svelte/src/compiler/phases/2-analyze/visitors/EachBlock.js

Cybernetically enhanced web apps

/** @import { AST } from '#compiler' */
/** @import { Context } from '../types' */
/** @import { Scope } from '../../scope' */
import * as e from '../../../errors.js';
import { mark_subtree_dynamic } from './shared/fragment.js';
import { validate_block_not_empty, validate_opening_tag } from './shared/utils.js';

/**
 * @param {AST.EachBlock} node
 * @param {Context} context
 */
export function EachBlock(node, context) {
	validate_opening_tag(node, context.state, '#');

	validate_block_not_empty(node.body, context);
	validate_block_not_empty(node.fallback, context);

	const id = node.context;
	if (id?.type === 'Identifier' && (id.name === '$state' || id.name === '$derived')) {
		// TODO weird that this is necessary
		e.state_invalid_placement(node, id.name);
	}

	if (node.key) {
		// treat `{#each items as item, i (i)}` as a normal indexed block, everything else as keyed
		node.metadata.keyed =
			node.key.type !== 'Identifier' || !node.index || node.key.name !== node.index;
	}

	// evaluate expression in parent scope
	context.visit(node.expression, {
		...context.state,
		expression: node.metadata.expression,
		scope: /** @type {Scope} */ (context.state.scope.parent)
	});

	context.visit(node.body);
	if (node.key) context.visit(node.key);
	if (node.fallback) context.visit(node.fallback);

	mark_subtree_dynamic(context.path);
}