+
 	var b strings.Builder
 	for item := range n.items {
 		b.WriteString(n.fn(item).Render(ctx))

pipeline.go

@@ -62,6 +62,9 @@ func CompareVariants(r *Responsive, ctx *Context) map[string]float64 {
 	if ctx == nil {
 		ctx = NewContext()
 	}
+	if r == nil {
+		return map[string]float64{}
+	}
 
 	type named struct {
 		name string

pipeline_test.go

@@ -128,3 +128,10 @@ func TestCompareVariants(t *testing.T) {
 		t.Errorf("same content in different variants should score >= 0.8, got %f", sim)
 	}
 }
+
+func TestCompareVariants_NilResponsive(t *testing.T) {
+	scores := CompareVariants(nil, NewContext())
+	if len(scores) != 0 {
+		t.Fatalf("CompareVariants(nil, ctx) = %v, want empty map", scores)
+	}
+}

render.go

@@ -5,5 +5,8 @@ func Render(node Node, ctx *Context) string {
 	if ctx == nil {
 		ctx = NewContext()
 	}
+	if node == nil {
+		return ""
+	}
 	return node.Render(ctx)
 }

render_test.go

@@ -95,3 +95,10 @@ func TestRender_XSSPrevention(t *testing.T) {
 		t.Errorf("XSS prevention: expected escaped script tag, got:\n%s", got)
 	}
 }
+
+func TestRender_NilNode(t *testing.T) {
+	got := Render(nil, NewContext())
+	if got != "" {
+		t.Fatalf("Render(nil, ctx) = %q, want empty string", got)
+	}
+}

responsive.go

@@ -65,6 +65,10 @@ func (r *Responsive) Variant(name string, layout *Layout) *Responsive {
 
 // Render produces HTML with each variant in a data-variant container.
 func (r *Responsive) Render(ctx *Context) string {
+	if r == nil {
+		return ""
+	}
+
 	var b strings.Builder
 	for _, v := range r.variants {
 		b.WriteString(`<div data-variant="`)

responsive_test.go

@@ -88,6 +88,14 @@ func TestResponsive_ImplementsNode(t *testing.T) {
 	var _ Node = NewResponsive()
 }
 
+func TestResponsive_RenderNilReceiver(t *testing.T) {
+	var r *Responsive
+	got := r.Render(NewContext())
+	if got != "" {
+		t.Fatalf("nil Responsive should render empty string, got %q", got)
+	}
+}
+
 func TestVariantSelector(t *testing.T) {
 	tests := []struct {
 		name    string