Function consumeADeclaration

lib/css/syntax.js:2607–2686

(ts, nested = false)

 * @returns {Declaration | undefined} parsed declaration, or `undefined` on the spec's "return nothing" branches (steps 1, 3, 8)
 */
const consumeADeclaration = (ts, nested = false) => {
	const { input } = ts;
	// Let decl be a new declaration, with an initially empty name and a value set to an empty list.
	const start = ts.next().start;
	// name "" / nameStart / nameEnd (= start) / important (false) keep their
	// `Container` defaults; `value` is set unconditionally at step 5 below.
	const decl = /** @type {Declaration} */ (
		_mkContainer(T_DECLARATION, start, start)
	);

	// 1. If the next token is an <ident-token>, consume a token from input and set decl's name to the returned token's value.
	// Otherwise, consume the remnants of a bad declaration from input, with nested, and return nothing.
	if (ts.next().type === TT_IDENTIFIER) {
		const head = ts.consume();
		_setName(decl, input.slice(head.start, head.end), head.start, head.end);
	} else {
		consumeTheRemnantsOfABadDeclaration(ts, nested);
		return undefined;
	}

	// 2. Discard whitespace from input.
	while (ts.next().type === TT_WHITESPACE) ts.discard();

	// 3. If the next token is a <colon-token>, discard a token from input.
	//    Otherwise, consume the remnants of a bad declaration from input, with nested, and return nothing.
	if (ts.next().type === TT_COLON) {
		ts.discard();
	} else {
		consumeTheRemnantsOfABadDeclaration(ts, nested);
		return undefined;
	}

	// 4. Discard whitespace from input.
	while (ts.next().type === TT_WHITESPACE) ts.discard();

	// 5. Consume a list of component values from input, with nested, and with <semicolon-token> as the stop token, and set decl's value to the result.
	const value = consumeAListOfComponentValues(ts, TT_SEMICOLON, nested);
	_setValue(decl, value);
	_setEnd(decl, ts.next().start);

	// 6. If the last two non-<whitespace-token>s in decl's value are a <delim-token> with the value "!" followed by an <ident-token> with a value that is an ASCII case-insensitive match for "important", remove them from decl's value and set decl's important flag.
	{
		let last = value.length - 1;
		while (last >= 0 && _nType(value[last]) === T_WHITESPACE) last--;
		let prev = last - 1;
		while (prev >= 0 && _nType(value[prev]) === T_WHITESPACE) prev--;
		if (
			prev >= 0 &&
			_nType(value[last]) === T_IDENT &&
			equalsLowerCase(_nValue(value[last]), "important") &&
			_nType(value[prev]) === T_DELIM &&
			input.charCodeAt(_nStart(value[prev])) === CC_EXCLAMATION
		) {
			_setImportant(decl);
			value.length = prev;
		}
	}