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fix: rewrite destructuring logic to handle iterators (#15813)

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* fix: wrap array destructuring in spread to avoid iterator edge case

* spread at `tmp` declaration

* completely rewrite destructuring handling

* only wrap in iife if necessary

* oops

* minor style tweaks

* separate visitors

* tweak

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>
pull/15905/head
ComputerGuy 5 months ago committed by GitHub
parent 8fc8bc79d1
commit 7826ebaccc
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GPG Key ID: B5690EEEBB952194
7 changed files with 141 additions and 74 deletions
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5
.changeset/serious-moles-yell.md
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@ -0,0 +1,5 @@
---
'svelte': patch
---
fix: rewrite destructuring logic to handle iterators

69
packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js
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@ -2,7 +2,7 @@
/** @import { Binding } from '#compiler' */
/** @import { ComponentClientTransformState, ComponentContext } from '../types' */
import { dev } from '../../../../state.js';
import { extract_paths } from '../../../../utils/ast.js';
import { build_pattern, extract_paths } from '../../../../utils/ast.js';
import * as b from '#compiler/builders';
import * as assert from '../../../../utils/assert.js';
import { get_rune } from '../../../scope.js';
@ -141,20 +141,20 @@ export function VariableDeclaration(node, context) {
b.declarator(declarator.id, create_state_declarator(declarator.id, value))
);
} else {
const tmp = context.state.scope.generate('tmp');
const paths = extract_paths(declarator.id);
const [pattern, replacements] = build_pattern(declarator.id, context.state.scope);
declarations.push(
b.declarator(b.id(tmp), value),
...paths.map((path) => {
const value = path.expression?.(b.id(tmp));
const binding = context.state.scope.get(/** @type {Identifier} */ (path.node).name);
return b.declarator(
path.node,
binding?.kind === 'state' || binding?.kind === 'raw_state'
? create_state_declarator(binding.node, value)
: value
);
})
b.declarator(pattern, value),
.../** @type {[Identifier, Identifier][]} */ ([...replacements]).map(
([original, replacement]) => {
const binding = context.state.scope.get(original.name);
return b.declarator(
original,
binding?.kind === 'state' || binding?.kind === 'raw_state'
? create_state_declarator(binding.node, replacement)
: replacement
);
}
)
);
}
@ -170,8 +170,7 @@ export function VariableDeclaration(node, context) {
)
);
} else {
const bindings = extract_paths(declarator.id);
const [pattern, replacements] = build_pattern(declarator.id, context.state.scope);
const init = /** @type {CallExpression} */ (declarator.init);
/** @type {Identifier} */
@ -189,10 +188,16 @@ export function VariableDeclaration(node, context) {
);
}
for (let i = 0; i < bindings.length; i++) {
const binding = bindings[i];
for (let i = 0; i < replacements.size; i++) {
const [original, replacement] = [...replacements][i];
declarations.push(
b.declarator(binding.node, b.call('$.derived', b.thunk(binding.expression(rhs))))
b.declarator(
original,
b.call(
'$.derived',
b.arrow([], b.block([b.let(pattern, rhs), b.return(replacement)]))
)
)
);
}
}
@ -304,19 +309,19 @@ function create_state_declarators(declarator, { scope, analysis }, value) {
];
}
const tmp = scope.generate('tmp');
const paths = extract_paths(declarator.id);
const [pattern, replacements] = build_pattern(declarator.id, scope);
return [
b.declarator(b.id(tmp), value),
...paths.map((path) => {
const value = path.expression?.(b.id(tmp));
const binding = scope.get(/** @type {Identifier} */ (path.node).name);
return b.declarator(
path.node,
binding?.kind === 'state'
? b.call('$.mutable_source', value, analysis.immutable ? b.true : undefined)
: value
);
})
b.declarator(pattern, value),
.../** @type {[Identifier, Identifier][]} */ ([...replacements]).map(
([original, replacement]) => {
const binding = scope.get(original.name);
return b.declarator(
original,
binding?.kind === 'state'
? b.call('$.mutable_source', replacement, analysis.immutable ? b.true : undefined)
: replacement
);
}
)
];
}

13
packages/svelte/src/compiler/phases/3-transform/server/visitors/VariableDeclaration.js
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@ -3,7 +3,7 @@
/** @import { Context } from '../types.js' */
/** @import { ComponentAnalysis } from '../../../types.js' */
/** @import { Scope } from '../../../scope.js' */
import { build_fallback, extract_paths } from '../../../../utils/ast.js';
import { build_pattern, build_fallback, extract_paths } from '../../../../utils/ast.js';
import * as b from '#compiler/builders';
import { get_rune } from '../../../scope.js';
import { walk } from 'zimmerframe';
@ -188,13 +188,10 @@ function create_state_declarators(declarator, scope, value) {
return [b.declarator(declarator.id, value)];
}
const tmp = scope.generate('tmp');
const paths = extract_paths(declarator.id);
const [pattern, replacements] = build_pattern(declarator.id, scope);
return [
b.declarator(b.id(tmp), value), // TODO inject declarator for opts, so we can use it below
...paths.map((path) => {
const value = path.expression?.(b.id(tmp));
return b.declarator(path.node, value);
})
b.declarator(pattern, value),
// TODO inject declarator for opts, so we can use it below
...[...replacements].map(([original, replacement]) => b.declarator(original, replacement))
];
}

67
packages/svelte/src/compiler/phases/3-transform/shared/assignments.js
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@ -1,7 +1,7 @@
/** @import { AssignmentExpression, AssignmentOperator, Expression, Node, Pattern } from 'estree' */
/** @import { AssignmentExpression, AssignmentOperator, Expression, Identifier, Node, Pattern } from 'estree' */
/** @import { Context as ClientContext } from '../client/types.js' */
/** @import { Context as ServerContext } from '../server/types.js' */
import { extract_paths, is_expression_async } from '../../../utils/ast.js';
import { build_pattern, is_expression_async } from '../../../utils/ast.js';
import * as b from '#compiler/builders';
/**
@ -23,21 +23,23 @@ export function visit_assignment_expression(node, context, build_assignment) {
let changed = false;
const assignments = extract_paths(node.left).map((path) => {
const value = path.expression?.(rhs);
const [pattern, replacements] = build_pattern(node.left, context.state.scope);
let assignment = build_assignment('=', path.node, value, context);
if (assignment !== null) changed = true;
return (
assignment ??
b.assignment(
'=',
/** @type {Pattern} */ (context.visit(path.node)),
/** @type {Expression} */ (context.visit(value))
)
);
});
const assignments = [
b.let(pattern, rhs),
...[...replacements].map(([original, replacement]) => {
let assignment = build_assignment(node.operator, original, replacement, context);
if (assignment !== null) changed = true;
return b.stmt(
assignment ??
b.assignment(
node.operator,
/** @type {Identifier} */ (context.visit(original)),
/** @type {Expression} */ (context.visit(replacement))
)
);
})
];
if (!changed) {
// No change to output -> nothing to transform -> we can keep the original assignment
@ -45,25 +47,36 @@ export function visit_assignment_expression(node, context, build_assignment) {
}
const is_standalone = /** @type {Node} */ (context.path.at(-1)).type.endsWith('Statement');
const sequence = b.sequence(assignments);
const block = b.block(assignments);
if (!is_standalone) {
// this is part of an expression, we need the sequence to end with the value
sequence.expressions.push(rhs);
block.body.push(b.return(rhs));
}
if (should_cache) {
// the right hand side is a complex expression, wrap in an IIFE to cache it
const iife = b.arrow([rhs], sequence);
if (is_standalone && !should_cache) {
return block;
}
const iife_is_async =
is_expression_async(value) ||
assignments.some((assignment) => is_expression_async(assignment));
const iife = b.arrow(should_cache ? [rhs] : [], block);
return iife_is_async ? b.await(b.call(b.async(iife), value)) : b.call(iife, value);
}
const iife_is_async =
is_expression_async(value) ||
assignments.some(
(assignment) =>
(assignment.type === 'ExpressionStatement' &&
is_expression_async(assignment.expression)) ||
(assignment.type === 'VariableDeclaration' &&
assignment.declarations.some(
(declaration) =>
is_expression_async(declaration.id) ||
(declaration.init && is_expression_async(declaration.init))
))
);
return sequence;
return iife_is_async
? b.await(b.call(b.async(iife), should_cache ? value : undefined))
: b.call(iife, should_cache ? value : undefined);
}
if (node.left.type !== 'Identifier' && node.left.type !== 'MemberExpression') {

5
packages/svelte/src/compiler/phases/scope.js
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@ -630,9 +630,10 @@ export class Scope {
/**
* @param {string} preferred_name
* @param {(name: string, counter: number) => string} [generator]
* @returns {string}
*/
generate(preferred_name) {
generate(preferred_name, generator = (name, counter) => `${name}_${counter}`) {
if (this.#porous) {
return /** @type {Scope} */ (this.parent).generate(preferred_name);
}
@ -647,7 +648,7 @@ export class Scope {
this.root.conflicts.has(name) ||
is_reserved(name)
) {
name = `${preferred_name}_${n++}`;
name = generator(preferred_name, n++);
}
this.references.set(name, []);

46
packages/svelte/src/compiler/utils/ast.js
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@ -1,7 +1,8 @@
/** @import { AST } from '#compiler' */
/** @import { AST, Scope } from '#compiler' */
/** @import * as ESTree from 'estree' */
import { walk } from 'zimmerframe';
import * as b from '#compiler/builders';
import is_reference from 'is-reference';
/**
* Gets the left-most identifier of a member expression or identifier.
@ -128,6 +129,49 @@ export function unwrap_pattern(pattern, nodes = []) {
return nodes;
}
/**
* @param {ESTree.Pattern} id
* @param {Scope} scope
* @returns {[ESTree.Pattern, Map<ESTree.Identifier | ESTree.MemberExpression, ESTree.Identifier>]}
*/
export function build_pattern(id, scope) {
/** @type {Map<ESTree.Identifier | ESTree.MemberExpression, ESTree.Identifier>} */
const map = new Map();
/** @type {Map<string, string>} */
const names = new Map();
let counter = 0;
for (const node of unwrap_pattern(id)) {
const name = scope.generate(`$$${++counter}`, (_, counter) => `$$${counter}`);
map.set(node, b.id(name));
if (node.type === 'Identifier') {
names.set(node.name, name);
}
}
const pattern = walk(id, null, {
Identifier(node, context) {
if (is_reference(node, /** @type {ESTree.Pattern} */ (context.path.at(-1)))) {
const name = names.get(node.name);
if (name) return b.id(name);
}
},
MemberExpression(node, context) {
const n = map.get(node);
if (n) return n;
context.next();
}
});
return [pattern, map];
}
/**
* Extracts all identifiers from a pattern.
* @param {ESTree.Pattern} pattern

10
packages/svelte/tests/snapshot/samples/destructured-assignments/_expected/client/index.svelte.js
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@ -7,10 +7,12 @@ let c = 3;
let d = 4;
export function update(array) {
(
$.set(a, array[0], true),
$.set(b, array[1], true)
);
{
let [$$1, $$2] = array;
$.set(a, $$1, true);
$.set(b, $$2, true);
};
[c, d] = array;
}
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