From 7b15ff93acfa7b572fc8476791ad0ab86dc060f3 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Wed, 30 Nov 2016 16:38:17 -0500
Subject: [PATCH] handle empty attributes in elements and components. fixes #63

---
 .../visitors/attributes/addComponentAttributes.js    |  7 +++++++
 .../visitors/attributes/addElementAttributes.js      | 12 ++++++++++++
 test/compiler/attribute-empty/_config.js             |  3 +++
 test/compiler/attribute-empty/main.html              |  1 +
 test/compiler/component-data-empty/Widget.html       |  1 +
 test/compiler/component-data-empty/_config.js        |  3 +++
 test/compiler/component-data-empty/main.html         | 11 +++++++++++
 7 files changed, 38 insertions(+)
 create mode 100644 test/compiler/attribute-empty/_config.js
 create mode 100644 test/compiler/attribute-empty/main.html
 create mode 100644 test/compiler/component-data-empty/Widget.html
 create mode 100644 test/compiler/component-data-empty/_config.js
 create mode 100644 test/compiler/component-data-empty/main.html

diff --git a/compiler/generate/visitors/attributes/addComponentAttributes.js b/compiler/generate/visitors/attributes/addComponentAttributes.js
index 9f002cd6c4..9995352dc8 100644
--- a/compiler/generate/visitors/attributes/addComponentAttributes.js
+++ b/compiler/generate/visitors/attributes/addComponentAttributes.js
@@ -16,6 +16,13 @@ export default function addComponentAttributes ( generator, node, local ) {
 				});
 			}
 
+			else if ( attribute.value.length === 0 ) {
+				local.staticAttributes.push({
+					name: attribute.name,
+					value: `''`
+				});
+			}
+
 			else if ( attribute.value.length === 1 ) {
 				const value = attribute.value[0];
 
diff --git a/compiler/generate/visitors/attributes/addElementAttributes.js b/compiler/generate/visitors/attributes/addElementAttributes.js
index b7aa5c4056..cb81a9a1f6 100644
--- a/compiler/generate/visitors/attributes/addElementAttributes.js
+++ b/compiler/generate/visitors/attributes/addElementAttributes.js
@@ -31,6 +31,18 @@ export default function addElementAttributes ( generator, node, local ) {
 				}
 			}
 
+			else if ( attribute.value.length === 0 ) {
+				if ( propertyName ) {
+					local.init.push( deindent`
+						${local.name}.${propertyName} = '';
+					` );
+				} else {
+					local.init.push( deindent`
+						${local.name}.setAttribute( '${attribute.name}', '' );
+					` );
+				}
+			}
+
 			else if ( attribute.value.length === 1 ) {
 				const value = attribute.value[0];
 
diff --git a/test/compiler/attribute-empty/_config.js b/test/compiler/attribute-empty/_config.js
new file mode 100644
index 0000000000..b9ce14cce1
--- /dev/null
+++ b/test/compiler/attribute-empty/_config.js
@@ -0,0 +1,3 @@
+export default {
+	html: `<div class=""></div>`
+};
diff --git a/test/compiler/attribute-empty/main.html b/test/compiler/attribute-empty/main.html
new file mode 100644
index 0000000000..7c7b3d103a
--- /dev/null
+++ b/test/compiler/attribute-empty/main.html
@@ -0,0 +1 @@
+<div class=''></div>
diff --git a/test/compiler/component-data-empty/Widget.html b/test/compiler/component-data-empty/Widget.html
new file mode 100644
index 0000000000..89d0010a35
--- /dev/null
+++ b/test/compiler/component-data-empty/Widget.html
@@ -0,0 +1 @@
+<p>foo: '{{foo}}'</p>
diff --git a/test/compiler/component-data-empty/_config.js b/test/compiler/component-data-empty/_config.js
new file mode 100644
index 0000000000..eaf16a72af
--- /dev/null
+++ b/test/compiler/component-data-empty/_config.js
@@ -0,0 +1,3 @@
+export default {
+	html: `<div><p>foo: ''</p></div>`
+};
diff --git a/test/compiler/component-data-empty/main.html b/test/compiler/component-data-empty/main.html
new file mode 100644
index 0000000000..8b797c8a60
--- /dev/null
+++ b/test/compiler/component-data-empty/main.html
@@ -0,0 +1,11 @@
+<div>
+	<Widget foo=''/>
+</div>
+
+<script>
+	import Widget from './Widget.html';
+
+	export default {
+		components: { Widget }
+	};
+</script>