Fixes #32028: Investigate Template Baseline tests errors

Latest `dotnet new` doesn't work with relative path for `--debug:custom-hive`... Hence make it absolute
Also switched to using `--debug:disable-sdk-templates` to avoid potential conflict between SDK and tests installed templates.

Author: DavidKarlas

src/ProjectTemplates/Shared/Project.cs

@@ -58,7 +58,7 @@ internal async Task<ProcessResult> RunDotNetNewAsync(
             // Used to set special options in MSBuild
             IDictionary<string, string> environmentVariables = null)
         {
-            var hiveArg = $"--debug:custom-hive \"{TemplatePackageInstaller.CustomHivePath}\"";
+            var hiveArg = $" --debug:disable-sdk-templates --debug:custom-hive \"{TemplatePackageInstaller.CustomHivePath}\"";
             var argString = $"new {templateName} {hiveArg}";
             environmentVariables ??= new Dictionary<string, string>();
             if (!string.IsNullOrEmpty(auth))
@@ -323,7 +323,7 @@ internal async Task<ProcessEx> RunDotNetNewRawAsync(string arguments)
                     AppContext.BaseDirectory,
                     DotNetMuxer.MuxerPathOrDefault(),
                     arguments +
-                        $" --debug:custom-hive \"{TemplatePackageInstaller.CustomHivePath}\"" +
+                        $" --debug:disable-sdk-templates --debug:custom-hive \"{TemplatePackageInstaller.CustomHivePath}\"" +
                         $" -o {TemplateOutputDir}");
                 await result.Exited;
                 return result;

src/ProjectTemplates/Shared/TemplatePackageInstaller.cs

@@ -43,11 +43,11 @@ internal static class TemplatePackageInstaller
             "Microsoft.AspNetCore.Blazor.Templates",
         };
 
-        public static string CustomHivePath { get; } = (string.IsNullOrEmpty(Environment.GetEnvironmentVariable("helix")))
+        public static string CustomHivePath { get; } = Path.GetFullPath((string.IsNullOrEmpty(Environment.GetEnvironmentVariable("helix")))
                      ? typeof(TemplatePackageInstaller)
                          .Assembly.GetCustomAttributes<AssemblyMetadataAttribute>()
                          .Single(s => s.Key == "CustomTemplateHivePath").Value
-                     : Path.Combine("Hives", ".templateEngine");
+                     : Path.Combine("Hives", ".templateEngine"));
 
         public static async Task EnsureTemplatingEngineInitializedAsync(ITestOutputHelper output)
         {
@@ -78,7 +78,9 @@ public static async Task<ProcessEx> RunDotNetNew(ITestOutputHelper output, strin
                 output,
                 AppContext.BaseDirectory,
                 DotNetMuxer.MuxerPathOrDefault(),
-                $"new {arguments} --debug:custom-hive \"{CustomHivePath}\"");
+                //--debug:disable-sdk-templates means, don't include C:\Program Files\dotnet\templates, aka. what comes with SDK, so we don't need to uninstall
+                //--debug:custom-hive means, don't install templates on CI/developer machine, instead create new temporary instance
+                $"new {arguments} --debug:disable-sdk-templates --debug:custom-hive \"{CustomHivePath}\"");
 
             await proc.Exited;
 
@@ -105,23 +107,12 @@ private static async Task InstallTemplatePackages(ITestOutputHelper output)
 
             Assert.Equal(4, builtPackages.Length);
 
-            /*
-             * The templates are indexed by path, for example:
-              &USERPROFILE%\.templateengine\dotnetcli\v5.0.100-alpha1-013788\packages\nunit3.dotnetnew.template.1.6.1.nupkg
-                Templates:
-                    NUnit 3 Test Project (nunit) C#
-                    NUnit 3 Test Item (nunit-test) C#
-                    NUnit 3 Test Project (nunit) F#
-                    NUnit 3 Test Item (nunit-test) F#
-                    NUnit 3 Test Project (nunit) VB
-                    NUnit 3 Test Item (nunit-test) VB
-                Uninstall Command:
-                    dotnet new -u &USERPROFILE%\.templateengine\dotnetcli\v5.0.100-alpha1-013788\packages\nunit3.dotnetnew.template.1.6.1.nupkg
-
-             * We don't want to construct this path so we'll rely on dotnet new --uninstall --help to construct the uninstall command.
-             */
-            // Workaround for https://github.com/dotnet/sdk/issues/16906
-            // await UninstallExistingTemplatesAsync(output);
+            await VerifyCannotFindTemplateAsync(output, "web");
+            await VerifyCannotFindTemplateAsync(output, "webapp");
+            await VerifyCannotFindTemplateAsync(output, "mvc");
+            await VerifyCannotFindTemplateAsync(output, "react");
+            await VerifyCannotFindTemplateAsync(output, "reactredux");
+            await VerifyCannotFindTemplateAsync(output, "angular");
 
             foreach (var packagePath in builtPackages)
             {
@@ -135,35 +126,6 @@ NUnit 3 Test Item (nunit-test) VB
             await VerifyCanFindTemplate(output, "react");
         }
 
-        private static async Task UninstallExistingTemplatesAsync(ITestOutputHelper output)
-        {
-            var proc = await RunDotNetNew(output, "--uninstall --help");
-            var lines = proc.Output.Split(Environment.NewLine);
-
-            // Remove any previous or prebundled version of the template packages
-            foreach (var packageName in _templatePackages)
-            {
-                // Depending on the ordering, there may be multiple matches:
-                // Microsoft.DotNet.Web.Spa.ProjectTemplates.3.0.3.0.0-preview7.*.nupkg
-                // Microsoft.DotNet.Web.Spa.ProjectTemplates.3.0.0-preview7.*.nupkg
-                // Error on the side of caution and uninstall all of them
-                foreach (var command in lines.Where(l => l.Contains("dotnet new") && l.Contains(packageName, StringComparison.OrdinalIgnoreCase)))
-                {
-                    var uninstallCommand = command.TrimStart();
-                    Debug.Assert(uninstallCommand.StartsWith("dotnet new", StringComparison.Ordinal));
-                    uninstallCommand = uninstallCommand.Substring("dotnet new".Length);
-                    await RunDotNetNew(output, uninstallCommand);
-                }
-            }
-
-            await VerifyCannotFindTemplateAsync(output, "web");
-            await VerifyCannotFindTemplateAsync(output, "webapp");
-            await VerifyCannotFindTemplateAsync(output, "mvc");
-            await VerifyCannotFindTemplateAsync(output, "react");
-            await VerifyCannotFindTemplateAsync(output, "reactredux");
-            await VerifyCannotFindTemplateAsync(output, "angular");
-        }
-
         private static async Task VerifyCanFindTemplate(ITestOutputHelper output, string templateName)
         {
             var proc = await RunDotNetNew(output, $"");