Function grammar

lib/css/syntax.js:3045–3140

(input, visitors, options)

 * @param {CssProcessOptions} options process options
 */
const grammar = (input, visitors, options) => {
	const { comment } = options;
	const locConverter = options.locConverter || new LocConverter(input);
	useSoaBackend(input, locConverter);
	const recurseBlocks = options.recurseBlocks !== false;

	// Babel's `path.skip()`, children-only. Reset per `enter` dispatch.
	let skipFlag = false;
	const visitorCtx = {
		skipChildren() {
			skipFlag = true;
		}
	};

	/**
	 * Walk a component-value subtree; children are already materialized. Fetches
	 * the node's visitor bucket once (reused for enter + exit) and uses index
	 * loops — `for…of` would allocate an iterator per node on this hot path.
	 * @param {Node} node component-value root
	 * @param {Node | null} parent enclosing node
	 */
	const walkValue = (node, parent) => {
		const ty = _soaTy[_ix(node)];
		const b = visitors[ty];
		let skip = false;
		if (b !== undefined && b.enter.length !== 0) {
			skipFlag = false;
			const e = b.enter;
			for (let i = 0; i < e.length; i++) e[i](node, parent, visitorCtx);
			skip = skipFlag;
			skipFlag = false;
		}
		if (!skip && (ty === T_FUNCTION || ty === T_SIMPLE_BLOCK)) {
			const v = /** @type {Node[]} */ (_soaL0[_ix(node)]);
			for (let i = 0; i < v.length; i++) walkValue(v[i], node);
		}
		if (b !== undefined) {
			const x = b.exit;
			for (let i = 0; i < x.length; i++) x[i](node, parent, visitorCtx);
		}
	};

	/**
	 * Walk a structural subtree; an at-rule / qualified-rule's block was parsed
	 * eagerly (§5.4.4), so its `value` holds the nested rules / declarations.
	 * @param {Node} node structural-tree root
	 * @param {Node | null} parent enclosing node
	 */
	const walkRule = (node, parent) => {
		const i0 = _ix(node);
		const ty = _soaTy[i0];
		const b = visitors[ty];
		let skip = false;
		if (b !== undefined && b.enter.length !== 0) {
			skipFlag = false;
			const e = b.enter;
			for (let i = 0; i < e.length; i++) e[i](node, parent, visitorCtx);
			skip = skipFlag;