fix(html): ignore empty helper tokens

Drop empty strings from join-based accessibility helpers and class names so generated attributes stay clean.

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

node.go

@@ -187,21 +187,30 @@ func AriaLabel(n Node, label string) Node {
 // Example: AriaDescribedBy(El("input"), "help-text", "error-text").
 // Multiple IDs are joined with spaces, matching the HTML attribute format.
 func AriaDescribedBy(n Node, ids ...string) Node {
-	return Attr(n, "aria-describedby", strings.Join(ids, " "))
+	if value := joinNonEmpty(ids...); value != "" {
+		return Attr(n, "aria-describedby", value)
+	}
+	return n
 }
 
 // node.go: AriaLabelledBy sets the aria-labelledby attribute on an element node.
 // Example: AriaLabelledBy(El("section"), "section-title").
 // Multiple IDs are joined with spaces, matching the HTML attribute format.
 func AriaLabelledBy(n Node, ids ...string) Node {
-	return Attr(n, "aria-labelledby", strings.Join(ids, " "))
+	if value := joinNonEmpty(ids...); value != "" {
+		return Attr(n, "aria-labelledby", value)
+	}
+	return n
 }
 
 // node.go: AriaControls sets the aria-controls attribute on an element node.
 // Example: AriaControls(El("button"), "menu-panel").
 // Multiple IDs are joined with spaces, matching the HTML attribute format.
 func AriaControls(n Node, ids ...string) Node {
-	return Attr(n, "aria-controls", strings.Join(ids, " "))
+	if value := joinNonEmpty(ids...); value != "" {
+		return Attr(n, "aria-controls", value)
+	}
+	return n
 }
 
 // node.go: AriaCurrent sets the aria-current attribute on an element node.
@@ -278,7 +287,10 @@ func AltText(n Node, text string) Node {
 // Example: Class(El("div"), "card", "card--primary").
 // Multiple class tokens are joined with spaces.
 func Class(n Node, classes ...string) Node {
-	return Attr(n, "class", strings.Join(classes, " "))
+	if value := joinNonEmpty(classes...); value != "" {
+		return Attr(n, "class", value)
+	}
+	return n
 }
 
 // node.go: AriaHidden sets the aria-hidden attribute on an element node.
@@ -338,6 +350,24 @@ func AutoFocus(n Node) Node {
 	return Attr(n, "autofocus", "autofocus")
 }
 
+func joinNonEmpty(parts ...string) string {
+	if len(parts) == 0 {
+		return ""
+	}
+
+	var filtered []string
+	for i := range parts {
+		if parts[i] == "" {
+			continue
+		}
+		filtered = append(filtered, parts[i])
+	}
+	if len(filtered) == 0 {
+		return ""
+	}
+	return strings.Join(filtered, " ")
+}
+
 func (n *elNode) Render(ctx *Context) string {
 	if n == nil {
 		return ""

node_test.go

@@ -265,6 +265,16 @@ func TestAriaDescribedByHelper(t *testing.T) {
 	}
 }
 
+func TestAriaDescribedByHelper_IgnoresEmptyIDs(t *testing.T) {
+	ctx := NewContext()
+	node := AriaDescribedBy(El("input"), "", "hint-1", "", "hint-2")
+	got := node.Render(ctx)
+	want := `<input aria-describedby="hint-1 hint-2">`
+	if got != want {
+		t.Errorf("AriaDescribedBy() with empty IDs = %q, want %q", got, want)
+	}
+}
+
 func TestAriaLabelledByHelper(t *testing.T) {
 	ctx := NewContext()
 	node := AriaLabelledBy(El("input"), "label-1", "label-2")
@@ -275,6 +285,16 @@ func TestAriaLabelledByHelper(t *testing.T) {
 	}
 }
 
+func TestAriaLabelledByHelper_IgnoresEmptyIDs(t *testing.T) {
+	ctx := NewContext()
+	node := AriaLabelledBy(El("input"), "", "label-1", "", "label-2")
+	got := node.Render(ctx)
+	want := `<input aria-labelledby="label-1 label-2">`
+	if got != want {
+		t.Errorf("AriaLabelledBy() with empty IDs = %q, want %q", got, want)
+	}
+}
+
 func TestAriaControlsHelper(t *testing.T) {
 	ctx := NewContext()
 	node := AriaControls(El("button", Raw("menu")), "menu-panel", "shortcut-hints")
@@ -285,6 +305,16 @@ func TestAriaControlsHelper(t *testing.T) {
 	}
 }
 
+func TestAriaControlsHelper_IgnoresEmptyIDs(t *testing.T) {
+	ctx := NewContext()
+	node := AriaControls(El("button", Raw("menu")), "", "menu-panel", "")
+	got := node.Render(ctx)
+	want := `<button aria-controls="menu-panel">menu</button>`
+	if got != want {
+		t.Errorf("AriaControls() with empty IDs = %q, want %q", got, want)
+	}
+}
+
 func TestAriaCurrentHelper(t *testing.T) {
 	ctx := NewContext()
 	node := AriaCurrent(El("a", Raw("Home")), "page")
@@ -412,6 +442,16 @@ func TestClassHelper(t *testing.T) {
 	}
 }
 
+func TestClassHelper_IgnoresEmptyClasses(t *testing.T) {
+	ctx := NewContext()
+	node := Class(El("div", Raw("content")), "", "card", "", "card--primary")
+	got := node.Render(ctx)
+	want := `<div class="card card--primary">content</div>`
+	if got != want {
+		t.Errorf("Class() with empty classes = %q, want %q", got, want)
+	}
+}
+
 func TestAriaHiddenHelper(t *testing.T) {
 	ctx := NewContext()