validations: treat `NaN` as a blank value

When a required number property is set to NaN, for example as a result
of coersion (`Number([1,2,3])`), the "presence" validation now correctly
reports an error.

lib/validations.js

@@ -628,6 +628,7 @@ function blank(v) {
   if (typeof v === 'undefined') return true;
   if (v instanceof Array && v.length === 0) return true;
   if (v === null) return true;
+  if (typeof v === 'number' && isNaN(v)) return true;
   if (typeof v == 'string' && v === '') return true;
   return false;
 }

test/datatype.test.js

@@ -149,6 +149,21 @@ describe('datatypes', function () {
       coerced.nested.constructor.name.should.equal('Object');
   });
 
+  it('rejects array value converted to NaN for a required property',
+  function(done) {
+    db = getSchema();
+    Model = db.define('RequiredNumber', {
+      num: { type: Number, required: true }
+    });
+    db.automigrate(function () {
+      Model.create({ num: [1,2,3] }, function(err, inst) {
+        should.exist(err);
+        err.should.have.property('name').equal('ValidationError');
+        done();
+      });
+    });
+  });
+
   describe('model option persistUndefinedAsNull', function() {
     var TestModel, isStrict;
     before(function(done) {

test/validations.test.js

@@ -279,6 +279,24 @@ describe('validations', function () {
       u.isValid().should.be.true;
     });
 
+    it('should reject NaN value as a number', function() {
+      User.validatesPresenceOf('age');
+      var u = new User();
+      u.isValid().should.be.false;
+      u.age = NaN;
+      u.isValid().should.be.false;
+      u.age = 1;
+      u.isValid().should.be.true;
+    });
+
+    it('should allow "NaN" value as a string', function() {
+      User.validatesPresenceOf('name');
+      var u = new User();
+      u.isValid().should.be.false;
+      u.name = 'NaN';
+      u.isValid().should.be.true;
+    });
+
     it('should skip validation by property (if/unless)', function () {
       User.validatesPresenceOf('domain', {unless: 'createdByScript'});