From dfc8462d9865578ad11b4b6b6771c2c06b489cc1 Mon Sep 17 00:00:00 2001
From: Rich-Harris <richard.a.harris@gmail.com>
Date: Wed, 4 Apr 2018 08:29:54 -0400
Subject: [PATCH] fail validation if bound <select> has dynamic multiple
 attribute - fixes #1270

---
 src/validate/html/validateElement.ts              | 15 ++++++++++++++-
 .../binding-select-multiple-dynamic/errors.json   | 12 ++++++++++++
 .../binding-select-multiple-dynamic/input.html    |  5 +++++
 3 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 test/validator/samples/binding-select-multiple-dynamic/errors.json
 create mode 100644 test/validator/samples/binding-select-multiple-dynamic/input.html

diff --git a/src/validate/html/validateElement.ts b/src/validate/html/validateElement.ts
index 3fcec9784b27..00c195a85cc1 100644
--- a/src/validate/html/validateElement.ts
+++ b/src/validate/html/validateElement.ts
@@ -102,7 +102,20 @@ export default function validateElement(
 					);
 				}
 
-				checkTypeAttribute(validator, node);
+				if (node.name === 'select') {
+					const attribute = node.attributes.find(
+						(attribute: Node) => attribute.name === 'multiple'
+					);
+
+					if (attribute && isDynamic(attribute)) {
+						validator.error(
+							`'multiple' attribute cannot be dynamic if select uses two-way binding`,
+							attribute
+						);
+					}
+				} else {
+					checkTypeAttribute(validator, node);
+				}
 			} else if (name === 'checked' || name === 'indeterminate') {
 				if (node.name !== 'input') {
 					validator.error(
diff --git a/test/validator/samples/binding-select-multiple-dynamic/errors.json b/test/validator/samples/binding-select-multiple-dynamic/errors.json
new file mode 100644
index 000000000000..f6c9f145afcd
--- /dev/null
+++ b/test/validator/samples/binding-select-multiple-dynamic/errors.json
@@ -0,0 +1,12 @@
+[{
+	"message": "'multiple' attribute cannot be dynamic if select uses two-way binding",
+	"loc": {
+		"line": 1,
+		"column": 19
+	},
+	"end": {
+		"line": 1,
+		"column": 28
+	},
+	"pos": 19
+}]
\ No newline at end of file
diff --git a/test/validator/samples/binding-select-multiple-dynamic/input.html b/test/validator/samples/binding-select-multiple-dynamic/input.html
new file mode 100644
index 000000000000..17e928c5628d
--- /dev/null
+++ b/test/validator/samples/binding-select-multiple-dynamic/input.html
@@ -0,0 +1,5 @@
+<select bind:value :multiple>
+	<option>1</option>
+	<option>2</option>
+	<option>3</option>
+</select>
\ No newline at end of file