From f64a661fa5a983475177cc8a23426641dec065d0 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Thu, 7 Feb 2019 11:11:14 -0500
Subject: [PATCH] better cyclical dependency detection - fixes #2055

---
 src/compile/Component.ts                        |  3 ++-
 .../reactive-values-non-cyclical/_config.js     | 17 +++++++++++++++++
 .../reactive-values-non-cyclical/main.html      | 13 +++++++++++++
 .../reactive-declaration-cyclical/errors.json   |  7 +++++++
 .../reactive-declaration-cyclical/input.html    |  7 +++++++
 5 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 test/runtime/samples/reactive-values-non-cyclical/_config.js
 create mode 100644 test/runtime/samples/reactive-values-non-cyclical/main.html
 create mode 100644 test/validator/samples/reactive-declaration-cyclical/errors.json
 create mode 100644 test/validator/samples/reactive-declaration-cyclical/input.html

diff --git a/src/compile/Component.ts b/src/compile/Component.ts
index 659cf972cc..fa980593a3 100644
--- a/src/compile/Component.ts
+++ b/src/compile/Component.ts
@@ -1002,7 +1002,8 @@ export default class Component {
 							const object = getObject(node);
 							const { name } = object;
 
-							if (name[0] === '$' || component.var_lookup.has(name)) {
+							const owner = scope.findOwner(name);
+							if ((!owner || owner === component.instance_scope) && (name[0] === '$' || component.var_lookup.has(name))) {
 								dependencies.add(name);
 							}
 
diff --git a/test/runtime/samples/reactive-values-non-cyclical/_config.js b/test/runtime/samples/reactive-values-non-cyclical/_config.js
new file mode 100644
index 0000000000..e134a669ee
--- /dev/null
+++ b/test/runtime/samples/reactive-values-non-cyclical/_config.js
@@ -0,0 +1,17 @@
+export default {
+	props: {
+		x: 42
+	},
+
+	html: `
+		<p>42 42</p>
+	`,
+
+	test({ assert, component, target }) {
+		component.x = 43;
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>43 43</p>
+		`);
+	}
+};
diff --git a/test/runtime/samples/reactive-values-non-cyclical/main.html b/test/runtime/samples/reactive-values-non-cyclical/main.html
new file mode 100644
index 0000000000..061a38857a
--- /dev/null
+++ b/test/runtime/samples/reactive-values-non-cyclical/main.html
@@ -0,0 +1,13 @@
+<script>
+	export let x;
+
+	let a;
+	let b;
+
+	$: a = b;
+	$: b = (function(a) {
+		return a;
+	}(x));
+</script>
+
+<p>{a} {b}</p>
\ No newline at end of file
diff --git a/test/validator/samples/reactive-declaration-cyclical/errors.json b/test/validator/samples/reactive-declaration-cyclical/errors.json
new file mode 100644
index 0000000000..1e4169a0ee
--- /dev/null
+++ b/test/validator/samples/reactive-declaration-cyclical/errors.json
@@ -0,0 +1,7 @@
+[{
+	"message": "Cyclical dependency detected",
+	"code": "cyclical-reactive-declaration",
+	"start": { "line": 5, "column": 1, "character": 35 },
+	"end": { "line": 5, "column": 14, "character": 48 },
+	"pos": 35
+}]
\ No newline at end of file
diff --git a/test/validator/samples/reactive-declaration-cyclical/input.html b/test/validator/samples/reactive-declaration-cyclical/input.html
new file mode 100644
index 0000000000..c8221b9aa8
--- /dev/null
+++ b/test/validator/samples/reactive-declaration-cyclical/input.html
@@ -0,0 +1,7 @@
+<script>
+	let a = 1;
+	let b = 2;
+
+	$: a = b + 1;
+	$: b = a + 1;
+</script>
\ No newline at end of file