Fix files kept in use in XslTransformation (#6946)

Author: lanfeust69

src/Tasks.UnitTests/XslTransformation_Tests.cs

@@ -13,6 +13,7 @@
 using System.Text.RegularExpressions;
 using System.Xml.Xsl;
 using System.Xml;
+using Shouldly;
 using Xunit;
 
 namespace Microsoft.Build.UnitTests
@@ -386,7 +387,7 @@ public void OutputTest()
         /// Setting correct "Parameter" parameters for Xsl.
         /// </summary>
         [Fact]
-        public void XsltParamatersCorrect()
+        public void XsltParametersCorrect()
         {
             string dir;
             TaskItem[] xmlPaths;
@@ -780,6 +781,39 @@ public void OutputFileCannotBeWritten()
             CleanUp(dir);
         }
 
+        /// <summary>
+        /// The files are not kept locked by the task
+        /// </summary>
+        [Fact]
+        public void InputFilesDontLock()
+        {
+            string dir;
+            TaskItem[] xmlPaths;
+            TaskItem xslPath;
+            TaskItem[] outputPaths;
+            MockEngine engine;
+            Prepare(out dir, out xmlPaths, out xslPath, out _, out outputPaths, out _, out _, out engine);
+
+            // Test with files
+            {
+                XslTransformation t = new XslTransformation();
+                t.BuildEngine = engine;
+                t.XmlInputPaths = xmlPaths;
+                t.XslInputPath = xslPath;
+                t.OutputPaths = outputPaths;
+
+                t.Execute().ShouldBeTrue();
+                string xmlInputPath = xmlPaths[0].ItemSpec;
+                File.Delete(xmlInputPath); // this should succeed (file not locked by task)
+                File.Exists(xmlInputPath).ShouldBeFalse();
+                string xslInputPath = xslPath.ItemSpec;
+                File.Delete(xslInputPath); // this should succeed (file not locked by task)
+                File.Exists(xslInputPath).ShouldBeFalse();
+            }
+
+            CleanUp(dir);
+        }
+
         /// <summary>
         /// XslDocument that throws runtime exception.
         /// </summary>

src/Tasks/XslTransformation.cs

@@ -334,9 +334,9 @@ public XmlReader CreateReader(int itemPos)
             {
                 if (XmlMode == XmlModes.XmlFile)
                 {
-                    return XmlReader.Create(new StreamReader(_data[itemPos]), null, _data[itemPos]);
+                    return XmlReader.Create(new StreamReader(_data[itemPos]), new XmlReaderSettings { CloseInput = true }, _data[itemPos]);
                 }
-                else // xmlModes.Xml 
+                else // xmlModes.Xml
                 {
                     return XmlReader.Create(new StringReader(_data[itemPos]));
                 }
@@ -459,7 +459,10 @@ public XslCompiledTransform LoadXslt(bool useTrustedSettings)
                             _log.LogMessageFromResources(MessageImportance.Low, "XslTransform.UseTrustedSettings", _data);
                         }
 
-                        xslct.Load(new XPathDocument(XmlReader.Create(new StreamReader(_data), null, _data)), settings, new XmlUrlResolver());
+                        using (XmlReader reader = XmlReader.Create(new StreamReader(_data), new XmlReaderSettings { CloseInput = true }, _data))
+                        {
+                            xslct.Load(new XPathDocument(reader), settings, new XmlUrlResolver());
+                        }
                         break;
                     case XslModes.XsltCompiledDll:
 #if FEATURE_COMPILED_XSL