read_pattern() — svelte Function Reference

Source Code

packages/svelte/src/compiler/phases/1-parse/read/context.js lines 12–70

export default function read_pattern(parser) {
	const start = parser.index;
	let i = parser.index;

	const id = parser.read_identifier();

	if (id.name !== '') {
		const annotation = read_type_annotation(parser);

		return {
			...id,
			typeAnnotation: annotation
		};
	}

	const char = parser.template[i];

	if (char !== '{' && char !== '[') {
		e.expected_pattern(i);
	}

	i = match_bracket(parser, start);
	parser.index = i;

	const pattern_string = parser.template.slice(start, i);

	try {
		// the length of the `space_with_newline` has to be start - 1
		// because we added a `(` in front of the pattern_string,
		// which shifted the entire string to right by 1
		// so we offset it by removing 1 character in the `space_with_newline`
		// to achieve that, we remove the 1st space encountered,
		// so it will not affect the `column` of the node
		let space_with_newline = parser.template
			.slice(0, start)
			.replace(regex_not_newline_characters, ' ');
		const first_space = space_with_newline.indexOf(' ');
		space_with_newline =
			space_with_newline.slice(0, first_space) + space_with_newline.slice(first_space + 1);

		const expression = /** @type {any} */ (
			parse_expression_at(
				`${space_with_newline}(${pattern_string} = 1)`,
				parser.root.comments,
				parser.ts,
				start - 1
			)
		).left;

		expression.typeAnnotation = read_type_annotation(parser);
		if (expression.typeAnnotation) {
			expression.end = expression.typeAnnotation.end;
		}

		return expression;
	} catch (error) {
		parser.acorn_error(error);
	}
}