Fix issue #49 - $where operator is not evaluated last

mingo.js

@@ -1327,10 +1327,15 @@ Mingo.Query.prototype = {
 
     assert(isObject(this.__criteria), 'Criteria must be of type Object')
 
+    var whereOperator;
+
     for (var field in this.__criteria) {
       if (has(this.__criteria, field)) {
         var expr = this.__criteria[field]
-        if (inArray(['$and', '$or', '$nor', '$where'], field)) {
+        // save $where operators to be executed after other operators
+        if ('$where' === field) {
+          whereOperator = {field: field, expr: expr};
+        } else if (inArray(['$and', '$or', '$nor'], field)) {
           this._processOperator(field, field, expr)
         } else {
           // normalize expression
@@ -1342,6 +1347,11 @@ Mingo.Query.prototype = {
           }
         }
       }
+
+      if(whereOperator) {
+        this._processOperator(whereOperator.field, whereOperator.field, whereOperator.expr);
+      }
+
     }
   },
 

test/collections.js

@@ -63,3 +63,51 @@ test('Match $all with $elemMatch on nested elements', function (t) {
   var result = Mingo.find(data, criteria).count()
   t.ok(result === 1, 'can match using $all with $elemMatch on nested elements')
 })
+
+test('Evaluate $where last', function (t) {
+  t.plan(2)
+
+  var data = [
+    {
+      user: {
+        username: 'User1',
+        projects: [
+          {name: 'Project 1', rating: {complexity: 6}},
+          {name: 'Project 2', rating: {complexity: 2}}
+        ],
+        color: 'green',
+        number: 42
+      }
+    },
+    {
+      user: {
+        username: 'User2',
+        projects: [
+          {name: 'Project 1', rating: {complexity: 6}},
+          {name: 'Project 2', rating: {complexity: 8}}
+        ]
+      }
+    }
+  ]
+
+  var criteria = {
+    'user.color': {$exists: true},
+    'user.number': {$exists: true},
+    $where: 'this.user.color === "green" && this.user.number === 42'
+  }
+  // It should return one user object
+  var result = Mingo.find(data, criteria).count()
+  t.ok(result === 1, 'can safely reference properties on this using $where and $exists')
+
+  criteria = {
+    'user.color': {$exists: true},
+    'user.number': {$exists: true},
+    $and: [
+      { $where: 'this.user.color === "green"' },
+      { $where: 'this.user.number === 42' }
+    ]
+  }
+  // It should return one user object
+  var result = Mingo.find(data, criteria).count()
+  t.ok(result === 1, 'can safely reference properties on this using multiple $where operators and $exists')
+})