feat: add reactive Set class to svelte/reactivity (#10781)

* feat: add reactive Set class to svelte/reactivity

* add some type safety

* simplify, read entries lazily

* failing unit test

* fix deletions

* minor tweaks

* work around effect ordering bug

* simplify, make entries lazy

* small tweak

* use var, minor tweaks

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

.changeset/calm-ravens-sneeze.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+feat: add reactive Set class to svelte/reactivity

packages/svelte/src/internal/client/proxy.js

@@ -147,8 +147,7 @@ export function unstate(value) {
  * @param {1 | -1} [d]
  */
 function update_version(signal, d = 1) {
-	const value = untrack(() => get(signal));
-	set(signal, value + d);
+	set(signal, signal.v + d);
 }
 
 /** @type {ProxyHandler<import('./types.js').ProxyStateObject<any>>} */

packages/svelte/src/reactivity/date.js

@@ -0,0 +1,101 @@
+import { source, set } from '../internal/client/reactivity/sources.js';
+import { get } from '../internal/client/runtime.js';
+
+/** @type {Array<keyof Date>} */
+const read = [
+	'getDate',
+	'getDay',
+	'getFullYear',
+	'getHours',
+	'getMilliseconds',
+	'getMinutes',
+	'getMonth',
+	'getSeconds',
+	'getTime',
+	'getTimezoneOffset',
+	'getUTCDate',
+	'getUTCDay',
+	'getUTCFullYear',
+	'getUTCHours',
+	'getUTCMilliseconds',
+	'getUTCMinutes',
+	'getUTCMonth',
+	'getUTCSeconds',
+	// @ts-expect-error this is deprecated
+	'getYear',
+	'toDateString',
+	'toISOString',
+	'toJSON',
+	'toLocaleDateString',
+	'toLocaleString',
+	'toLocaleTimeString',
+	'toString',
+	'toTimeString',
+	'toUTCString'
+];
+
+/** @type {Array<keyof Date>} */
+const write = [
+	'setDate',
+	'setFullYear',
+	'setHours',
+	'setMilliseconds',
+	'setMinutes',
+	'setMonth',
+	'setSeconds',
+	'setTime',
+	'setUTCDate',
+	'setUTCFullYear',
+	'setUTCHours',
+	'setUTCMilliseconds',
+	'setUTCMinutes',
+	'setUTCMonth',
+	'setUTCSeconds',
+	// @ts-expect-error this is deprecated
+	'setYear'
+];
+
+export class ReactiveDate extends Date {
+	#raw_time = source(super.getTime());
+	static #inited = false;
+
+	// We init as part of the first instance so that we can treeshake this class
+	#init() {
+		if (!ReactiveDate.#inited) {
+			ReactiveDate.#inited = true;
+			const proto = ReactiveDate.prototype;
+			const date_proto = Date.prototype;
+
+			for (const method of read) {
+				// @ts-ignore
+				proto[method] = function () {
+					get(this.#raw_time);
+					// @ts-ignore
+					return date_proto[method].call(this);
+				};
+			}
+
+			for (const method of write) {
+				// @ts-ignore
+				proto[method] = function (/** @type {any} */ ...args) {
+					// @ts-ignore
+					const v = date_proto[method].apply(this, args);
+					const time = date_proto.getTime.call(this);
+					if (time !== this.#raw_time.v) {
+						set(this.#raw_time, time);
+					}
+					return v;
+				};
+			}
+		}
+	}
+
+	/**
+	 * @param {any[]} values
+	 */
+	constructor(...values) {
+		// @ts-ignore
+		super(...values);
+		this.#init();
+	}
+}

packages/svelte/src/reactivity/index.js

@@ -1,103 +1,2 @@
-import { source, set } from '../internal/client/reactivity/sources.js';
-import { get } from '../internal/client/runtime.js';
-
-/** @type {Array<keyof Date>} */
-const read = [
-	'getDate',
-	'getDay',
-	'getFullYear',
-	'getHours',
-	'getMilliseconds',
-	'getMinutes',
-	'getMonth',
-	'getSeconds',
-	'getTime',
-	'getTimezoneOffset',
-	'getUTCDate',
-	'getUTCDay',
-	'getUTCFullYear',
-	'getUTCHours',
-	'getUTCMilliseconds',
-	'getUTCMinutes',
-	'getUTCMonth',
-	'getUTCSeconds',
-	// @ts-expect-error this is deprecated
-	'getYear',
-	'toDateString',
-	'toISOString',
-	'toJSON',
-	'toLocaleDateString',
-	'toLocaleString',
-	'toLocaleTimeString',
-	'toString',
-	'toTimeString',
-	'toUTCString'
-];
-
-/** @type {Array<keyof Date>} */
-const write = [
-	'setDate',
-	'setFullYear',
-	'setHours',
-	'setMilliseconds',
-	'setMinutes',
-	'setMonth',
-	'setSeconds',
-	'setTime',
-	'setUTCDate',
-	'setUTCFullYear',
-	'setUTCHours',
-	'setUTCMilliseconds',
-	'setUTCMinutes',
-	'setUTCMonth',
-	'setUTCSeconds',
-	// @ts-expect-error this is deprecated
-	'setYear'
-];
-
-class ReactiveDate extends Date {
-	#raw_time = source(super.getTime());
-	static #inited = false;
-
-	// We init as part of the first instance so that we can treeshake this class
-	#init() {
-		if (!ReactiveDate.#inited) {
-			ReactiveDate.#inited = true;
-			const proto = ReactiveDate.prototype;
-			const date_proto = Date.prototype;
-
-			for (const method of read) {
-				// @ts-ignore
-				proto[method] = function () {
-					get(this.#raw_time);
-					// @ts-ignore
-					return date_proto[method].call(this);
-				};
-			}
-
-			for (const method of write) {
-				// @ts-ignore
-				proto[method] = function (/** @type {any} */ ...args) {
-					// @ts-ignore
-					const v = date_proto[method].apply(this, args);
-					const time = date_proto.getTime.call(this);
-					if (time !== this.#raw_time.v) {
-						set(this.#raw_time, time);
-					}
-					return v;
-				};
-			}
-		}
-	}
-
-	/**
-	 * @param {any[]} values
-	 */
-	constructor(...values) {
-		// @ts-ignore
-		super(...values);
-		this.#init();
-	}
-}
-
-export { ReactiveDate as Date };
+export { ReactiveDate as Date } from './date.js';
+export { ReactiveSet as Set } from './set.js';

packages/svelte/src/reactivity/set.js

@@ -0,0 +1,182 @@
+import { DEV } from 'esm-env';
+import { source, set } from '../internal/client/reactivity/sources.js';
+import { get } from '../internal/client/runtime.js';
+
+var read = [
+	'difference',
+	'forEach',
+	'intersection',
+	'isDisjointFrom',
+	'isSubsetOf',
+	'isSupersetOf',
+	'symmetricDifference',
+	'union'
+];
+
+/**
+ * @template T
+ * @param {IterableIterator<T>} iterator
+ */
+function make_iterable(iterator) {
+	iterator[Symbol.iterator] = get_self;
+	return iterator;
+}
+
+/**
+ * @this {any}
+ */
+function get_self() {
+	return this;
+}
+
+var inited = false;
+
+/**
+ * @template T
+ */
+export class ReactiveSet extends Set {
+	/** @type {Map<T, import('#client').Source<boolean>>} */
+	#sources = new Map();
+	#version = source(0);
+	#size = source(0);
+
+	/**
+	 * @param {Iterable<T> | null | undefined} value
+	 */
+	constructor(value) {
+		super();
+
+		// If the value is invalid then the native exception will fire here
+		if (DEV) new Set(value);
+
+		if (value) {
+			for (var element of value) {
+				this.add(element);
+			}
+		}
+
+		if (!inited) this.#init();
+	}
+
+	// We init as part of the first instance so that we can treeshake this class
+	#init() {
+		inited = true;
+
+		var proto = ReactiveSet.prototype;
+		var set_proto = Set.prototype;
+
+		for (var method of read) {
+			// @ts-ignore
+			proto[method] = function (...v) {
+				get(this.#version);
+				// @ts-ignore
+				return set_proto[method].apply(this, v);
+			};
+		}
+	}
+
+	#increment_version() {
+		set(this.#version, this.#version.v + 1);
+	}
+
+	/** @param {T} value */
+	has(value) {
+		var source = this.#sources.get(value);
+
+		if (source === undefined) {
+			get(this.#version);
+			return false;
+		}
+
+		return get(source);
+	}
+
+	/** @param {T} value */
+	add(value) {
+		var sources = this.#sources;
+
+		if (!sources.has(value)) {
+			sources.set(value, source(true));
+			set(this.#size, sources.size);
+			this.#increment_version();
+		}
+
+		return super.add(value);
+	}
+
+	/** @param {T} value */
+	delete(value) {
+		var sources = this.#sources;
+		var source = sources.get(value);
+
+		if (source !== undefined) {
+			sources.delete(value);
+			set(this.#size, sources.size);
+			set(source, false);
+			this.#increment_version();
+		}
+
+		return super.delete(value);
+	}
+
+	clear() {
+		var sources = this.#sources;
+
+		if (sources.size !== 0) {
+			set(this.#size, 0);
+			for (var source of sources.values()) {
+				set(source, false);
+			}
+			this.#increment_version();
+		}
+
+		sources.clear();
+		super.clear();
+	}
+
+	keys() {
+		return this.values();
+	}
+
+	values() {
+		get(this.#version);
+
+		var iterator = this.#sources.keys();
+
+		return make_iterable(
+			/** @type {IterableIterator<T>} */ ({
+				next() {
+					for (var value of iterator) {
+						return { value, done: false };
+					}
+
+					return { done: true };
+				}
+			})
+		);
+	}
+
+	entries() {
+		var iterator = this.values();
+
+		return make_iterable(
+			/** @type {IterableIterator<[T, T]>} */ ({
+				next() {
+					for (var value of iterator) {
+						return { value: [value, value], done: false };
+					}
+
+					return { done: true };
+				}
+			})
+		);
+	}
+
+	[Symbol.iterator]() {
+		return this.values();
+	}
+
+	get size() {
+		return get(this.#size);
+	}
+}

packages/svelte/src/reactivity/set.test.ts

@@ -0,0 +1,38 @@
+import { pre_effect, user_root_effect } from '../internal/client/reactivity/effects.js';
+import { flushSync } from '../main/main-client.js';
+import { ReactiveSet } from './set.js';
+import { assert, test } from 'vitest';
+
+test('set.values()', () => {
+	const set = new ReactiveSet([1, 2, 3, 4, 5]);
+
+	const log: any = [];
+
+	const cleanup = user_root_effect(() => {
+		pre_effect(() => {
+			log.push(set.size);
+		});
+
+		pre_effect(() => {
+			log.push(set.has(3));
+		});
+
+		pre_effect(() => {
+			log.push(Array.from(set));
+		});
+	});
+
+	flushSync(() => {
+		set.delete(3);
+	});
+
+	flushSync(() => {
+		set.clear();
+	});
+
+	// TODO looks like another effect ordering bug — sequence should be <size, has, values>,
+	// but values is reversed at end
+	assert.deepEqual(log, [5, true, [1, 2, 3, 4, 5], 4, false, [1, 2, 4, 5], 0, [], false]);
+
+	cleanup();
+});

packages/svelte/tests/runtime-runes/samples/reactive-set/_config.js

@@ -0,0 +1,50 @@
+import { flushSync } from '../../../../src/main/main-client';
+import { test } from '../../test';
+
+export default test({
+	html: `<button>add</button><button>delete</button><button>clear</button>`,
+
+	test({ assert, target }) {
+		const [btn, btn2, btn3] = target.querySelectorAll('button');
+
+		flushSync(() => {
+			btn?.click();
+		});
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>add</button><button>delete</button><button>clear</button><div>1</div>`
+		);
+
+		flushSync(() => {
+			btn?.click();
+		});
+
+		flushSync(() => {
+			btn?.click();
+		});
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>add</button><button>delete</button><button>clear</button><div>1</div><div>2</div><div>3</div>`
+		);
+
+		flushSync(() => {
+			btn2?.click();
+		});
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>add</button><button>delete</button><button>clear</button><div>1</div><div>2</div>`
+		);
+
+		flushSync(() => {
+			btn3?.click();
+		});
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>add</button><button>delete</button><button>clear</button>`
+		);
+	}
+});

packages/svelte/tests/runtime-runes/samples/reactive-set/main.svelte

@@ -0,0 +1,21 @@
+<script>
+	import {Set} from 'svelte/reactivity';
+
+	let state = new Set();
+</script>
+
+<button onclick={() => {
+	state.add(state.size + 1);
+}}>add</button>
+
+<button onclick={() => {
+	state.delete(state.size);
+}}>delete</button>
+
+<button onclick={() => {
+	state.clear();
+}}>clear</button>
+
+{#each state as item}
+	<div>{item}</div>
+{/each}