Add exclusion for PublishDir in DefaultItemExcludes

Co-authored-by: baronfel <[email protected]>

Author: Copilot

src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.DefaultItems.targets

@@ -51,6 +51,12 @@ Copyright (c) .NET Foundation. All rights reserved.
     <DefaultExcludesInProjectFolder>$(DefaultExcludesInProjectFolder);$(DefaultItemExcludesInProjectFolder);**/.*/**</DefaultExcludesInProjectFolder>
   </PropertyGroup>
 
+  <!-- Exclude PublishDir to prevent published artifacts from being included in subsequent builds/publishes.
+       This is especially important for file-based apps where PublishDir is set to ./artifacts/<appname> next to the app file. -->
+  <PropertyGroup Condition="'$(PublishDir)' != ''">
+    <DefaultItemExcludes>$(DefaultItemExcludes);$(PublishDir)/**</DefaultItemExcludes>
+  </PropertyGroup>
+
   <!-- Set the default versions of the NETStandard.Library or Microsoft.NETCore.App packages to reference.
        The implicit package references themselves are defined in Microsoft.NET.Sdk.props, so that they can be overridden
        in the project file. -->

test/Microsoft.NET.Build.Tests/GivenThereAreDefaultItems.cs

@@ -854,6 +854,35 @@ public void It_does_not_include_Windows_App_SDK_items_if_Windows_App_SDK_is_abse
                 .BeEmpty();
         }
 
+        [Fact]
+        public void It_excludes_items_in_publish_directory()
+        {
+            Action<GetValuesCommand> setup = getValuesCommand =>
+            {
+                // Create a PublishDir with a JSON file (simulating a previous publish)
+                string publishDir = Path.Combine(getValuesCommand.ProjectRootPath, "artifacts", "TestLibrary");
+                WriteFile(Path.Combine(publishDir, "appsettings.json"),
+                    "{ \"Setting\": \"Value\" }");
+
+                WriteFile(Path.Combine(getValuesCommand.ProjectRootPath, "Code", "Class1.cs"),
+                    "public class Class1 {}");
+            };
+
+            Action<XDocument> projectChanges = project =>
+            {
+                var ns = project.Root.Name.Namespace;
+
+                var propertyGroup = new XElement(ns + "PropertyGroup");
+                project.Root.Add(propertyGroup);
+                propertyGroup.Add(new XElement(ns + "PublishDir", "artifacts\\TestLibrary\\"));
+            };
+
+            var noneItems = GivenThatWeWantToBuildALibrary.GetValuesFromTestLibrary(Log, _testAssetsManager, "None", setup, projectChanges: projectChanges);
+
+            // The appsettings.json file in the PublishDir should not be included in None items
+            noneItems.Should().NotContain(item => item.Contains("appsettings.json"));
+        }
+
         void RemoveGeneratedCompileItems(List<string> compileItems)
         {
             //  Remove auto-generated compile items.