fix: use state instead of source in reactive classes
#16239
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,9 +1,10 @@ | ||
| /** @import { Reaction, Source } from '#client' */ | ||
| import { DEV } from 'esm-env'; | ||
| import { set, source, state } from '../internal/client/reactivity/sources.js'; | ||
| import { label, tag } from '../internal/client/dev/tracing.js'; | ||
| import { active_reaction, get } from '../internal/client/runtime.js'; | ||
| import { increment } from './utils.js'; | ||
| import { teardown } from '../internal/client/reactivity/effects.js'; | ||
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| /** | ||
| * A reactive version of the built-in [`Map`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map) object. | ||
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@@ -56,13 +57,24 @@ export class SvelteMap extends Map { | |
| #sources = new Map(); | ||
| #version = state(0); | ||
| #size = state(0); | ||
| /**@type {Reaction | null} */ | ||
| #initial_reaction = null; | ||
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| /** | ||
| * @param {Iterable<readonly [K, V]> | null | undefined} [value] | ||
| */ | ||
| constructor(value) { | ||
| super(); | ||
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| if (active_reaction !== null) { | ||
| this.#initial_reaction = active_reaction; | ||
| // since we only need `initial_reaction` as long as we are in a derived/effect we can | ||
| // safely create a teardown function that will reset it to null and allow for GC | ||
| teardown(() => { | ||
| this.#initial_reaction = null; | ||
| }); | ||
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There was a problem hiding this comment. presumably if there's a situation that would create a memory leak with this (which I guess means smuggling a reference to the map to something outside the current reaction?), do we therefore need a way to run code as soon as the current reaction has finished updating? #16316 There was a problem hiding this comment. The alternative is to use a weak ref to reference the reaction. Perf impact should be close to zero since it only applies once for new sources There was a problem hiding this comment. We could also use WeakRef, we were discussing with Simon this morning that this seems the perfect use case for it There was a problem hiding this comment. I've pushed a commit to use There was a problem hiding this comment. Not sure I love the WeakRef solution tbh — it increases overall memory usage (since every map/set now has to have a WeakRef instance) and slows down every There was a problem hiding this comment. Consider it to be the same as previous values in teardown. It's not about if it's right or wrong, it's about the expectations and not making it confusing on the DX side of things There was a problem hiding this comment. That will not introduce a leak...to introduce a leak you would do some weird as Simon pointed out
There was a problem hiding this comment. Hm, not sure what I am missing here. Why it won't introduce a leak? As long as I hold to the map somewhere I hold to the There was a problem hiding this comment. Duh I misread your code...yeah that will "leak" although only until There was a problem hiding this comment. Yeah, so my point is that if I write to |
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| } | ||
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| if (DEV) { | ||
| // If the value is invalid then the native exception will fire here | ||
| value = new Map(value); | ||
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@@ -79,6 +91,22 @@ export class SvelteMap extends Map { | |
| } | ||
| } | ||
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| /** | ||
| * If the active_reaction is the same as the reaction that created this SvelteMap, | ||
| * we use state so that it will not be a dependency of the reaction. Otherwise we | ||
| * use source so it will be. | ||
| * | ||
| * @template T | ||
| * @param {T} value | ||
| * @returns {Source<T>} | ||
| */ | ||
| #source(value) { | ||
| if (this.#initial_reaction === active_reaction) { | ||
| return state(value); | ||
| } | ||
| return source(value); | ||
| } | ||
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| /** @param {K} key */ | ||
| has(key) { | ||
| var sources = this.#sources; | ||
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@@ -87,7 +115,7 @@ export class SvelteMap extends Map { | |
| if (s === undefined) { | ||
| var ret = super.get(key); | ||
| if (ret !== undefined) { | ||
| s = this.#source(0); | ||
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| if (DEV) { | ||
| tag(s, `SvelteMap get(${label(key)})`); | ||
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@@ -123,7 +151,7 @@ export class SvelteMap extends Map { | |
| if (s === undefined) { | ||
| var ret = super.get(key); | ||
| if (ret !== undefined) { | ||
| s = this.#source(0); | ||
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| if (DEV) { | ||
| tag(s, `SvelteMap get(${label(key)})`); | ||
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@@ -154,7 +182,7 @@ export class SvelteMap extends Map { | |
| var version = this.#version; | ||
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| if (s === undefined) { | ||
| s = this.#source(0); | ||
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| if (DEV) { | ||
| tag(s, `SvelteMap get(${label(key)})`); | ||
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@@ -219,8 +247,7 @@ export class SvelteMap extends Map { | |
| if (this.#size.v !== sources.size) { | ||
| for (var key of super.keys()) { | ||
| if (!sources.has(key)) { | ||
| var s = this.#source(0); | ||
| if (DEV) { | ||
| tag(s, `SvelteMap get(${label(key)})`); | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,27 +1,101 @@ | ||
| <script> | ||
| import { SvelteMap } from 'svelte/reactivity'; | ||
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| let outside_basic = $state(false); | ||
| let outside_basic_map = new SvelteMap(); | ||
| const throw_basic = $derived.by(() => { | ||
| outside_basic_map.set(1, 1); | ||
| return outside_basic_map; | ||
| }); | ||
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| let inside_basic = $state(false); | ||
| const works_basic = $derived.by(() => { | ||
| let inside = new SvelteMap(); | ||
| inside.set(1, 1); | ||
| return inside; | ||
| }); | ||
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| let outside_has = $state(false); | ||
| let outside_has_map = new SvelteMap([[1, 1]]); | ||
| const throw_has = $derived.by(() => { | ||
| outside_has_map.has(1); | ||
| outside_has_map.set(1, 2); | ||
| return outside_has_map; | ||
| }); | ||
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| let inside_has = $state(false); | ||
| const works_has = $derived.by(() => { | ||
| let inside = new SvelteMap([[1, 1]]); | ||
| inside.has(1); | ||
| inside.set(1, 1); | ||
| return inside; | ||
| }); | ||
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| let outside_get = $state(false); | ||
| let outside_get_map = new SvelteMap([[1, 1]]); | ||
| const throw_get = $derived.by(() => { | ||
| outside_get_map.get(1); | ||
| outside_get_map.set(1, 2); | ||
| return outside_get_map; | ||
| }); | ||
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| let inside_get = $state(false); | ||
| const works_get = $derived.by(() => { | ||
| let inside = new SvelteMap([[1, 1]]); | ||
| inside.get(1); | ||
| inside.set(1, 1); | ||
| return inside; | ||
| }); | ||
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| let outside_values = $state(false); | ||
| let outside_values_map = new SvelteMap([[1, 1]]); | ||
| const throw_values = $derived.by(() => { | ||
| outside_values_map.values(1); | ||
| outside_values_map.set(1, 2); | ||
| return outside_values_map; | ||
| }); | ||
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| let inside_values = $state(false); | ||
| const works_values = $derived.by(() => { | ||
| let inside = new SvelteMap([[1, 1]]); | ||
| inside.values(); | ||
| inside.set(1, 1); | ||
| return inside; | ||
| }); | ||
| </script> | ||
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| <button onclick={() => (outside_basic = true)}>external</button> | ||
| {#if outside_basic} | ||
| {throw_basic} | ||
| {/if} | ||
| <button onclick={() => (inside_basic = true)}>internal</button> | ||
| {#if inside_basic} | ||
| {works_basic} | ||
| {/if} | ||
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| <button onclick={() => (outside_has = true)}>external</button> | ||
| {#if outside_has} | ||
| {throw_has} | ||
| {/if} | ||
| <button onclick={() => (inside_has = true)}>internal</button> | ||
| {#if inside_has} | ||
| {works_has} | ||
| {/if} | ||
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| <button onclick={() => (outside_get = true)}>external</button> | ||
| {#if outside_get} | ||
| {throw_get} | ||
| {/if} | ||
| <button onclick={() => (inside_get = true)}>internal</button> | ||
| {#if inside_get} | ||
| {works_get} | ||
| {/if} | ||
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| <button onclick={() => (outside_values = true)}>external</button> | ||
| {#if outside_values} | ||
| {throw_values} | ||
| {/if} | ||
| <button onclick={() => (inside_values = true)}>internal</button> | ||
| {#if inside_values} | ||
| {works_values} | ||
| {/if} |
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Wondering if there are cases when map still lives, while the reaction could have been GCed and this would prevent it?
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Yeah I was wondering about that too...technically it shouldn't be the case because either there's no active reaction (it's outside of a derived/effect) or it's inside it but this means that when the derived/effect is no longer used the function should be GCd and everything inside it too...but I need to do a better check
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Maybe this can become
initial_reaction = WeakSet(active_reaction)and we can check withthis.initial_reaction.has(active_reaction)?There was a problem hiding this comment.
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Just for the sake of history, I've also discovered there is a WeakRef struct that could be alternative here. In case of any future issues might be a possible alternative implementation