Support loading parameters from properties for Type=Class.

Samples/Directory.Build.targets

@@ -64,6 +64,31 @@
     </Task>
   </UsingTask>
 
+  <!-- A simple in-line class task which inherits parameters from its base class -->
+  <UsingTask TaskName="InterceptingCopy"
+             TaskFactory="CodeTaskFactory"
+             AssemblyFile="$(RoslynCodeTaskFactory)"
+             Condition=" '$(RoslynCodeTaskFactory)' != '' ">
+    <Task>
+      <Reference Include="Microsoft.Build.Tasks.Core"/>
+      <Code Type="Class" Language="cs">
+        <![CDATA[
+          using Microsoft.Build.Framework;
+          using System;
+
+          public class InterceptingCopy : Microsoft.Build.Tasks.Copy
+          {
+            public override bool Execute()
+            {
+              Log.LogMessage(MessageImportance.High, "Copying '{0}' to '{1}'", String.Join(", ", (object[])SourceFiles), String.Join(", ", (object[])DestinationFiles));
+              return base.Execute();
+            }
+          }
+        ]]>
+      </Code>
+    </Task>
+  </UsingTask>
+
   <Target Name="RunSampleTask" AfterTargets="Build">
     <!-- Call the compiled task -->
     <MySample Parameter1="A value for parameter 1" Parameter2="A value for parameter 2">
@@ -84,6 +109,8 @@
     </PathGetFileName>
 
     <Message Text="File name: '$(MyFileName)'" Importance="High" />
+
+    <InterceptingCopy SourceFiles="Class1.cs" DestinationFiles="$(OutputPath)CopyOfClass1.cs" />
   </Target>
 
 </Project>

src/RoslynCodeTaskFactory.UnitTests/CodeTaskFactoryTests.cs

@@ -152,6 +152,21 @@ public void CodeLanguageFromTaskBody()
             TryLoadTaskBodyAndExpectSuccess("<Code Language=\"ViSuAl BaSic\">code</Code>", expectedCodeLanguage: "VB");
         }
 
+        [Test]
+        public void CodeTypeClassIgnoresParameterGroupWarning()
+        {
+            TryLoadTaskBodyAndExpectSuccess(
+                taskBody: "<Code Type=\"Class\">code</Code>",
+                parameters: new[]
+                {
+                    new TaskPropertyInfo("P", typeof(string), false, false),
+                },
+                expectedWarningMessages: new[]
+                {
+                    "Parameters are discovered through reflection for Type=\"Class\". Values specified in <ParameterGroup/> will be ignored.",
+                });
+        }
+
         [Test]
         public void CodeTypeFromTaskBody()
         {
@@ -466,7 +481,8 @@ private void TryLoadTaskBodyAndExpectSuccess(
             ISet<string> expectedNamespaces = null,
             string expectedCodeLanguage = null,
             CodeTaskFactoryCodeType? expectedCodeType = null,
-            string expectedSourceCode = null)
+            string expectedSourceCode = null,
+            IReadOnlyList<string> expectedWarningMessages = null)
         {
             MockBuildEngine buildEngine = new MockBuildEngine();
 
@@ -478,6 +494,7 @@ private void TryLoadTaskBodyAndExpectSuccess(
             bool success = CodeTaskFactory.TryLoadTaskBody(log, TaskName, taskBody, parameters ?? new List<TaskPropertyInfo>(), out TaskInfo taskInfo);
 
             buildEngine.Errors.ShouldBe(new string[0]);
+            buildEngine.Warnings.ShouldBe(expectedWarningMessages ?? new string[0]);
 
             Assert.True(success);
 
@@ -523,6 +540,8 @@ private sealed class MockBuildEngine : IBuildEngine
 
             public string ProjectFileOfTaskNode { get; } = String.Empty;
 
+            public IEnumerable<string> Warnings => Events.OfType<BuildWarningEventArgs>().Select(i => i.Message);
+
             public bool BuildProjectFile(string projectFileName, string[] targetNames, IDictionary globalProperties, IDictionary targetOutputs)
             {
                 throw new NotSupportedException();

src/RoslynCodeTaskFactory/CodeTaskFactory.cs

@@ -187,6 +187,28 @@ public bool Initialize(string taskName, IDictionary<string, TaskPropertyInfo> pa
                 TaskType = assembly.GetExportedTypes().FirstOrDefault(type => type.Name.Equals(taskName));
             }
 
+            if (TaskType != null)
+            {
+                // Perform automatic parameter detection if the user supplied a class.
+                // This reduces the burden of the developer by not requiring them to
+                // manually specify <ParameterGroup/>.
+                //
+                if (taskInfo.CodeType == CodeTaskFactoryCodeType.Class)
+                {
+                    PropertyInfo[] properties = TaskType.GetProperties(BindingFlags.Instance | BindingFlags.Public);
+                    _parameters = new TaskPropertyInfo[properties.Length];
+                    for (int i = 0; i < properties.Length; i++)
+                    {
+                        PropertyInfo property = properties[i];
+                        _parameters[i] = new TaskPropertyInfo(
+                            property.Name,
+                            property.PropertyType,
+                            property.GetCustomAttribute<OutputAttribute>() != null,
+                            property.GetCustomAttribute<RequiredAttribute>() != null);
+                    }
+                }
+            }
+
             AppDomain.CurrentDomain.AssemblyResolve += AppDomain_AssemblyResolve;
 
             // Initialization succeeded if we found a type matching the task name from the compiled assembly
@@ -395,6 +417,13 @@ internal static bool TryLoadTaskBody(TaskLoggingHelper log, string taskName, str
                 taskInfo.CodeType = codeType;
             }
 
+            // Warn that <ParameterGroup/> is ignored if any parameters are supplied when Type="Class".
+            //
+            if (taskInfo.CodeType == CodeTaskFactoryCodeType.Class && parameters.Any())
+            {
+                log.LogWarningWithCodeFromResources("CodeTaskFactory_ParameterGroupIgnoredForCodeTypeClass");
+            }
+
             if (languageAttribute != null)
             {
                 if (String.IsNullOrWhiteSpace(languageAttribute.Value))

src/RoslynCodeTaskFactory/Properties/Strings.resx

@@ -159,6 +159,9 @@
     <value>MSB3428: You must specify source code within the Code element or a path to a file containing source code.</value>
     <comment>{StrBegin="MSB3428: "}</comment>
   </data>
+  <data name="CodeTaskFactory_ParameterGroupIgnoredForCodeTypeClass" xml:space="preserve">
+    <value>Parameters are discovered through reflection for Type="Class". Values specified in &lt;ParameterGroup/&gt; will be ignored.</value>
+  </data>
   <data name="CodeTaskFactory_WaitingForDebugger" xml:space="preserve">
     <value>Waiting for debugger to attach ({0} PID {1}).  Press enter to continue...</value>
   </data>