From a6c5ee33fc0747751a5e9c67964d139664b1a79b Mon Sep 17 00:00:00 2001
From: Tan Li Hau <lhtan93@gmail.com>
Date: Wed, 28 Oct 2020 08:08:44 +0800
Subject: [PATCH] reactive dependency not referenced can't set to undefined
 initially

---
 src/compiler/compile/render_dom/Renderer.ts   |  7 ++---
 .../expected.js                               |  2 +-
 .../expected.js                               |  6 ++---
 .../expected.js                               |  2 +-
 .../_config.js                                | 26 +++++++++++++++++++
 .../main.svelte                               | 19 ++++++++++++++
 6 files changed, 54 insertions(+), 8 deletions(-)
 create mode 100644 test/runtime/samples/reactive-value-dependency-not-referenced/_config.js
 create mode 100644 test/runtime/samples/reactive-value-dependency-not-referenced/main.svelte

diff --git a/src/compiler/compile/render_dom/Renderer.ts b/src/compiler/compile/render_dom/Renderer.ts
index fb04be1574..7db8cf645b 100644
--- a/src/compiler/compile/render_dom/Renderer.ts
+++ b/src/compiler/compile/render_dom/Renderer.ts
@@ -111,8 +111,9 @@ export default class Renderer {
 
 				// these determine whether variable is included in initial context
 				// array, so must have the highest priority
-				if (variable.export_name) member.priority += 16;
-				if (variable.referenced) member.priority += 32;
+				if (variable.is_reactive_dependency && (variable.mutated || variable.reassigned)) member.priority += 16;
+				if (variable.export_name) member.priority += 32;
+				if (variable.referenced) member.priority += 64;
 			} else if (member.is_non_contextual) {
 				// determine whether variable is included in initial context
 				// array, so must have the highest priority
@@ -131,7 +132,7 @@ export default class Renderer {
 		while (i--) {
 			const member = this.context[i];
 			if (member.variable) {
-				if (member.variable.referenced || member.variable.export_name) break;
+				if (member.variable.referenced || member.variable.export_name || (member.variable.is_reactive_dependency && (member.variable.mutated || member.variable.reassigned))) break;
 			} else if (member.is_non_contextual) {
 				break;
 			}
diff --git a/test/js/samples/instrumentation-script-main-block/expected.js b/test/js/samples/instrumentation-script-main-block/expected.js
index bc80924602..a471a50b37 100644
--- a/test/js/samples/instrumentation-script-main-block/expected.js
+++ b/test/js/samples/instrumentation-script-main-block/expected.js
@@ -62,7 +62,7 @@ function instance($$self, $$props, $$invalidate) {
 		}
 	};
 
-	return [x];
+	return [x, y];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/reactive-values-non-topologically-ordered/expected.js b/test/js/samples/reactive-values-non-topologically-ordered/expected.js
index 15290496d5..dbfd794dc7 100644
--- a/test/js/samples/reactive-values-non-topologically-ordered/expected.js
+++ b/test/js/samples/reactive-values-non-topologically-ordered/expected.js
@@ -12,15 +12,15 @@ function instance($$self, $$props, $$invalidate) {
 
 	$$self.$$.update = () => {
 		if ($$self.$$.dirty & /*x*/ 1) {
-			$: $$invalidate(2, b = x);
+			$: $$invalidate(1, b = x);
 		}
 
-		if ($$self.$$.dirty & /*b*/ 4) {
+		if ($$self.$$.dirty & /*b*/ 2) {
 			$: a = b;
 		}
 	};
 
-	return [x];
+	return [x, b];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/unreferenced-state-not-invalidated/expected.js b/test/js/samples/unreferenced-state-not-invalidated/expected.js
index b10ea815b9..599d18f114 100644
--- a/test/js/samples/unreferenced-state-not-invalidated/expected.js
+++ b/test/js/samples/unreferenced-state-not-invalidated/expected.js
@@ -64,7 +64,7 @@ function instance($$self, $$props, $$invalidate) {
 	};
 
 	$: x = a * 2;
-	return [y];
+	return [y, b];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/runtime/samples/reactive-value-dependency-not-referenced/_config.js b/test/runtime/samples/reactive-value-dependency-not-referenced/_config.js
new file mode 100644
index 0000000000..893b183d78
--- /dev/null
+++ b/test/runtime/samples/reactive-value-dependency-not-referenced/_config.js
@@ -0,0 +1,26 @@
+export default {
+	html: `
+		<p>42</p>
+		<p>42</p>
+	`,
+
+	async test({ assert, component, target }) {
+		await component.updateStore(undefined);
+		assert.htmlEqual(target.innerHTML, '<p>undefined</p><p>42</p>');
+
+		await component.updateStore(33);
+		assert.htmlEqual(target.innerHTML, '<p>33</p><p>42</p>');
+
+		await component.updateStore(undefined);
+		assert.htmlEqual(target.innerHTML, '<p>undefined</p><p>42</p>');
+
+		await component.updateVar(undefined);
+		assert.htmlEqual(target.innerHTML, '<p>undefined</p><p>undefined</p>');
+
+		await component.updateVar(33);
+		assert.htmlEqual(target.innerHTML, '<p>undefined</p><p>33</p>');
+
+		await component.updateVar(undefined);
+		assert.htmlEqual(target.innerHTML, '<p>undefined</p><p>undefined</p>');
+	}
+};
diff --git a/test/runtime/samples/reactive-value-dependency-not-referenced/main.svelte b/test/runtime/samples/reactive-value-dependency-not-referenced/main.svelte
new file mode 100644
index 0000000000..57e6ba84f3
--- /dev/null
+++ b/test/runtime/samples/reactive-value-dependency-not-referenced/main.svelte
@@ -0,0 +1,19 @@
+<script>
+	import { writable } from 'svelte/store';
+	let store = writable(42);
+	let variable = 42;
+	let value;
+	let value2;
+	$: value = $store;
+	$: value2 = variable;
+
+	export function updateStore(value) {
+		store.set(value);
+	}
+	export function updateVar(value) {
+		variable = value;
+	}
+</script>
+
+<p>{ value }</p>
+<p>{ value2 }</p>
\ No newline at end of file