special() — svelte Function Reference

Source Code

packages/svelte/src/compiler/phases/1-parse/state/tag.js lines 616–751

function special(parser) {
	let start = parser.index;
	while (parser.template[start] !== '{') start -= 1;

	if (parser.eat('html')) {
		// {@html content} tag
		parser.require_whitespace();

		const expression = read_expression(parser);

		parser.allow_whitespace();
		parser.eat('}', true);

		parser.append({
			type: 'HtmlTag',
			start,
			end: parser.index,
			expression,
			metadata: {
				expression: new ExpressionMetadata()
			}
		});

		return;
	}

	if (parser.eat('debug')) {
		/** @type {Identifier[]} */
		let identifiers;

		// Implies {@debug} which indicates "debug all"
		if (parser.read(regex_whitespace_with_closing_curly_brace)) {
			identifiers = [];
		} else {
			const expression = read_expression(parser);

			identifiers =
				expression.type === 'SequenceExpression'
					? /** @type {Identifier[]} */ (expression.expressions)
					: [/** @type {Identifier} */ (expression)];

			identifiers.forEach(
				/** @param {any} node */ (node) => {
					if (node.type !== 'Identifier') {
						e.debug_tag_invalid_arguments(/** @type {number} */ (node.start));
					}
				}
			);

			parser.allow_whitespace();
			parser.eat('}', true);
		}

		parser.append({
			type: 'DebugTag',
			start,
			end: parser.index,
			identifiers
		});

		return;
	}

	if (parser.eat('const')) {
		parser.require_whitespace();

		const id = read_pattern(parser);
		parser.allow_whitespace();

		parser.eat('=', true);
		parser.allow_whitespace();

		const expression_start = parser.index;
		const init = read_expression(parser);
		if (
			init.type === 'SequenceExpression' &&
			!parser.template.substring(expression_start, init.start).includes('(')
		) {
			// const a = (b, c) is allowed but a = b, c = d is not;
			e.const_tag_invalid_expression(init);
		}