From 43666109467066a4c9f12fbeaf8f06131e37dce1 Mon Sep 17 00:00:00 2001
From: Tan Li Hau <lhtan93@gmail.com>
Date: Thu, 20 Aug 2020 00:38:40 +0800
Subject: [PATCH] handle undefined input value with spread

---
 .../compile/render_dom/wrappers/Element/index.ts     |  9 +++++++++
 .../spread-element-input-value-undefined/_config.js  | 12 ++++++++++++
 .../spread-element-input-value-undefined/main.svelte |  5 +++++
 3 files changed, 26 insertions(+)
 create mode 100644 test/runtime/samples/spread-element-input-value-undefined/_config.js
 create mode 100644 test/runtime/samples/spread-element-input-value-undefined/main.svelte

diff --git a/src/compiler/compile/render_dom/wrappers/Element/index.ts b/src/compiler/compile/render_dom/wrappers/Element/index.ts
index f11ce63023..695f41d344 100644
--- a/src/compiler/compile/render_dom/wrappers/Element/index.ts
+++ b/src/compiler/compile/render_dom/wrappers/Element/index.ts
@@ -725,6 +725,15 @@ export default class ElementWrapper extends Wrapper {
 			block.chunks.update.push(b`
 				if (${block.renderer.dirty(Array.from(dependencies))} && ${data}.multiple) @select_options(${this.var}, ${data}.value);
 			`);
+		} else if (this.node.name === 'input' && this.attributes.find(attr => attr.node.name === 'value')) {
+			block.chunks.mount.push(b`
+				${this.var}.value = ${data}.value;
+			`);
+			block.chunks.update.push(b`
+				if ('value' in ${data}) {
+					${this.var}.value = ${data}.value;
+				}
+			`);
 		}
 	}
 
diff --git a/test/runtime/samples/spread-element-input-value-undefined/_config.js b/test/runtime/samples/spread-element-input-value-undefined/_config.js
new file mode 100644
index 0000000000..1459462e07
--- /dev/null
+++ b/test/runtime/samples/spread-element-input-value-undefined/_config.js
@@ -0,0 +1,12 @@
+export default {
+	async test({ assert, component, target, window }) {
+		const input = target.querySelector("input");
+		component.value = undefined;
+
+		assert.equal(input.value, "undefined");
+
+		component.value = "foobar";
+
+		assert.equal(input.value, "foobar");
+	},
+};
diff --git a/test/runtime/samples/spread-element-input-value-undefined/main.svelte b/test/runtime/samples/spread-element-input-value-undefined/main.svelte
new file mode 100644
index 0000000000..5c9121dc03
--- /dev/null
+++ b/test/runtime/samples/spread-element-input-value-undefined/main.svelte
@@ -0,0 +1,5 @@
+<script>
+	export let value = '';
+</script>
+
+<input {value} {...{}} />
\ No newline at end of file