fix: insert comment before text in an each block, to prevent glued nodes (#13073)

Author: Rich-Harris

.changeset/orange-sheep-exist.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: insert comment before text in an each block, to prevent glued nodes

packages/svelte/src/compiler/phases/3-transform/utils.js

@@ -287,10 +287,11 @@ export function clean_nodes(
 					!first.attributes.some(
 						(attribute) => attribute.type === 'Attribute' && attribute.name.startsWith('--')
 					))),
-		/** if a component or snippet starts with text, we need to add an anchor comment so that its text node doesn't get fused with its surroundings */
+		/** if a component/snippet/each block starts with text, we need to add an anchor comment so that its text node doesn't get fused with its surroundings */
 		is_text_first:
 			(parent.type === 'Fragment' ||
 				parent.type === 'SnippetBlock' ||
+				parent.type === 'EachBlock' ||
 				parent.type === 'SvelteComponent' ||
 				parent.type === 'Component' ||
 				parent.type === 'SvelteSelf') &&

packages/svelte/tests/hydration/samples/each-preserve-whitespace/main.svelte

@@ -0,0 +1,5 @@
+<svelte:options preserveWhitespace />
+
+{#each 'abc' as l}
+	<div>{l}</div>
+{/each}

packages/svelte/tests/hydration/samples/each-text-only/main.svelte

@@ -0,0 +1,3 @@
+{#each 'abc' as l}
+	{l}
+{/each}

packages/svelte/tests/snapshot/samples/each-string-template/_expected/client/index.svelte.js

@@ -6,6 +6,8 @@ export default function Each_string_template($$anchor) {
 	var node = $.first_child(fragment);
 
 	$.each(node, 0, () => ['foo', 'bar', 'baz'], $.index, ($$anchor, thing) => {
+		$.next();
+
 		var text = $.text();
 
 		$.template_effect(() => $.set_text(text, `${thing ?? ""}, `));

packages/svelte/tests/snapshot/samples/each-string-template/_expected/server/index.svelte.js

@@ -8,7 +8,7 @@ export default function Each_string_template($$payload) {
 	for (let $$index = 0, $$length = each_array.length; $$index < $$length; $$index++) {
 		const thing = each_array[$$index];
 
-		$$payload.out += `${$.escape(thing)}, `;
+		$$payload.out += `<!---->${$.escape(thing)}, `;
 	}
 
 	$$payload.out += `<!--]-->`;