NH-3096 - add HQL generator for Nullable`1.GetValueOrDefault()

Author: hazzik

src/NHibernate.Test/Linq/ByMethod/GetValueOrDefaultTests.cs

@@ -0,0 +1,29 @@
+using System.Linq;
+using NUnit.Framework;
+
+namespace NHibernate.Test.Linq.ByMethod
+{
+	[TestFixture]
+	public class GetValueOrDefaultTests : LinqTestCase
+	{
+		[Test]
+		public void CoalesceInWhere()
+		{
+			var orders = db.Orders
+						   .Where(x => (x.Freight ?? 100) > 0)
+						   .ToList();
+
+			Assert.AreEqual(830, orders.Count);
+		}
+
+		[Test]
+		public void GetValueOrDefaultInWhere()
+		{
+			var orders = db.Orders
+						   .Where(x => x.Freight.GetValueOrDefault(100) > 0)
+						   .ToList();
+
+			Assert.AreEqual(830, orders.Count);
+		}
+	}
+}

src/NHibernate.Test/NHibernate.Test.csproj

@@ -502,6 +502,7 @@
     <Compile Include="Linq\ByMethod\CastTests.cs" />
     <Compile Include="Linq\ByMethod\GroupByHavingTests.cs" />
     <Compile Include="Linq\ByMethod\GroupByTests.cs" />
+    <Compile Include="Linq\ByMethod\GetValueOrDefaultTests.cs" />
     <Compile Include="Linq\CasingTest.cs" />
     <Compile Include="Linq\CharComparisonTests.cs" />
     <Compile Include="Linq\CollectionAssert.cs" />

src/NHibernate/Linq/Functions/DefaultLinqToHqlGeneratorsRegistry.cs

@@ -20,6 +20,7 @@ public DefaultLinqToHqlGeneratorsRegistry()
 			RegisterGenerator(new GenericDictionaryContainsKeyRuntimeHqlGenerator());
 			RegisterGenerator(new ToStringRuntimeMethodHqlGenerator());
 			RegisterGenerator(new LikeGenerator());
+			RegisterGenerator(new GetValueOrDefaultGenerator());
 
 			RegisterGenerator(new CompareGenerator());
 			this.Merge(new CompareGenerator());

src/NHibernate/Linq/Functions/GetValueOrDefaultGenerator.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq.Expressions;
+using System.Reflection;
+using NHibernate.Hql.Ast;
+using NHibernate.Linq.Visitors;
+using NHibernate.Util;
+
+namespace NHibernate.Linq.Functions
+{
+	internal class GetValueOrDefaultGenerator : IHqlGeneratorForMethod, IRuntimeMethodHqlGenerator
+	{
+		public bool SupportsMethod(MethodInfo method)
+		{
+			return method != null && String.Equals(method.Name, "GetValueOrDefault", StringComparison.OrdinalIgnoreCase) && method.IsMethodOf(typeof (Nullable<>));
+		}
+
+		public IHqlGeneratorForMethod GetMethodGenerator(MethodInfo method)
+		{
+			return this;
+		}
+
+		public IEnumerable<MethodInfo> SupportedMethods
+		{
+			get { throw new NotSupportedException("This is an runtime method generator"); }
+		}
+
+		public HqlTreeNode BuildHql(MethodInfo method, Expression targetObject, ReadOnlyCollection<Expression> arguments, HqlTreeBuilder treeBuilder, IHqlExpressionVisitor visitor)
+		{
+			return treeBuilder.Coalesce(visitor.Visit(targetObject).AsExpression(), visitor.Visit(arguments[0]).AsExpression());
+		}
+	}
+}

src/NHibernate/NHibernate.csproj

@@ -292,6 +292,7 @@
     <Compile Include="Linq\ExpressionTransformers\RemoveRedundantCast.cs" />
     <Compile Include="Linq\ExpressionTransformers\SimplifyCompareTransformer.cs" />
     <Compile Include="Linq\Functions\CompareGenerator.cs" />
+    <Compile Include="Linq\Functions\GetValueOrDefaultGenerator.cs" />
     <Compile Include="Linq\Functions\MathGenerator.cs" />
     <Compile Include="Linq\Functions\DictionaryGenerator.cs" />
     <Compile Include="Linq\Functions\EqualsGenerator.cs" />