From 138213ca3c1ca91998461e961933d630aeb45b15 Mon Sep 17 00:00:00 2001
From: Conduitry <git@chor.date>
Date: Sun, 23 Feb 2020 16:35:25 -0500
Subject: [PATCH] fix dev mode each block validation when using strings (#4451)

---
 CHANGELOG.md                                       |  4 ++++
 src/runtime/internal/dev.ts                        |  2 +-
 test/runtime/samples/each-block-string/_config.js  | 10 ++++++++++
 test/runtime/samples/each-block-string/main.svelte |  3 +++
 4 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 test/runtime/samples/each-block-string/_config.js
 create mode 100644 test/runtime/samples/each-block-string/main.svelte

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f81b19815480..3f4460cde48e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Svelte changelog
 
+## Unreleased
+
+* Fix dev mode validation of `{#each}` blocks using strings ([#4450](https://github.com/sveltejs/svelte/issues/4450))
+
 ## 3.19.0
 
 * Fix indirect bindings involving elements with spreads ([#3680](https://github.com/sveltejs/svelte/issues/3680))
diff --git a/src/runtime/internal/dev.ts b/src/runtime/internal/dev.ts
index 2d60ffb98529..8aefc88ba7b0 100644
--- a/src/runtime/internal/dev.ts
+++ b/src/runtime/internal/dev.ts
@@ -80,7 +80,7 @@ export function set_data_dev(text, data) {
 }
 
 export function validate_each_argument(arg) {
-	if (!arg || !('length' in arg)) {
+	if (typeof arg !== 'string' && !(arg && typeof arg === 'object' && 'length' in arg)) {
 		let msg = '{#each} only iterates over array-like objects.';
 		if (typeof Symbol === 'function' && arg && Symbol.iterator in arg) {
 			msg += ' You can use a spread to convert this iterable into an array.';
diff --git a/test/runtime/samples/each-block-string/_config.js b/test/runtime/samples/each-block-string/_config.js
new file mode 100644
index 000000000000..7366c964ebb1
--- /dev/null
+++ b/test/runtime/samples/each-block-string/_config.js
@@ -0,0 +1,10 @@
+export default {
+	compileOptions: {
+		dev: true
+	},
+	html: `
+		<div>f</div>
+		<div>o</div>
+		<div>o</div>
+	`
+};
diff --git a/test/runtime/samples/each-block-string/main.svelte b/test/runtime/samples/each-block-string/main.svelte
new file mode 100644
index 000000000000..ae60f0f6b32f
--- /dev/null
+++ b/test/runtime/samples/each-block-string/main.svelte
@@ -0,0 +1,3 @@
+{#each 'foo' as c}
+	<div>{c}</div>
+{/each}