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avoid mutations

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pull/12916/head
Rich Harris 2 years ago
parent ab6b3542dc
commit 810817a3de
2 changed files with 164 additions and 58 deletions
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144
packages/svelte/src/internal/client/proxy.js
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@ -63,40 +63,42 @@ export function proxy(value, parent = null, prev) {
}
return new Proxy(/** @type {any} */ (value), {
defineProperty(target, prop, descriptor) {
if (descriptor.value) {
const s = sources.get(prop);
if (s !== undefined) set(s, proxy(descriptor.value, metadata));
defineProperty(_, prop, descriptor) {
if (
!('value' in descriptor) ||
descriptor.configurable === false ||
descriptor.enumerable === false ||
descriptor.writable === false
) {
e.state_descriptors_fixed();
}
var value = descriptor.value;
var s = sources.get(prop);
if (s === undefined) {
s = source(value);
sources.set(prop, s);
} else {
set(s, proxy(value, metadata));
}
return Reflect.defineProperty(target, prop, descriptor);
return true;
},
deleteProperty(target, prop) {
const s = sources.get(prop);
const boolean = delete target[prop];
var s = sources.get(prop);
var exists = s !== undefined ? s.v !== UNINITIALIZED : prop in target;
// If we have mutated an array directly, and the deletion
// was successful we will also need to update the length
// before updating the field or the version. This is to
// ensure any effects observing length can execute before
// effects that listen to the fields – otherwise they will
// operate an an index that no longer exists.
if (is_proxied_array && boolean) {
const ls = sources.get('length');
const length = target.length - 1;
if (ls !== undefined && ls.v !== length) {
set(ls, length);
}
if (s !== undefined) {
set(s, UNINITIALIZED);
}
if (s !== undefined) set(s, UNINITIALIZED);
if (boolean) {
if (exists) {
update_version(version);
}
return boolean;
return exists;
},
get(target, prop, receiver) {
@ -108,31 +110,44 @@ export function proxy(value, parent = null, prev) {
return value;
}
let s = sources.get(prop);
var s = sources.get(prop);
var exists = prop in target;
// create a source, but only if it's an own property and not a prototype property
if (s === undefined && (!(prop in target) || get_descriptor(target, prop)?.writable)) {
s = source(proxy(target[prop], metadata));
if (s === undefined && (!exists || get_descriptor(target, prop)?.writable)) {
s = source(proxy(exists ? target[prop] : UNINITIALIZED, metadata));
sources.set(prop, s);
}
if (s !== undefined) {
const value = get(s);
return value === UNINITIALIZED ? undefined : value;
var v = get(s);
return v === UNINITIALIZED ? undefined : v;
}
return Reflect.get(target, prop, receiver);
},
getOwnPropertyDescriptor(target, prop) {
const descriptor = Reflect.getOwnPropertyDescriptor(target, prop);
var descriptor = Reflect.getOwnPropertyDescriptor(target, prop);
if (descriptor && 'value' in descriptor) {
const s = sources.get(prop);
var s = sources.get(prop);
if (s) {
descriptor.value = get(s);
}
} else if (descriptor === undefined) {
var source = sources.get(prop);
var value = source?.v;
if (source !== undefined && value !== UNINITIALIZED) {
return {
enumerable: true,
configurable: true,
value,
writable: true
};
}
}
return descriptor;
@ -147,9 +162,9 @@ export function proxy(value, parent = null, prev) {
return true;
}
const has = Reflect.has(target, prop);
var s = sources.get(prop);
var has = (s !== undefined && s.v !== UNINITIALIZED) || Reflect.has(target, prop);
let s = sources.get(prop);
if (
s !== undefined ||
(current_effect !== null && (!has || get_descriptor(target, prop)?.writable))
@ -158,35 +173,37 @@ export function proxy(value, parent = null, prev) {
s = source(has ? proxy(target[prop], metadata) : UNINITIALIZED);
sources.set(prop, s);
}
const value = get(s);
var value = get(s);
if (value === UNINITIALIZED) {
return false;
}
}
return has;
},
set(target, prop, value, receiver) {
let s = sources.get(prop);
var s = sources.get(prop);
var has = prop in target;
// If we haven't yet created a source for this property, we need to ensure
// we do so otherwise if we read it later, then the write won't be tracked and
// the heuristics of effects will be different vs if we had read the proxied
// object property before writing to that property.
if (s === undefined) {
// the read creates a signal
untrack(() => receiver[prop]);
s = sources.get(prop);
if (!has || get_descriptor(target, prop)?.writable) {
s = source(undefined);
set(s, proxy(value, metadata));
sources.set(prop, s);
}
if (s !== undefined) {
} else {
has = s.v !== UNINITIALIZED;
set(s, proxy(value, metadata));
}
const not_has = !(prop in target);
if (DEV) {
/** @type {ProxyMetadata | undefined} */
const prop_metadata = value?.[STATE_SYMBOL_METADATA];
var prop_metadata = value?.[STATE_SYMBOL_METADATA];
if (prop_metadata && prop_metadata?.parent !== metadata) {
widen_ownership(metadata, prop_metadata);
}
@ -195,9 +212,9 @@ export function proxy(value, parent = null, prev) {
// variable.length = value -> clear all signals with index >= value
if (is_proxied_array && prop === 'length') {
for (let i = value; i < target.length; i += 1) {
const s = sources.get(i + '');
if (s !== undefined) set(s, UNINITIALIZED);
for (var i = value; i < target.length; i += 1) {
var other_s = sources.get(i + '');
if (other_s !== undefined) set(other_s, UNINITIALIZED);
}
}
@ -206,22 +223,25 @@ export function proxy(value, parent = null, prev) {
// Set the new value before updating any signals so that any listeners get the new value
if (descriptor?.set) {
descriptor.set.call(receiver, value);
} else {
target[prop] = value;
}
if (not_has) {
if (!has) {
// If we have mutated an array directly, we might need to
// signal that length has also changed. Do it before updating the version
// to ensure that iterating over the array as a result of a version update
// signal that length has also changed. Do it before updating metadata
// to ensure that iterating over the array as a result of a metadata update
// will not cause the length to be out of sync.
if (is_proxied_array) {
const ls = sources.get('length');
const length = target.length;
if (ls !== undefined && ls.v !== length) {
set(ls, length);
if (is_proxied_array && typeof prop === 'string') {
var ls = sources.get('length');
if (ls !== undefined) {
var n = Number(prop);
if (Number.isInteger(n) && n >= ls.v) {
set(ls, n + 1);
}
}
}
update_version(version);
}
@ -230,7 +250,19 @@ export function proxy(value, parent = null, prev) {
ownKeys(target) {
get(version);
return Reflect.ownKeys(target);
var own_keys = Reflect.ownKeys(target).filter((key) => {
var source = sources.get(key);
return source === undefined || source.v !== UNINITIALIZED;
});
for (var [key, source] of sources) {
if (source.v !== UNINITIALIZED && !(key in target)) {
own_keys.push(key);
}
}
return own_keys;
},
setPrototypeOf() {

74
packages/svelte/src/internal/client/proxy.test.ts
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@ -0,0 +1,74 @@
import { proxy } from './proxy';
import { assert, test } from 'vitest';
test('does not mutate the original object', () => {
const original = { x: 1 };
const state = proxy(original);
state.x = 2;
assert.equal(original.x, 1);
assert.equal(state.x, 2);
});
test('preserves getters', () => {
let count = 0;
const original = {
count: 0,
get x() {
this.count += 1;
count += 1;
return 42;
}
};
const state = proxy(original);
// eslint-disable-next-line @typescript-eslint/no-unused-expressions
state.x;
// eslint-disable-next-line @typescript-eslint/no-unused-expressions
state.x;
assert.equal(original.count, 0);
assert.equal(count, 2);
assert.equal(state.count, 2);
});
test('defines a property', () => {
const original = { y: 0 };
const state = proxy<any>(original);
let value = 0;
Object.defineProperty(state, 'x', {
value: 1
});
Object.defineProperty(state, 'y', {
value: 1
});
assert.equal(state.x, 1);
assert.deepEqual(Object.getOwnPropertyDescriptor(state, 'x'), {
configurable: true,
writable: true,
value: 1,
enumerable: true
});
assert.ok(!('x' in original));
assert.deepEqual(Object.getOwnPropertyDescriptor(original, 'y'), {
configurable: true,
writable: true,
value: 0,
enumerable: true
});
assert.throws(
() =>
Object.defineProperty(state, 'x', {
get: () => value,
set: (v) => (value = v)
}),
/state_descriptors_fixed/
);
});
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