css_parse 0.0.24-canary.e4ebbd3fc7

A recursive-descent CSS parser with generic cursor sinks and rich diagnostics.
Documentation 
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/// Aggregated metadata for nodes, that can propagate up a node tree.
pub trait NodeMetadata: Sized + Copy + Default {
	/// Merges another NodeMetadata into this one, returning the result.
	fn merge(self, other: Self) -> Self;

	/// Sets the size of this metadata (e.g., number of declarations, selector list length).
	/// Default implementation is a no-op for metadata types that don't track size.
	fn with_size(self, _size: u16) -> Self {
		self
	}
}

/// A Node that has NodeMetadata
pub trait NodeWithMetadata<M: NodeMetadata> {
	/// Returns the metadata contributed by this node itself, not including children.
	/// Most nodes don't contribute metadata, so can simply return `M::default()`.
	/// Nodes like StyleRule or AtRules should return their own node kind flags here.
	fn self_metadata(&self) -> M {
		M::default()
	}

	/// Returns the complete aggregated metadata for this node (self + children).
	/// Default implementation merges children's metadata with self_metadata().
	fn metadata(&self) -> M;
}

// Stub implementation allowing tests to use () for M
impl NodeMetadata for () {
	fn merge(self, _: Self) -> Self {}
}

// Blanket implementation for Option<T> where T: NodeWithMetadata<M>
// Returns default metadata when None, or delegates to the inner value when Some
impl<M: NodeMetadata, T: NodeWithMetadata<M>> NodeWithMetadata<M> for Option<T> {
	fn self_metadata(&self) -> M {
		match self {
			Some(inner) => inner.self_metadata(),
			None => M::default(),
		}
	}

	fn metadata(&self) -> M {
		match self {
			Some(inner) => inner.metadata(),
			None => M::default(),
		}
	}
}