From e1a783171104c6487a6627a73581060c3fa381cc Mon Sep 17 00:00:00 2001
From: tanhauhau <lhtan93@gmail.com>
Date: Sun, 17 Jul 2022 23:46:44 +0800
Subject: [PATCH] set auto-subscription to undefined when update store to falsy
 value

---
 src/compiler/compile/render_dom/index.ts            |  2 +-
 src/runtime/internal/utils.ts                       |  9 +++++++++
 test/runtime/samples/store-resubscribe-d/_config.js | 13 +++++++++++++
 .../runtime/samples/store-resubscribe-d/main.svelte |  6 ++++++
 4 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 test/runtime/samples/store-resubscribe-d/_config.js
 create mode 100644 test/runtime/samples/store-resubscribe-d/main.svelte

diff --git a/src/compiler/compile/render_dom/index.ts b/src/compiler/compile/render_dom/index.ts
index 5fdac9bce4..ff3dbffbf8 100644
--- a/src/compiler/compile/render_dom/index.ts
+++ b/src/compiler/compile/render_dom/index.ts
@@ -434,7 +434,7 @@ export default function dom(
 				const subscribe = `$$subscribe_${name}`;
 				const i = renderer.context_lookup.get($name).index;
 
-				return b`let ${$name}, ${unsubscribe} = @noop, ${subscribe} = () => (${unsubscribe}(), ${unsubscribe} = @subscribe(${name}, $$value => $$invalidate(${i}, ${$name} = $$value)), ${name})`;
+				return b`let ${$name}, ${unsubscribe} = @noop, ${subscribe} = () => (${unsubscribe}(), ${unsubscribe} = @subscribe_dynamic_store(${name}, $$value => $$invalidate(${i}, ${$name} = $$value)), ${name})`;
 			}
 
 			return b`let ${$name};`;
diff --git a/src/runtime/internal/utils.ts b/src/runtime/internal/utils.ts
index 8868e38ee2..83369bbf33 100644
--- a/src/runtime/internal/utils.ts
+++ b/src/runtime/internal/utils.ts
@@ -72,6 +72,15 @@ export function subscribe(store, ...callbacks) {
 	return unsub.unsubscribe ? () => unsub.unsubscribe() : unsub;
 }
 
+export function subscribe_dynamic_store(store, callback) {
+	if (store == null) {
+		callback(undefined);
+		return noop;
+	}
+	const unsub = store.subscribe(callback);
+	return unsub.unsubscribe ? () => unsub.unsubscribe() : unsub;
+}
+
 export function get_store_value<T>(store: Readable<T>): T {
 	let value;
 	subscribe(store, _ => value = _)();
diff --git a/test/runtime/samples/store-resubscribe-d/_config.js b/test/runtime/samples/store-resubscribe-d/_config.js
new file mode 100644
index 0000000000..14337d7b75
--- /dev/null
+++ b/test/runtime/samples/store-resubscribe-d/_config.js
@@ -0,0 +1,13 @@
+import { writable } from 'svelte/store';
+
+export default {
+	html: '31',
+	async test({ assert, component, target, window }) {
+		component.store = undefined;
+
+		assert.htmlEqual(target.innerHTML, 'undefined');
+		
+		component.store = writable(42);
+		assert.htmlEqual(target.innerHTML, '42');
+	}
+};
diff --git a/test/runtime/samples/store-resubscribe-d/main.svelte b/test/runtime/samples/store-resubscribe-d/main.svelte
new file mode 100644
index 0000000000..a6319c485d
--- /dev/null
+++ b/test/runtime/samples/store-resubscribe-d/main.svelte
@@ -0,0 +1,6 @@
+<script>
+	import { writable } from 'svelte/store';
+	export let store = writable(31);
+</script>
+
+{$store}