fix(html): make fluent builders nil-safe

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

layout.go

@@ -80,6 +80,9 @@ func ValidateLayoutVariant(variant string) error {
 // layout.go: H appends nodes to the Header slot.
 // Example: NewLayout("HCF").H(Raw("head")).
 func (l *Layout) H(nodes ...Node) *Layout {
+	if l == nil {
+		return nil
+	}
 	l.slots['H'] = append(l.slots['H'], nodes...)
 	return l
 }
@@ -87,6 +90,9 @@ func (l *Layout) H(nodes ...Node) *Layout {
 // layout.go: L appends nodes to the Left aside slot.
 // Example: NewLayout("HLCRF").L(Raw("nav")).
 func (l *Layout) L(nodes ...Node) *Layout {
+	if l == nil {
+		return nil
+	}
 	l.slots['L'] = append(l.slots['L'], nodes...)
 	return l
 }
@@ -94,6 +100,9 @@ func (l *Layout) L(nodes ...Node) *Layout {
 // layout.go: C appends nodes to the Content (main) slot.
 // Example: NewLayout("C").C(Raw("body")).
 func (l *Layout) C(nodes ...Node) *Layout {
+	if l == nil {
+		return nil
+	}
 	l.slots['C'] = append(l.slots['C'], nodes...)
 	return l
 }
@@ -101,6 +110,9 @@ func (l *Layout) C(nodes ...Node) *Layout {
 // layout.go: R appends nodes to the Right aside slot.
 // Example: NewLayout("HLCRF").R(Raw("aside")).
 func (l *Layout) R(nodes ...Node) *Layout {
+	if l == nil {
+		return nil
+	}
 	l.slots['R'] = append(l.slots['R'], nodes...)
 	return l
 }
@@ -108,6 +120,9 @@ func (l *Layout) R(nodes ...Node) *Layout {
 // layout.go: F appends nodes to the Footer slot.
 // Example: NewLayout("HCF").F(Raw("foot")).
 func (l *Layout) F(nodes ...Node) *Layout {
+	if l == nil {
+		return nil
+	}
 	l.slots['F'] = append(l.slots['F'], nodes...)
 	return l
 }

layout_test.go

@@ -250,6 +250,26 @@ func TestLayout_RenderNilReceiver(t *testing.T) {
 	}
 }
 
+func TestLayout_BuilderNilReceiver(t *testing.T) {
+	var layout *Layout
+
+	if got := layout.H(Raw("header")); got != nil {
+		t.Fatalf("nil Layout.H() should return nil, got %v", got)
+	}
+	if got := layout.L(Raw("left")); got != nil {
+		t.Fatalf("nil Layout.L() should return nil, got %v", got)
+	}
+	if got := layout.C(Raw("main")); got != nil {
+		t.Fatalf("nil Layout.C() should return nil, got %v", got)
+	}
+	if got := layout.R(Raw("right")); got != nil {
+		t.Fatalf("nil Layout.R() should return nil, got %v", got)
+	}
+	if got := layout.F(Raw("footer")); got != nil {
+		t.Fatalf("nil Layout.F() should return nil, got %v", got)
+	}
+}
+
 func TestLayout_RenderNilContext(t *testing.T) {
 	layout := NewLayout("C").C(Raw("content"))
 	got := layout.Render(nil)

responsive.go

@@ -100,6 +100,9 @@ func ScopeVariant(name, selector string) string {
 // Example: r.Variant("mobile", NewLayout("C").C(Raw("body"))).
 // Variants render in insertion order.
 func (r *Responsive) Variant(name string, layout *Layout) *Responsive {
+	if r == nil {
+		return nil
+	}
 	r.variants = append(r.variants, responsiveVariant{name: name, layout: layout})
 	return r
 }

responsive_test.go

@@ -96,6 +96,13 @@ func TestResponsive_RenderNilReceiver(t *testing.T) {
 	}
 }
 
+func TestResponsive_BuilderNilReceiver(t *testing.T) {
+	var r *Responsive
+	if got := r.Variant("desktop", NewLayout("C")); got != nil {
+		t.Fatalf("nil Responsive.Variant() should return nil, got %v", got)
+	}
+}
+
 func TestResponsive_RenderNilContext(t *testing.T) {
 	r := NewResponsive().
 		Variant("desktop", NewLayout("C").C(Raw("main")))