From b2ea03dde036fa73a863419ea44ec8ab4381ecf0 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Sat, 27 May 2017 12:29:44 -0400
Subject: [PATCH] prevent textarea from having both value and children

---
 src/validate/html/validateElement.ts                      | 8 ++++++++
 .../validator/samples/textarea-value-children/errors.json | 8 ++++++++
 test/validator/samples/textarea-value-children/input.html | 3 +++
 3 files changed, 19 insertions(+)
 create mode 100644 test/validator/samples/textarea-value-children/errors.json
 create mode 100644 test/validator/samples/textarea-value-children/input.html

diff --git a/src/validate/html/validateElement.ts b/src/validate/html/validateElement.ts
index 6610e7ee69..18c906b298 100644
--- a/src/validate/html/validateElement.ts
+++ b/src/validate/html/validateElement.ts
@@ -77,6 +77,14 @@ export default function validateElement ( validator: Validator, node: Node ) {
 				validator.error( `Missing transition '${attribute.name}'`, attribute.start );
 			}
 		}
+
+		else if ( attribute.type === 'Attribute' ) {
+			if ( attribute.name === 'value' && node.name === 'textarea' ) {
+				if ( node.children.length ) {
+					validator.error( `A <textarea> can have either a value attribute or (equivalently) child content, but not both`, attribute.start );
+				}
+			}
+		}
 	});
 }
 
diff --git a/test/validator/samples/textarea-value-children/errors.json b/test/validator/samples/textarea-value-children/errors.json
new file mode 100644
index 0000000000..21282fb93b
--- /dev/null
+++ b/test/validator/samples/textarea-value-children/errors.json
@@ -0,0 +1,8 @@
+[{
+	"message": "A <textarea> can have either a value attribute or (equivalently) child content, but not both",
+	"loc": {
+		"line": 1,
+		"column": 10
+	},
+	"pos": 10
+}]
\ No newline at end of file
diff --git a/test/validator/samples/textarea-value-children/input.html b/test/validator/samples/textarea-value-children/input.html
new file mode 100644
index 0000000000..70ba6d5a1f
--- /dev/null
+++ b/test/validator/samples/textarea-value-children/input.html
@@ -0,0 +1,3 @@
+<textarea value='{{foo}}'>
+	some illegal text
+</textarea>
\ No newline at end of file