Error in InitCommand when solution and project file are in the same directory

src/Aspire.Cli/Commands/InitCommand.cs

@@ -175,6 +175,26 @@ private async Task<int> InitializeExistingSolutionAsync(InitContext initContext,
     {
         var solutionFile = initContext.SelectedSolutionFile!;
 
+        // Verify that the solution directory does not contain project files.
+        // If the solution and a project file are in the same directory, the AppHost
+        // and ServiceDefaults directories would be created inside that project which
+        // is not supported.
+        var solutionDirectory = solutionFile.Directory!;
+        var projectFilesInSolutionDir = solutionDirectory.EnumerateFiles("*.*proj")
+            .Where(f => DotNetAppHostProject.s_projectExtensions.Contains(f.Extension, StringComparer.OrdinalIgnoreCase))
+            .ToList();
+
+        if (projectFilesInSolutionDir.Count > 0)
+        {
+            InteractionService.DisplayError(
+                string.Format(
+                    CultureInfo.CurrentCulture,
+                    InitCommandStrings.SolutionAndProjectInSameDirectory,
+                    solutionFile.Name,
+                    projectFilesInSolutionDir[0].Name));
+            return ExitCodeConstants.FailedToCreateNewProject;
+        }
+
         initContext.GetSolutionProjectsOutputCollector = new OutputCollector();
         var (getSolutionExitCode, solutionProjects) = await InteractionService.ShowStatusAsync("Reading solution...", async () =>
         {

src/Aspire.Cli/Projects/DotNetAppHostProject.cs

@@ -34,7 +34,7 @@ internal sealed class DotNetAppHostProject : IAppHostProject
     private readonly Diagnostics.FileLoggerProvider _fileLoggerProvider;
 
     private static readonly string[] s_detectionPatterns = ["*.csproj", "*.fsproj", "*.vbproj", "apphost.cs"];
-    private static readonly string[] s_projectExtensions = [".csproj", ".fsproj", ".vbproj"];
+    internal static readonly string[] s_projectExtensions = [".csproj", ".fsproj", ".vbproj"];
 
     public DotNetAppHostProject(
         IDotNetCliRunner runner,

src/Aspire.Cli/Resources/InitCommandStrings.resx

@@ -96,4 +96,7 @@
   <data name="ResolvingTemplateVersion" xml:space="preserve">
     <value>Resolving template version...</value>
   </data>
+  <data name="SolutionAndProjectInSameDirectory" xml:space="preserve">
+    <value>The solution file '{0}' and project file '{1}' are in the same directory. The AppHost and ServiceDefaults projects cannot be created inside an existing project directory. Move the solution file to a parent directory or the project file to a subdirectory.</value>
+  </data>
 </root>

tests/Aspire.Cli.Tests/Commands/InitCommandTests.cs

@@ -14,6 +14,103 @@ namespace Aspire.Cli.Tests.Commands;
 
 public class InitCommandTests(ITestOutputHelper outputHelper)
 {
+    [Theory]
+    [InlineData("Test.csproj")]
+    [InlineData("Test.fsproj")]
+    [InlineData("Test.vbproj")]
+    public async Task InitCommand_WhenSolutionAndProjectInSameDirectory_ReturnsError(string projectFileName)
+    {
+        // Arrange
+        using var workspace = TemporaryWorkspace.Create(outputHelper);
+
+        // Create a solution file and a project file in the same directory
+        var solutionFile = new FileInfo(Path.Combine(workspace.WorkspaceRoot.FullName, "Test.sln"));
+        File.WriteAllText(solutionFile.FullName, "Fake solution file");
+
+        var projectFile = new FileInfo(Path.Combine(workspace.WorkspaceRoot.FullName, projectFileName));
+        File.WriteAllText(projectFile.FullName, "<Project />");
+
+        var services = CliTestHelper.CreateServiceCollection(workspace, outputHelper, options =>
+        {
+            options.DotNetCliRunnerFactory = (sp) =>
+            {
+                var runner = new TestDotNetCliRunner();
+                // GetSolutionProjectsAsync should not be called because the check
+                // happens before reading solution projects
+                runner.GetSolutionProjectsAsyncCallback = (_, _, _) =>
+                {
+                    throw new InvalidOperationException("GetSolutionProjectsAsync should not be called when solution and project are in the same directory.");
+                };
+                return runner;
+            };
+        });
+
+        var serviceProvider = services.BuildServiceProvider();
+        var initCommand = serviceProvider.GetRequiredService<InitCommand>();
+
+        // Act
+        var parseResult = initCommand.Parse("init");
+        var exitCode = await parseResult.InvokeAsync().DefaultTimeout();
+
+        // Assert
+        Assert.Equal(ExitCodeConstants.FailedToCreateNewProject, exitCode);
+    }
+
+    [Fact]
+    public async Task InitCommand_WhenSolutionDirectoryHasNoProjectFiles_Proceeds()
+    {
+        // Arrange
+        using var workspace = TemporaryWorkspace.Create(outputHelper);
+
+        // Create a solution file only (no project files in the same directory)
+        var solutionFile = new FileInfo(Path.Combine(workspace.WorkspaceRoot.FullName, "Test.sln"));
+        File.WriteAllText(solutionFile.FullName, "Fake solution file");
+
+        var getSolutionProjectsCalled = false;
+        var services = CliTestHelper.CreateServiceCollection(workspace, outputHelper, options =>
+        {
+            options.DotNetCliRunnerFactory = (sp) =>
+            {
+                var runner = new TestDotNetCliRunner();
+                runner.GetSolutionProjectsAsyncCallback = (_, _, _) =>
+                {
+                    getSolutionProjectsCalled = true;
+                    // Return success with no projects - the test verifies the check passed
+                    return (0, Array.Empty<FileInfo>());
+                };
+                runner.NewProjectAsyncCallback = (_, _, outputPath, _, _) =>
+                {
+                    // Create the expected directories so the code can find them
+                    var appHostDir = Path.Combine(outputPath, "Test.AppHost");
+                    var serviceDefaultsDir = Path.Combine(outputPath, "Test.ServiceDefaults");
+                    Directory.CreateDirectory(appHostDir);
+                    Directory.CreateDirectory(serviceDefaultsDir);
+                    File.WriteAllText(Path.Combine(appHostDir, "Test.AppHost.csproj"), "<Project />");
+                    File.WriteAllText(Path.Combine(serviceDefaultsDir, "Test.ServiceDefaults.csproj"), "<Project />");
+                    return 0;
+                };
+                return runner;
+            };
+            options.PackagingServiceFactory = (sp) =>
+            {
+                return new TestPackagingService();
+            };
+        });
+
+        var serviceProvider = services.BuildServiceProvider();
+        var initCommand = serviceProvider.GetRequiredService<InitCommand>();
+
+        // Act
+        var parseResult = initCommand.Parse("init");
+        var exitCode = await parseResult.InvokeAsync().DefaultTimeout();
+
+        // Assert - the command should have proceeded past the directory check and created projects
+        Assert.True(getSolutionProjectsCalled, "GetSolutionProjectsAsync should have been called when no project files are in the solution directory.");
+        Assert.Equal(ExitCodeConstants.Success, exitCode);
+        Assert.True(File.Exists(Path.Combine(workspace.WorkspaceRoot.FullName, "Test.AppHost", "Test.AppHost.csproj")));
+        Assert.True(File.Exists(Path.Combine(workspace.WorkspaceRoot.FullName, "Test.ServiceDefaults", "Test.ServiceDefaults.csproj")));
+    }
+
     [Fact]
     public void InitContext_RequiredAppHostFramework_ReturnsHighestTfm()
     {