visit_component() — svelte Function Reference

Source Code

packages/svelte/src/compiler/phases/2-analyze/visitors/shared/component.js lines 19–162

export function visit_component(node, context) {
	node.metadata.path = [...context.path];

	// link this node to all the snippets that it could render, so that we can prune CSS correctly
	node.metadata.snippets = new Set();

	// 'resolved' means we know which snippets this component might render. if it is `false`,
	// then `node.metadata.snippets` is populated with every locally defined snippet
	// once analysis is complete
	let resolved = true;

	for (const attribute of node.attributes) {
		if (attribute.type === 'SpreadAttribute' || attribute.type === 'BindDirective') {
			resolved = false;
			continue;
		}

		if (attribute.type !== 'Attribute' || !is_expression_attribute(attribute)) {
			continue;
		}

		const expression = get_attribute_expression(attribute);

		// given an attribute like `foo={bar}`, if `bar` resolves to an import or a prop
		// then we know it doesn't reference a locally defined snippet. if it resolves
		// to a `{#snippet bar()}` then we know _which_ snippet it resolves to. in all
		// other cases, we can't know (without much more complex static analysis) which
		// snippets the component might render, so we treat the component as unresolved
		if (expression.type === 'Identifier') {
			const binding = context.state.scope.get(expression.name);

			resolved &&= is_resolved_snippet(binding);

			if (binding?.initial?.type === 'SnippetBlock') {
				node.metadata.snippets.add(binding.initial);
			}
		} else if (expression.type !== 'Literal') {
			resolved = false;
		}
	}

	if (resolved) {
		for (const child of node.fragment.nodes) {
			if (child.type === 'SnippetBlock') {
				node.metadata.snippets.add(child);
			}
		}
	}

	context.state.analysis.snippet_renderers.set(node, resolved);

	mark_subtree_dynamic(context.path);

	for (const attribute of node.attributes) {
		if (
			attribute.type !== 'Attribute' &&
			attribute.type !== 'SpreadAttribute' &&
			attribute.type !== 'LetDirective' &&
			attribute.type !== 'OnDirective' &&
			attribute.type !== 'BindDirective' &&
			attribute.type !== 'AttachTag'
		) {
			e.component_invalid_directive(attribute);
		}

		if (
			attribute.type === 'OnDirective' &&
			(attribute.modifiers.length > 1 || attribute.modifiers.some((m) => m !== 'once'))
		) {
			e.event_handler_invalid_component_modifier(attribute);
		}

		if (attribute.type === 'Attribute') {
			if (context.state.analysis.runes) {
				validate_attribute(attribute, node);

				if (is_expression_attribute(attribute)) {
					disallow_unparenthesized_sequences(
						get_attribute_expression(attribute),
						context.state.analysis.source
					);