AwaitBlock() — svelte Function Reference

Source Code

packages/svelte/src/compiler/phases/3-transform/client/visitors/AwaitBlock.js lines 14–89

export function AwaitBlock(node, context) {
	context.state.template.push_comment();

	// Visit {#await <expression>} first to ensure that scopes are in the correct order
	const expression = b.thunk(
		build_expression(context, node.expression, node.metadata.expression),
		node.metadata.expression.has_await
	);

	let then_block;
	let catch_block;

	if (node.then) {
		const then_context = {
			...context,
			state: { ...context.state, transform: { ...context.state.transform } }
		};
		const argument = node.value && create_derived_block_argument(node.value, then_context);

		/** @type {Pattern[]} */
		const args = [b.id('$$anchor')];
		if (argument) args.push(argument.id);

		const declarations = argument?.declarations ?? [];
		const block = /** @type {BlockStatement} */ (then_context.visit(node.then, then_context.state));

		then_block = b.arrow(args, b.block([...declarations, ...block.body]));
	}

	if (node.catch) {
		const catch_context = { ...context, state: { ...context.state } };
		const argument = node.error && create_derived_block_argument(node.error, catch_context);

		/** @type {Pattern[]} */
		const args = [b.id('$$anchor')];
		if (argument) args.push(argument.id);

		const declarations = argument?.declarations ?? [];
		const block = /** @type {BlockStatement} */ (
			catch_context.visit(node.catch, catch_context.state)
		);

		catch_block = b.arrow(args, b.block([...declarations, ...block.body]));
	}

	const stmt = add_svelte_meta(
		b.call(
			'$.await',
			context.state.node,
			expression,
			node.pending
				? b.arrow([b.id('$$anchor')], /** @type {BlockStatement} */ (context.visit(node.pending)))
				: b.null,
			then_block,
			catch_block
		),
		node,
		'await'
	);

	if (node.metadata.expression.has_blockers()) {
		context.state.init.push(
			b.stmt(
				b.call(
					'$.async',
					context.state.node,
					node.metadata.expression.blockers(),
					b.array([]),
					b.arrow([context.state.node], b.block([stmt]))
				)
			)
		);
	} else {
		context.state.init.push(stmt);
	}
}