ExpressionMetadata Class — svelte Architecture

Source Code

packages/svelte/src/compiler/phases/nodes.js lines 70–152

export class ExpressionMetadata {
	/** True if the expression references state directly, or _might_ (via member/call expressions) */
	has_state = false;

	/** True if the expression involves a call expression (often, it will need to be wrapped in a derived) */
	has_call = false;

	/** True if the expression contains `await` */
	has_await = false;

	/** True if the expression includes a member expression */
	has_member_expression = false;

	/** True if the expression includes an assignment or an update */
	has_assignment = false;

	/**
	 * All the bindings that are referenced eagerly (not inside functions) in this expression
	 * @type {Set<Binding>}
	 */
	dependencies = new Set();

	/**
	 * True if the expression references state directly, or _might_ (via member/call expressions)
	 * @type {Set<Binding>}
	 */
	references = new Set();

	/** @type {null | Set<Expression>} */
	#blockers = null;

	#get_blockers() {
		if (!this.#blockers) {
			this.#blockers = new Set();

			for (const d of this.dependencies) {
				if (d.blocker) this.#blockers.add(d.blocker);
			}
		}

		return this.#blockers;
	}

	blockers() {
		return b.array([...this.#get_blockers()]);
	}

	has_blockers() {
		return this.#get_blockers().size > 0;
	}

	/**
	 * @param {ExpressionMetadata} other
	 */
	has_more_blockers_than(other) {
		for (const blocker of this.#get_blockers()) {
			if (!other.#get_blockers().has(blocker)) {
				return true;
			}
		}

		return false;
	}

	is_async() {
		return this.has_await || this.#get_blockers().size > 0;
	}

	/**
	 * @param {ExpressionMetadata} source
	 */
	merge(source) {
		this.has_state ||= source.has_state;
		this.has_call ||= source.has_call;
		this.has_await ||= source.has_await;
		this.has_member_expression ||= source.has_member_expression;
		this.has_assignment ||= source.has_assignment;
		this.#blockers = null; // so that blockers are recalculated

		for (const r of source.references) this.references.add(r);
		for (const b of source.dependencies) this.dependencies.add(b);