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/** @import { Attribute, DelegatedEvent, RegularElement } from '#compiler' */
/** @import { Context } from '../types' */
import { is_capture_event, is_delegated } from '../../../../utils.js';
import {
get_attribute_chunks,
get_attribute_expression,
is_event_attribute
} from '../../../utils/ast.js';
/**
* @param {Attribute} node
* @param {Context} context
*/
export function Attribute(node, context) {
context.next();
if (node.value !== true) {
for (const chunk of get_attribute_chunks(node.value)) {
if (chunk.type !== 'ExpressionTag') continue;
if (
chunk.expression.type === 'FunctionExpression' ||
chunk.expression.type === 'ArrowFunctionExpression'
) {
continue;
}
node.metadata.expression.has_state ||= chunk.metadata.expression.has_state;
node.metadata.expression.has_call ||= chunk.metadata.expression.has_call;
}
if (is_event_attribute(node)) {
const parent = context.path.at(-1);
if (parent?.type === 'RegularElement' || parent?.type === 'SvelteElement') {
context.state.analysis.uses_event_attributes = true;
}
const expression = get_attribute_expression(node);
const delegated_event = get_delegated_event(node.name.slice(2), expression, context);
if (delegated_event !== null) {
if (delegated_event.type === 'hoistable') {
delegated_event.function.metadata.hoistable = true;
}
node.metadata.delegated = delegated_event;
}
}
}
}
/**
* Checks if given event attribute can be delegated/hoisted and returns the corresponding info if so
* @param {string} event_name
* @param {Expression | null} handler
* @param {Context} context
* @returns {null | DelegatedEvent}
*/
function get_delegated_event(event_name, handler, context) {
// Handle delegated event handlers. Bail-out if not a delegated event.
if (!handler || !is_delegated(event_name)) {
return null;
}
// If we are not working with a RegularElement, then bail-out.
const element = context.path.at(-1);
if (element?.type !== 'RegularElement') {
return null;
}
/** @type {DelegatedEvent} */
const non_hoistable = { type: 'non-hoistable' };
/** @type {FunctionExpression | FunctionDeclaration | ArrowFunctionExpression | null} */
let target_function = null;
let binding = null;
if (element.metadata.has_spread) {
// event attribute becomes part of the dynamic spread array
return non_hoistable;
}
if (handler.type === 'ArrowFunctionExpression' || handler.type === 'FunctionExpression') {
target_function = handler;
} else if (handler.type === 'Identifier') {
binding = context.state.scope.get(handler.name);
if (context.state.analysis.module.scope.references.has(handler.name)) {
// If a binding with the same name is referenced in the module scope (even if not declared there), bail-out
return non_hoistable;
}
if (binding != null) {
for (const { path } of binding.references) {
const parent = path.at(-1);
if (parent == null) return non_hoistable;
const grandparent = path.at(-2);
/** @type {RegularElement | null} */
let element = null;
/** @type {string | null} */
let event_name = null;
if (parent.type === 'OnDirective') {
element = /** @type {RegularElement} */ (grandparent);
event_name = parent.name;
} else if (
parent.type === 'ExpressionTag' &&
grandparent?.type === 'Attribute' &&
is_event_attribute(grandparent)
) {
element = /** @type {RegularElement} */ (path.at(-3));
const attribute = /** @type {Attribute} */ (grandparent);
event_name = get_attribute_event_name(attribute.name);
}
if (element && event_name) {
if (
element.type !== 'RegularElement' ||
element.metadata.has_spread ||
!is_delegated(event_name)
) {
return non_hoistable;
}
} else if (parent.type !== 'FunctionDeclaration' && parent.type !== 'VariableDeclarator') {
return non_hoistable;
}
}
}
// If the binding is exported, bail-out
if (context.state.analysis.exports.find((node) => node.name === handler.name)) {
return non_hoistable;
}
if (binding !== null && binding.initial !== null && !binding.mutated && !binding.is_called) {
const binding_type = binding.initial.type;
if (
binding_type === 'ArrowFunctionExpression' ||
binding_type === 'FunctionDeclaration' ||
binding_type === 'FunctionExpression'
) {
target_function = binding.initial;
}
}
}
// If we can't find a function, bail-out
if (target_function == null) return non_hoistable;
// If the function is marked as non-hoistable, bail-out
if (target_function.metadata.hoistable === 'impossible') return non_hoistable;
// If the function has more than one arg, then bail-out
if (target_function.params.length > 1) return non_hoistable;
const visited_references = new Set();
const scope = target_function.metadata.scope;
for (const [reference] of scope.references) {
// Bail-out if the arguments keyword is used
if (reference === 'arguments') return non_hoistable;
// Bail-out if references a store subscription
if (scope.get(`$${reference}`)?.kind === 'store_sub') return non_hoistable;
const binding = scope.get(reference);
const local_binding = context.state.scope.get(reference);
// If we are referencing a binding that is shadowed in another scope then bail out.
if (local_binding !== null && binding !== null && local_binding.node !== binding.node) {
return non_hoistable;
}
// If we have multiple references to the same store using $ prefix, bail out.
if (
binding !== null &&
binding.kind === 'store_sub' &&
visited_references.has(reference.slice(1))
) {
return non_hoistable;
}
// If we reference the index within an each block, then bail-out.
if (binding !== null && binding.initial?.type === 'EachBlock') return non_hoistable;
if (
binding !== null &&
// Bail-out if the the binding is a rest param
(binding.declaration_kind === 'rest_param' ||
// Bail-out if we reference anything from the EachBlock (for now) that mutates in non-runes mode,
(((!context.state.analysis.runes && binding.kind === 'each') ||
// or any normal not reactive bindings that are mutated.
binding.kind === 'normal' ||
// or any reactive imports (those are rewritten) (can only happen in legacy mode)
binding.kind === 'legacy_reactive_import') &&
binding.mutated))
) {
return non_hoistable;
}
visited_references.add(reference);
}
return { type: 'hoistable', function: target_function };
}
/**
* @param {string} event_name
*/
function get_attribute_event_name(event_name) {
event_name = event_name.slice(2);
if (is_capture_event(event_name)) {
event_name = event_name.slice(0, -7);
}
return event_name;
}
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