Fix rendering of static boolean attributes

compiler/ElementNode.js

@@ -224,6 +224,9 @@ ElementNode.prototype = {
             }
             if (attr.value === null || attr.value === undefined) {
                 template.text(' ' + name);
+            } else if (attr.value === '') {
+                // Treat empty attributes as boolean attributes
+                template.text(' ' + name);
             } else if (template.isExpression(attr.value)) {
                 template.attr(name, attr.value, attr.escapeXml !== false);
             } else {

test/render-test.js

@@ -356,4 +356,18 @@ describe('marko/marko' , function() {
             url: '/foo'
         }, done);
     });
+
+    it("should support boolean attributes", function(done) {
+        testRender("test-project/html-templates/boolean-attributes.marko", {
+            options: [
+                {  value: 'red', selected: false },
+                {  value: 'green', selected: true },
+                {  value: 'blue', selected: false }
+            ],
+            disabled: false,
+            checked: true
+        }, done);
+    });
+
+
 });

test/test-project/html-templates/boolean-attributes.marko

@@ -0,0 +1,13 @@
+<input type="checkbox" checked="${data.checked}">
+
+<button disabled>Button</button>
+
+<select>
+    <option value="${option.value}"
+        selected="${option.selected}"
+        for="option in data.options">
+
+        ${option.value}
+
+    </option>
+</select>

test/test-project/html-templates/boolean-attributes.marko.expected.html

@@ -0,0 +1 @@
+<input type="checkbox" checked><button disabled>Button</button><select><option value="red">red</option><option value="green" selected>green</option><option value="blue">blue</option></select>

test/test-project/html-templates/simple-conditionals.marko

@@ -8,6 +8,6 @@
 
 <span class="{?count;under\;-50\\;over-50}"></span>
 
-<input type="checked" checked="{?true}"/>
+<input type="checked" checked="{?true;${true}}"/>
 
 {?count>50;{?name;Hello $name! }Over 50;{?name;Hello $name! }50 or less}

test/test-project/xml-templates/simple-conditionals.marko.xml

@@ -1,14 +1,14 @@
-<template 
+<template
     params="name,count">
     <div class="{?count>50;over-50}"></div>
     <div class="{?count lt 50;under-50}"></div>
     <div class="{?count lt 50;under-50;over-50}"></div>
     <div class="{?count lt 50;under-50;#}"></div>
-    
+
     <span class="{?count;under\;-50\\;over-50}"></span>
 
-    <input type="checked" checked="{?true}"/>
-    
+    <input type="checked" checked="{?true;${true}}"/>
+
     {?count>50;{?name;Hello $name! }Over 50;{?name;Hello $name! }50 or less}
-    
+
 </template>