fix: don't render a comment node for () attributes in template (closes #4079)

tachys/src/html/element/mod.rs

@@ -709,7 +709,7 @@ where
 
             buf.push('<');
             buf.push_str(E::TAG);
-            <At as ToTemplate>::to_template(
+            <At as ToTemplate>::to_template_attribute(
                 buf,
                 &mut class,
                 &mut style,

tachys/src/view/mod.rs

@@ -437,6 +437,17 @@ pub trait ToTemplate {
         inner_html: &mut String,
         position: &mut Position,
     );
+
+    /// Renders a view type to a template in attribute position.
+    fn to_template_attribute(
+        buf: &mut String,
+        class: &mut String,
+        style: &mut String,
+        inner_html: &mut String,
+        position: &mut Position,
+    ) {
+        Self::to_template(buf, class, style, inner_html, position);
+    }
 }
 
 /// Keeps track of what position the item currently being hydrated is in, relative to its siblings

tachys/src/view/tuples.rs

@@ -103,6 +103,15 @@ impl ToTemplate for () {
     ) {
         buf.push_str("<!>");
     }
+
+    fn to_template_attribute(
+        _buf: &mut String,
+        _class: &mut String,
+        _style: &mut String,
+        _inner_html: &mut String,
+        _position: &mut Position,
+    ) {
+    }
 }
 
 impl<A: Render> Render for (A,) {