Fix each blocks not unmounting components correctly (#3056)

* Prevent outro from invoking detach multiple times

* Add tests for unmounting entries in an each block

* Remove redundant function for removing from lookup

src/runtime/internal/keyed-each.ts

@@ -7,7 +7,7 @@ export function destroy_block(block, lookup) {
 
 export function outro_and_destroy_block(block, lookup) {
 	transition_out(block, 1, () => {
-		destroy_block(block, lookup);
+		lookup.delete(block.key);
 	});
 }
 

test/runtime/samples/each-block-keyed-shift/Nested.svelte

@@ -0,0 +1,5 @@
+<script>
+	export let title;
+</script>
+
+<p>{title}</p>

test/runtime/samples/each-block-keyed-shift/_config.js

@@ -0,0 +1,27 @@
+export default {
+	props: {
+		titles: [{ name: 'a', }, { name: 'b' }, { name: 'c' }]
+	},
+
+	html: `
+		<p>a</p>
+		<p>b</p>
+		<p>c</p>
+	`,
+
+	test({ assert, component, target }) {
+		component.titles = [{ name: 'b' }, { name: 'c' }];
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>b</p>
+			<p>c</p>
+		`);
+
+		component.titles = [{ name: 'c' }];
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>c</p>
+		`);
+
+	}
+};

test/runtime/samples/each-block-keyed-shift/main.svelte

@@ -0,0 +1,9 @@
+<script>
+	import Nested from './Nested.svelte';
+
+	export let titles;
+</script>
+
+{#each titles as title (title.name)}
+	<Nested title="{title.name}"/>
+{/each}