From 47f9c3dbfdfcbb978522da04a50bc50fa1762508 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Fri, 23 Jun 2017 17:56:34 -0400
Subject: [PATCH] dont recreate if_blocks incorrectly

---
 src/generators/dom/visitors/IfBlock.ts        |  7 +++-
 .../_config.js                                | 37 +++++++++++++++++++
 .../main.html                                 | 26 +++++++++++++
 3 files changed, 68 insertions(+), 2 deletions(-)
 create mode 100644 test/runtime/samples/transition-js-if-block-in-each-block-bidi-3/_config.js
 create mode 100644 test/runtime/samples/transition-js-if-block-in-each-block-bidi-3/main.html

diff --git a/src/generators/dom/visitors/IfBlock.ts b/src/generators/dom/visitors/IfBlock.ts
index e7fecebefece..fc2c54ca9738 100644
--- a/src/generators/dom/visitors/IfBlock.ts
+++ b/src/generators/dom/visitors/IfBlock.ts
@@ -369,8 +369,11 @@ function compoundWithOutros(
 	`;
 
 	const createNewBlock = deindent`
-		${name} = ${if_blocks}[ ${current_block_index} ] = ${if_block_creators}[ ${current_block_index} ]( ${params}, ${block.component} );
-		${name}.create();
+		${name} = ${if_blocks}[ ${current_block_index} ];
+		if ( !${name} ) {
+			${name} = ${if_blocks}[ ${current_block_index} ] = ${if_block_creators}[ ${current_block_index} ]( ${params}, ${block.component} );
+			${name}.create();
+		}
 		${name}.${mountOrIntro}( ${parentNode}, ${anchor} );
 	`;
 
diff --git a/test/runtime/samples/transition-js-if-block-in-each-block-bidi-3/_config.js b/test/runtime/samples/transition-js-if-block-in-each-block-bidi-3/_config.js
new file mode 100644
index 000000000000..bcb5a9e05f68
--- /dev/null
+++ b/test/runtime/samples/transition-js-if-block-in-each-block-bidi-3/_config.js
@@ -0,0 +1,37 @@
+export default {
+	data: {
+		foo: false,
+		threshold: 5
+	},
+
+	html: `
+		<div>1</div>
+		<div>2</div>
+		<div>3</div>
+		<div>4</div>
+		<div>5</div>
+	`,
+
+	test ( assert, component, target, window, raf ) {
+		const divs = target.querySelectorAll('div');
+
+		raf.tick(100);
+
+		component.set({ threshold: 4 });
+		raf.tick(150);
+		component.set({ threshold: 5 });
+		raf.tick(200);
+
+		component.set({ threshold: 5.5 });
+
+		assert.htmlEqual(target.innerHTML, `
+			<div>1</div>
+			<div>2</div>
+			<div>3</div>
+			<div>4</div>
+			<div>5</div>
+		`);
+
+		component.destroy();
+	}
+};
\ No newline at end of file
diff --git a/test/runtime/samples/transition-js-if-block-in-each-block-bidi-3/main.html b/test/runtime/samples/transition-js-if-block-in-each-block-bidi-3/main.html
new file mode 100644
index 000000000000..d68c95e8b038
--- /dev/null
+++ b/test/runtime/samples/transition-js-if-block-in-each-block-bidi-3/main.html
@@ -0,0 +1,26 @@
+{{#each [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] as number}}
+	{{#if foo}}
+		{{#if threshold >= number}}
+			<div transition:foo>{{number}}</div>
+		{{/if}}
+	{{else}}
+		{{#if threshold >= number}}
+			<div transition:foo>{{number}}</div>
+		{{/if}}
+	{{/if}}
+{{/each}}
+
+<script>
+	export default {
+		transitions: {
+			foo: function ( node ) {
+				return {
+					duration: 100,
+					tick: t => {
+						node.foo = t;
+					}
+				};
+			}
+		}
+	};
+</script>
\ No newline at end of file