fixed issue with a flattening projection and still maintaining the or…

…iginal hierarchy.

source/MongoDB.Tests/IntegrationTests/Linq/MongoQueryProviderTests.cs

@@ -317,6 +317,20 @@ public void ProjectionWithConstraints()
             Assert.AreEqual(new Document("Age", new Document().Merge(Op.GreaterThan(21)).Merge(Op.LessThan(42))), queryObject.Query);
         }
 
+        [Test]
+        public void ProjectionWithLocalCreation_ChildobjectShouldNotBeNull()
+        {
+            var people = Collection.Linq()
+                .Select(p => new PersonWrapper(p, p.FirstName));
+
+            var queryObject = ((IMongoQueryable)people).GetQueryObject();
+            Assert.AreEqual(0, queryObject.Fields.Count());
+            Assert.AreEqual(0, queryObject.NumberToLimit);
+            Assert.AreEqual(0, queryObject.NumberToSkip);
+            Assert.AreEqual(0, queryObject.Query.Count);
+
+        }
+
         [Test]
         public void Regex_IsMatch()
         {

source/MongoDB/Linq/Expressions/MongoExpressionExtensions.cs

@@ -8,6 +8,14 @@ namespace MongoDB.Linq.Expressions
 {
     internal static class MongoExpressionExtensions
     {
+        public static bool HasSelectAllField(this IEnumerable<FieldDeclaration> fields)
+        {
+            if (fields == null)
+                return true;
+
+            return fields.Any(f => f.Name == "*");
+        }
+
         public static SelectExpression AddField(this SelectExpression select, FieldDeclaration field)
         {
             List<FieldDeclaration> fields = new List<FieldDeclaration>(select.Fields);

source/MongoDB/Linq/MongoQueryProvider.cs

@@ -164,9 +164,12 @@ private Expression BuildExecutionPlan(Expression expression)
 
         private ProjectionExpression Translate(Expression expression)
         {
+            var rootQueryable = new RootQueryableFinder().Find(expression);
+            var elementType = ((IQueryable)((ConstantExpression)rootQueryable).Value).ElementType;
+
             expression = PartialEvaluator.Evaluate(expression, CanBeEvaluatedLocally);
 
-            expression = new FieldBinder().Bind(expression);
+            expression = new FieldBinder().Bind(expression, elementType);
             expression = new QueryBinder(this, expression).Bind(expression);
             expression = new AggregateRewriter().Rewrite(expression);
             expression = new RedundantFieldRemover().Remove(expression);

source/MongoDB/Linq/Translators/FieldBinder.cs

@@ -17,11 +17,13 @@ internal class FieldBinder : ExpressionVisitor
 
         private Alias _alias;
         private FieldFinder _finder;
+        private Type _elementType;
 
-        public Expression Bind(Expression expression)
+        public Expression Bind(Expression expression, Type elementType)
         {
             _alias = new Alias();
             _finder = new FieldFinder();
+            _elementType = elementType;
             return Visit(expression);
         }
 
@@ -37,6 +39,14 @@ protected override Expression Visit(Expression exp)
             return base.Visit(exp);
         }
 
+        protected override Expression VisitParameter(ParameterExpression p)
+        {
+            if(p.Type == _elementType)
+                return new FieldExpression(p, _alias, "*");
+
+            return base.VisitParameter(p);
+        }
+
         private class FieldFinder : ExpressionVisitor
         {
             private Stack<string> _fieldParts;

source/MongoDB/Linq/Translators/MapReduceFinalizerFunctionBuilder.cs

@@ -57,6 +57,8 @@ protected override ReadOnlyCollection<FieldDeclaration> VisitFieldDeclarationLis
             for (int i = 0, n = fields.Count; i < n; i++)
             {
                 _currentAggregateName = fields[i].Name;
+                if (_currentAggregateName == "*")
+                    continue;
                 Visit(fields[i].Expression);
             }
 

source/MongoDB/Linq/Translators/MapReduceMapFunctionBuilder.cs

@@ -66,6 +66,8 @@ protected override ReadOnlyCollection<FieldDeclaration> VisitFieldDeclarationLis
             for (int i = 0, n = fields.Count; i < n; i++)
             {
                 _currentAggregateName = fields[i].Name;
+                if (_currentAggregateName == "*")
+                    continue;
                 Visit(fields[i].Expression);
             }
 

source/MongoDB/Linq/Translators/MapReduceReduceFunctionBuilder.cs

@@ -76,6 +76,8 @@ protected override ReadOnlyCollection<FieldDeclaration> VisitFieldDeclarationLis
             for (int i = 0, n = fields.Count; i < n; i++)
             {
                 _currentAggregateName = fields[i].Name;
+                if (_currentAggregateName == "*")
+                    continue;
                 Visit(fields[i].Expression);
             }
 

source/MongoDB/Linq/Translators/MongoQueryObjectBuilder.cs

@@ -49,7 +49,7 @@ protected override Expression VisitSelect(SelectExpression select)
                 _queryObject.ReduceFunction = new MapReduceReduceFunctionBuilder().Build(select.Fields);
                 _queryObject.FinalizerFunction = new MapReduceFinalizerFunctionBuilder().Build(select.Fields);
             }
-            else if(!_queryAttributes.IsCount)
+            else if(!_queryAttributes.IsCount && !select.Fields.HasSelectAllField())
             {
                 var fieldGatherer = new FieldGatherer();
                 foreach (var field in select.Fields)