[xbuild] Exists should be false for empty values

BXC17802 - xbuild evaluates Exist wrongly when the item group does not exist

2 files changed, 33 insertions, 0 deletions

diff --git a/mcs/class/Microsoft.Build.Engine/Microsoft.Build.BuildEngine/ConditionFunctionExpression.cs b/mcs/class/Microsoft.Build.Engine/Microsoft.Build.BuildEngine/ConditionFunctionExpression.cs
index 7140e50566d..308211b16fb 100644
--- a/mcs/class/Microsoft.Build.Engine/Microsoft.Build.BuildEngine/ConditionFunctionExpression.cs
+++ b/mcs/class/Microsoft.Build.Engine/Microsoft.Build.BuildEngine/ConditionFunctionExpression.cs
@@ -103,6 +103,9 @@ namespace Microsoft.Build.BuildEngine {
 		// FIXME imported projects
 		static bool Exists (string file, Project context)
 		{
+			if (string.IsNullOrEmpty (file))
+				return false;
+
 			string directory  = null;
 			
 			if (context.FullFileName != String.Empty)
diff --git a/mcs/class/Microsoft.Build.Engine/Test/Microsoft.Build.BuildEngine/BuildChooseTest.cs b/mcs/class/Microsoft.Build.Engine/Test/Microsoft.Build.BuildEngine/BuildChooseTest.cs
index 01b2ab3b0d1..3da4b97cbc6 100644
--- a/mcs/class/Microsoft.Build.Engine/Test/Microsoft.Build.BuildEngine/BuildChooseTest.cs
+++ b/mcs/class/Microsoft.Build.Engine/Test/Microsoft.Build.BuildEngine/BuildChooseTest.cs
@@ -400,5 +400,35 @@ namespace MonoTests.Microsoft.Build.BuildEngine {
 			
 			Assert.AreEqual ("no", project.GetEvaluatedProperty ("Exists"), "A1");
 		}
+
+		[Test]
+		public void EmptyExistsCondition()
+		{
+			string documentString = @"
+				<Project xmlns='http://schemas.microsoft.com/developer/msbuild/2003'>
+					<Choose>
+						<When Condition=""Exists('$(UndefinedProperty)')"">
+							<PropertyGroup>
+								<Exists>yes</Exists>
+							</PropertyGroup>
+						</When>
+						<Otherwise>
+							<PropertyGroup>
+								<Exists>no</Exists>
+							</PropertyGroup>
+						</Otherwise>
+					</Choose>
+				</Project>
+			";
+
+			Engine engine = new Engine (Consts.BinPath);
+			Project project = engine.CreateNewProject ();
+			//assign a real filename to be used as base path for the Exists
+			project.FullFileName = typeof (BuildChooseTest).Assembly.Location;
+
+			project.LoadXml (documentString);
+
+			Assert.AreEqual ("no", project.GetEvaluatedProperty ("Exists"), "A1");
+		}
 	}
 }