Download attribute

src/browser/ui/dom/DOMProperty.js

@@ -34,6 +34,7 @@ var DOMPropertyInjection = {
   HAS_BOOLEAN_VALUE: 0x8,
   HAS_NUMERIC_VALUE: 0x10,
   HAS_POSITIVE_NUMERIC_VALUE: 0x20 | 0x10,
+  HAS_OVERLOADED_BOOLEAN_VALUE: 0x40,
 
   /**
    * Inject some specialized knowledge about the DOM. This takes a config object
@@ -115,6 +116,8 @@ var DOMPropertyInjection = {
         propConfig & DOMPropertyInjection.HAS_NUMERIC_VALUE;
       DOMProperty.hasPositiveNumericValue[propName] =
         propConfig & DOMPropertyInjection.HAS_POSITIVE_NUMERIC_VALUE;
+      DOMProperty.hasOverloadedBooleanValue[propName] =
+        propConfig & DOMPropertyInjection.HAS_OVERLOADED_BOOLEAN_VALUE;
 
       invariant(
         !DOMProperty.mustUseAttribute[propName] ||
@@ -129,9 +132,11 @@ var DOMPropertyInjection = {
         propName
       );
       invariant(
-        !DOMProperty.hasBooleanValue[propName] ||
-          !DOMProperty.hasNumericValue[propName],
-        'DOMProperty: Cannot have both boolean and numeric value: %s',
+        !!DOMProperty.hasBooleanValue[propName] +
+          !!DOMProperty.hasNumericValue[propName] +
+          !!DOMProperty.hasOverloadedBooleanValue[propName] <= 1,
+        'DOMProperty: Value can be one of boolean, overloaded boolean, or ' +
+        'numeric value, but not a combination: %s',
         propName
       );
     }
@@ -231,6 +236,14 @@ var DOMProperty = {
    */
   hasPositiveNumericValue: {},
 
+  /**
+   * Whether the property can be used as a flag as well as with a value. Removed
+   * when strictly equal to false; present without a value when strictly equal
+   * to true; present with a value otherwise.
+   * @type {Object}
+   */
+  hasOverloadedBooleanValue: {},
+
   /**
    * All of the isCustomAttribute() functions that have been injected.
    */

src/browser/ui/dom/DOMPropertyOperations.js

@@ -29,7 +29,8 @@ function shouldIgnoreValue(name, value) {
   return value == null ||
     (DOMProperty.hasBooleanValue[name] && !value) ||
     (DOMProperty.hasNumericValue[name] && isNaN(value)) ||
-    (DOMProperty.hasPositiveNumericValue[name] && (value < 1));
+    (DOMProperty.hasPositiveNumericValue[name] && (value < 1)) ||
+    (DOMProperty.hasOverloadedBooleanValue[name] && value === false);
 }
 
 var processAttributeNameAndPrefix = memoizeStringOnly(function(name) {
@@ -96,7 +97,8 @@ var DOMPropertyOperations = {
         return '';
       }
       var attributeName = DOMProperty.getAttributeName[name];
-      if (DOMProperty.hasBooleanValue[name]) {
+      if (DOMProperty.hasBooleanValue[name] ||
+          (DOMProperty.hasOverloadedBooleanValue[name] && value === true)) {
         return escapeTextForBrowser(attributeName);
       }
       return processAttributeNameAndPrefix(attributeName) +

src/browser/ui/dom/DefaultDOMPropertyConfig.js

@@ -29,6 +29,8 @@ var HAS_SIDE_EFFECTS = DOMProperty.injection.HAS_SIDE_EFFECTS;
 var HAS_NUMERIC_VALUE = DOMProperty.injection.HAS_NUMERIC_VALUE;
 var HAS_POSITIVE_NUMERIC_VALUE =
   DOMProperty.injection.HAS_POSITIVE_NUMERIC_VALUE;
+var HAS_OVERLOADED_BOOLEAN_VALUE =
+  DOMProperty.injection.HAS_OVERLOADED_BOOLEAN_VALUE;
 
 var DefaultDOMPropertyConfig = {
   isCustomAttribute: RegExp.prototype.test.bind(
@@ -66,7 +68,7 @@ var DefaultDOMPropertyConfig = {
     defer: HAS_BOOLEAN_VALUE,
     dir: null,
     disabled: MUST_USE_ATTRIBUTE | HAS_BOOLEAN_VALUE,
-    download: null,
+    download: HAS_OVERLOADED_BOOLEAN_VALUE,
     draggable: null,
     encType: null,
     form: MUST_USE_ATTRIBUTE,

src/browser/ui/dom/__tests__/DOMPropertyOperations-test.js

@@ -99,6 +99,48 @@ describe('DOMPropertyOperations', function() {
       )).toBe('');
     });
 
+    it('should create markup for booleanish properties', function() {
+      expect(DOMPropertyOperations.createMarkupForProperty(
+        'download',
+        'simple'
+      )).toBe('download="simple"');
+
+      expect(DOMPropertyOperations.createMarkupForProperty(
+        'download',
+        true
+      )).toBe('download');
+
+      expect(DOMPropertyOperations.createMarkupForProperty(
+        'download',
+        'true'
+      )).toBe('download="true"');
+
+      expect(DOMPropertyOperations.createMarkupForProperty(
+        'download',
+        false
+      )).toBe('');
+
+      expect(DOMPropertyOperations.createMarkupForProperty(
+        'download',
+        'false'
+      )).toBe('download="false"');
+
+      expect(DOMPropertyOperations.createMarkupForProperty(
+        'download',
+        undefined
+      )).toBe('');
+
+      expect(DOMPropertyOperations.createMarkupForProperty(
+        'download',
+        null
+      )).toBe('');
+
+      expect(DOMPropertyOperations.createMarkupForProperty(
+        'download',
+        0
+      )).toBe('download="0"');
+    });
+
     it('should create markup for custom attributes', function() {
       expect(DOMPropertyOperations.createMarkupForProperty(
         'aria-label',