build_element_attributes() — svelte Function Reference

Source Code

packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/element.js lines 31–279

export function build_element_attributes(node, context, transform) {
	/** @type {Array<AST.Attribute | AST.SpreadAttribute>} */
	const attributes = [];

	/** @type {AST.ClassDirective[]} */
	const class_directives = [];

	/** @type {AST.StyleDirective[]} */
	const style_directives = [];

	/** @type {Expression | null} */
	let content = null;

	let has_spread = false;
	let events_to_capture = new Set();

	for (const attribute of node.attributes) {
		if (attribute.type === 'Attribute') {
			if (attribute.name === 'value') {
				if (node.name === 'textarea') {
					if (
						attribute.value !== true &&
						Array.isArray(attribute.value) &&
						attribute.value[0].type === 'Text' &&
						regex_starts_with_newline.test(attribute.value[0].data)
					) {
						// Two or more leading newlines are required to restore the leading newline immediately after `<textarea>`.
						// see https://html.spec.whatwg.org/multipage/syntax.html#element-restrictions
						// also see related code in analysis phase
						attribute.value[0].data = '\n' + attribute.value[0].data;
					}

					content = b.call('$.escape', build_attribute_value(attribute.value, context, transform));
				} else if (node.name !== 'select') {
					// omit value attribute for select elements, it's irrelevant for the initially selected value and has no
					// effect on the selected value after the user interacts with the select element (the value _property_ does, but not the attribute)
					attributes.push(attribute);
				}

				// omit event handlers except for special cases
			} else if (is_event_attribute(attribute)) {
				if (
					(attribute.name === 'onload' || attribute.name === 'onerror') &&
					is_load_error_element(node.name)
				) {
					events_to_capture.add(attribute.name);
				}
				// the defaultValue/defaultChecked properties don't exist as attributes
			} else if (attribute.name !== 'defaultValue' && attribute.name !== 'defaultChecked') {
				if (attribute.name === 'class') {
					if (attribute.metadata.needs_clsx) {
						attributes.push({
							...attribute,
							value: {
								.../** @type {AST.ExpressionTag} */ (attribute.value),
								expression: b.call(
									'$.clsx',
									/** @type {AST.ExpressionTag} */ (attribute.value).expression
								)
							}
						});
					} else {
						attributes.push(attribute);
					}
				} else {
					attributes.push(attribute);
				}
			}
		} else if (attribute.type === 'BindDirective') {
			if (attribute.name === 'value' && node.name === 'select') continue;
			if (
				attribute.name === 'value' &&
				attributes.some(
					(attr) =>
						attr.type === 'Attribute' &&
						attr.name === 'type' &&
						is_text_attribute(attr) &&
						attr.value[0].data === 'file'
				)
			) {
				continue;