attr::none

fix #12

CHANGELOG.md

@@ -7,6 +7,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
 
+### Added
+
+* `attr::none()` for conditional rendering of an attribute
+* implement `Default` for `Element` and `Attribute`
+
 
 ## [1.4.0] - 2024-12-13
 

src/attr.rs

@@ -13,6 +13,23 @@ impl<T: Into<Cow<'static, str>>> From<(&'static str, T)> for Attribute {
     }
 }
 
+/// Do not render any attribute. Useful for conditional rendering.
+///
+/// # Example
+///
+/// ```
+/// use fun_html::{attr, elt};
+///
+/// let name: Option<&str> = None;
+/// let element = elt::div([
+///   // Note, `unwrap_or_default()` would have the same effect here
+///   name.map(attr::name).unwrap_or(attr::none()),
+/// ], []);
+/// ```
+pub fn none() -> Attribute {
+    Attribute(crate::AttributeInner::None)
+}
+
 /// `id` attribute
 pub fn id(id: impl Into<Cow<'static, str>>) -> Attribute {
     Attribute::new("id", id)

src/lib.rs

@@ -95,7 +95,7 @@ pub struct Document(Element);
 ///
 /// assert_eq!(element.to_string(), "<div></div>");
 /// ```    
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Default)]
 pub struct Element(ElementInner);
 
 #[derive(Debug, Clone)]
@@ -116,6 +116,12 @@ enum ElementInner {
     None,
 }
 
+impl Default for ElementInner {
+    fn default() -> Self {
+        Self::None
+    }
+}
+
 /// An attribute
 ///
 /// It can be created via [`Self::new`], [`Self::new_flag`]
@@ -132,14 +138,21 @@ enum ElementInner {
 ///   r#"id="foo""#,
 /// )
 /// ```    
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Default)]
 pub struct Attribute(AttributeInner);
 
 #[derive(Debug, Clone)]
 enum AttributeInner {
     KeyValue(Cow<'static, str>, Cow<'static, str>),
     KeyValueInt(Cow<'static, str>, i32),
     Flag(Cow<'static, str>),
+    None,
+}
+
+impl Default for AttributeInner {
+    fn default() -> Self {
+        Self::None
+    }
 }
 
 impl Default for Document {
@@ -237,9 +250,12 @@ impl Display for Element {
 
 fn write_attributes(
     f: &mut alloc::fmt::Formatter<'_>,
-    attributes: &Vec<Attribute>,
+    attributes: &[Attribute],
 ) -> Result<(), alloc::fmt::Error> {
-    for attribute in attributes {
+    for attribute in attributes
+        .iter()
+        .filter(|a| !matches!(&a.0, AttributeInner::None))
+    {
         write!(f, " {attribute}")?;
     }
     Ok(())
@@ -260,6 +276,7 @@ impl Display for Attribute {
                 write!(f, "{key}=\"{value}\"")
             }
             AttributeInner::Flag(key) => write!(f, "{key}"),
+            AttributeInner::None => Ok(()),
         }
     }
 }

tests/render_spec.rs

@@ -29,6 +29,7 @@ fn should_render_html_document() {
 }
 
 #[rstest]
+#[case(attr::none(), "")]
 #[case(("foo", "bar").into(), "foo=\"bar\"")]
 #[case(("x-on:keyup.enter", "doSomething").into(), "x-on:keyup.enter=\"doSomething\"")]
 #[case(("@keyup.enter", "doSomething").into(), "@keyup.enter=\"doSomething\"")]
@@ -98,6 +99,7 @@ fn should_render_attribute(#[case] attr: Attribute, #[case] expected: &str) {
 #[rstest]
 #[case(elt::none(), "")]
 #[case([elt::div([], []), elt::div([], [])].into(), "<div></div><div></div>")]
+#[case(elt::div([attr::none(), attr::none()], []), "<div></div>")]
 #[case(elt::div([], elt::div([], [])), "<div><div></div></div>")]
 #[case(elt::text("hello"), "hello")]
 #[case(elt::text("hello".to_string()), "hello")]