FieldStyler#isApplied added

Field stylers now determine whether they've been applied to the target field
on their own, which solves the problem of the system getting out of sync.

* src/ui/styler/ErrorFieldStyler.js (isApplied): Added
* src/ui/styler/FieldStyler.js (isApplied): Added
* src/ui/styler/NaFieldStyler.js (isApplied): Added
* test/ui/styler/NaFieldStylerTest.js: Test for #isApplied

src/ui/styler/ErrorFieldStyler.js

@@ -35,6 +35,24 @@ module.exports = Class( 'ErrorFieldStyler' )
     },
 
 
+    /**
+     * Determines whether the field has been styled
+     *
+     * Having this predicate on the styler rather than the field ensures
+     * that, even if the two somehow get out of sync (or styles are applied
+     * elsewhere), application/revocation will function sanely.
+     *
+     * @param {DomField}            field   field to style
+     * @param {HTMLElement}         element DOM element to style
+     *
+     * @return {boolean} whether FIELD has been styled by this styler
+     */
+    'public isApplied': function( field, element )
+    {
+        return /\binvalid_field\b/.test( element.className );
+    },
+
+
     'public applyStyle': function( field, element, row, msg )
     {
         var _self = this;

src/ui/styler/FieldStyler.js

@@ -36,6 +36,20 @@ module.exports = AbstractClass( 'FieldStyler',
      */
     'abstract public getId': [],
 
+    /**
+     * Determines whether the field has been styled
+     *
+     * Having this predicate on the styler rather than the field ensures
+     * that, even if the two somehow get out of sync (or styles are applied
+     * elsewhere), application/revocation will function sanely.
+     *
+     * @param {DomField}            field   field to style
+     * @param {HTMLElement}         element DOM element to style
+     *
+     * @return {boolean} whether FIELD has been styled by this styler
+     */
+    'abstract public isApplied': [ 'field', 'element' ],
+
     /**
      * Apply style to field
      *

src/ui/styler/NaFieldStyler.js

@@ -43,6 +43,24 @@ module.exports = Class( 'NaFieldStyler' )
     },
 
 
+    /**
+     * Determines whether the field has been styled
+     *
+     * Having this predicate on the styler rather than the field ensures
+     * that, even if the two somehow get out of sync (or styles are applied
+     * elsewhere), application/revocation will function sanely.
+     *
+     * @param {DomField}            field   field to style
+     * @param {HTMLElement}         element DOM element to style
+     *
+     * @return {boolean} whether FIELD has been styled by this styler
+     */
+    'public isApplied': function( field, element )
+    {
+        return /\bhidden\b/.test( element.className );
+    },
+
+
     /**
      * Apply style to field
      *

test/ui/styler/NaFieldStylerTest.js

@@ -221,6 +221,30 @@ describe( 'ui.styler.NaFieldStyler', function()
     } );
 
 
+    describe( '#isApplied', function()
+    {
+        it( 'recognizes when applied', function()
+        {
+            var element = {
+                className: '',
+            };
+
+            var sut   = Sut(),
+                field = getStubField( element );
+
+            sut.applyStyle( field, element, [] );
+
+            expect( sut.isApplied( field, element ) )
+                .to.be.true;
+
+            sut.revokeStyle( field, element, [] );
+
+            expect( sut.isApplied( field, element ) )
+                .to.be.false;
+        } );
+    } );
+
+
     describe( 'protected API', function()
     {
         describe( '#isSubField', function()