diff --git a/.changeset/async-store-sub-blocker.md b/.changeset/async-store-sub-blocker.md new file mode 100644 index 0000000000..0222dac846 --- /dev/null +++ b/.changeset/async-store-sub-blocker.md @@ -0,0 +1,5 @@ +--- +'svelte': patch +--- + +fix: block template store subscriptions on the promise that assigns the store diff --git a/packages/svelte/src/compiler/phases/2-analyze/index.js b/packages/svelte/src/compiler/phases/2-analyze/index.js index 1fd83e65b9..45f703901d 100644 --- a/packages/svelte/src/compiler/phases/2-analyze/index.js +++ b/packages/svelte/src/compiler/phases/2-analyze/index.js @@ -1228,6 +1228,23 @@ function calculate_blockers(instance, analysis) { flush_sync_group(); + // a store subscription must wait on whatever blocks the store itself; this must happen + // before function tracing so that functions reading `$store` inherit the blocker + for (const [name, binding] of instance.scope.declarations) { + if (binding.kind !== 'store_sub') continue; + + const store_blocker = instance.scope.get(name.slice(1))?.blocker; + if (!store_blocker) continue; + + if ( + !binding.blocker || + /** @type {ESTree.SimpleLiteral & { value: number }} */ (binding.blocker.property).value < + /** @type {ESTree.SimpleLiteral & { value: number }} */ (store_blocker.property).value + ) { + binding.blocker = store_blocker; + } + } + for (const fn of functions) { /** @type {Set} */ const reads_writes = new Set(); diff --git a/packages/svelte/src/compiler/phases/3-transform/server/transform-server.js b/packages/svelte/src/compiler/phases/3-transform/server/transform-server.js index 0a533aec37..44690a1efe 100644 --- a/packages/svelte/src/compiler/phases/3-transform/server/transform-server.js +++ b/packages/svelte/src/compiler/phases/3-transform/server/transform-server.js @@ -210,14 +210,25 @@ export function server_component(analysis, options) { ]; } - if ( - [...analysis.instance.scope.declarations.values()].some( - (binding) => binding.kind === 'store_sub' - ) - ) { + const store_subs = [...analysis.instance.scope.declarations.values()].filter( + (binding) => binding.kind === 'store_sub' + ); + + // a blocked subscription is only created once its promise resolves, so its teardown must wait until the render is done + const defer_store_teardown = store_subs.some((binding) => binding.blocker); + + if (store_subs.length > 0) { instance.body.unshift(b.var('$$store_subs')); + + const unsubscribe = b.if( + b.id('$$store_subs'), + b.stmt(b.call('$.unsubscribe_stores', b.id('$$store_subs'))) + ); + template.body.push( - b.if(b.id('$$store_subs'), b.stmt(b.call('$.unsubscribe_stores', b.id('$$store_subs')))) + defer_store_teardown + ? b.stmt(b.call('$$renderer.on_destroy', b.arrow([], b.block([unsubscribe])))) + : unsubscribe ); } @@ -257,7 +268,7 @@ export function server_component(analysis, options) { ); } - let should_inject_context = dev || analysis.needs_context; + let should_inject_context = dev || analysis.needs_context || defer_store_teardown; if (should_inject_context) { component_block = b.block([ diff --git a/packages/svelte/tests/runtime-runes/samples/async-store-sub-blocker/_config.js b/packages/svelte/tests/runtime-runes/samples/async-store-sub-blocker/_config.js new file mode 100644 index 0000000000..896385e609 --- /dev/null +++ b/packages/svelte/tests/runtime-runes/samples/async-store-sub-blocker/_config.js @@ -0,0 +1,14 @@ +import { tick } from 'svelte'; +import { test } from '../../test'; + +// Tests that a store subscription only present in the template waits for the +// promise that assigns the store instead of subscribing to `undefined`, +// including when the subscription is read through a function. +export default test({ + mode: ['client', 'hydrate', 'async-server'], + ssrHtml: '

hello

hello

', + async test({ assert, target }) { + await tick(); + assert.htmlEqual(target.innerHTML, '

hello

hello

'); + } +}); diff --git a/packages/svelte/tests/runtime-runes/samples/async-store-sub-blocker/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-store-sub-blocker/main.svelte new file mode 100644 index 0000000000..04c707c66d --- /dev/null +++ b/packages/svelte/tests/runtime-runes/samples/async-store-sub-blocker/main.svelte @@ -0,0 +1,16 @@ + + +

{$store}

+

{read()}

diff --git a/packages/svelte/tests/runtime-runes/samples/async-store-sub-teardown/_config.js b/packages/svelte/tests/runtime-runes/samples/async-store-sub-teardown/_config.js new file mode 100644 index 0000000000..ac60694648 --- /dev/null +++ b/packages/svelte/tests/runtime-runes/samples/async-store-sub-teardown/_config.js @@ -0,0 +1,18 @@ +import { test } from '../../test'; +import { counts, reset } from './store.js'; + +// A blocked store subscription is created after the synchronous part of the +// render has finished, so the teardown must wait for the async work. +export default test({ + mode: ['async-server'], + + before_test() { + reset(); + }, + + ssrHtml: '

hello

', + + test_ssr({ assert }) { + assert.deepEqual(counts, { subscribes: 1, unsubscribes: 1 }); + } +}); diff --git a/packages/svelte/tests/runtime-runes/samples/async-store-sub-teardown/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-store-sub-teardown/main.svelte new file mode 100644 index 0000000000..8d17e701d3 --- /dev/null +++ b/packages/svelte/tests/runtime-runes/samples/async-store-sub-teardown/main.svelte @@ -0,0 +1,11 @@ + + +

{$s}

diff --git a/packages/svelte/tests/runtime-runes/samples/async-store-sub-teardown/store.js b/packages/svelte/tests/runtime-runes/samples/async-store-sub-teardown/store.js new file mode 100644 index 0000000000..4922c1b027 --- /dev/null +++ b/packages/svelte/tests/runtime-runes/samples/async-store-sub-teardown/store.js @@ -0,0 +1,23 @@ +import { writable } from 'svelte/store'; + +export const counts = { subscribes: 0, unsubscribes: 0 }; + +const inner = writable('hello'); + +export const store = { + /** @param {(value: string) => void} fn */ + subscribe(fn) { + counts.subscribes += 1; + const unsubscribe = inner.subscribe(fn); + + return () => { + counts.unsubscribes += 1; + unsubscribe(); + }; + } +}; + +export function reset() { + counts.subscribes = 0; + counts.unsubscribes = 0; +}