Allow conversion of projects with unrecognized imports

src/MSBuild.Abstractions/MSBuildConversionWorkspace.cs

@@ -281,55 +281,21 @@ private ProjectStyle GetProjectStyle(IProjectRootElement projectRootElement)
                 return ProjectStyle.Custom;
             }
 
-            var cleansedImports = imports.Select(import => Path.GetFileName(import.Project));
-            var allImportsConvertibleToSdk =
-                cleansedImports.All(import =>
-                    MSBuildFacts.PropsConvertibleToSDK.Contains(import, StringComparer.OrdinalIgnoreCase) ||
-                    MSBuildFacts.TargetsConvertibleToSDK.Contains(import, StringComparer.OrdinalIgnoreCase));
-
-            if (allImportsConvertibleToSdk)
+            if (MSBuildHelpers.IsNETFrameworkMSTestProject(projectRootElement))
             {
-                if (MSBuildHelpers.IsNETFrameworkMSTestProject(projectRootElement))
-                {
-                    return ProjectStyle.MSTest;
-                }
-                else if (MSBuildHelpers.IsWPF(projectRootElement) || MSBuildHelpers.IsWinForms(projectRootElement) || MSBuildHelpers.IsDesktop(projectRootElement))
-                {
-                    return ProjectStyle.WindowsDesktop;
-                }
-                else if (MSBuildHelpers.IsWeb(projectRootElement))
-                {
-                    return ProjectStyle.Web;
-                }
-                else
-                {
-                    return ProjectStyle.Default;
-                }
+                return ProjectStyle.MSTest;
+            }
+            else if (MSBuildHelpers.IsWPF(projectRootElement) || MSBuildHelpers.IsWinForms(projectRootElement) || MSBuildHelpers.IsDesktop(projectRootElement))
+            {
+                return ProjectStyle.WindowsDesktop;
+            }
+            else if (MSBuildHelpers.IsWeb(projectRootElement))
+            {
+                return ProjectStyle.Web;
             }
             else
             {
-                Console.WriteLine("This project has custom imports that are not accepted by try-convert.");
-                Console.WriteLine("Unexpected custom imports were found:");
-
-                var customImports =
-                    cleansedImports.Where(import =>
-                        !(MSBuildFacts.PropsConvertibleToSDK.Contains(import, StringComparer.OrdinalIgnoreCase) ||
-                            MSBuildFacts.TargetsConvertibleToSDK.Contains(import, StringComparer.OrdinalIgnoreCase)));
-
-                foreach (var import in customImports)
-                {
-                    Console.WriteLine($"\t{import}");
-                }
-
-                Console.WriteLine("The following imports are considered valid for conversion:");
-
-                foreach (var import in MSBuildFacts.TargetsConvertibleToSDK.Union(MSBuildFacts.PropsConvertibleToSDK))
-                {
-                    Console.WriteLine($"\t{import}");
-                }
-
-                // It's something else, no idea what though
-                return ProjectStyle.Custom;
+                return ProjectStyle.Default;
             }
         }
 

src/MSBuild.Conversion.Facts/MSBuildFacts.cs

@@ -10,17 +10,19 @@ namespace MSBuild.Conversion.Facts
     public static class MSBuildFacts
     {
         /// <summary>
-        /// Props files which are known to be imported in standard projects created from templates that can be converted to use the SDK
+        /// Props files which are known to be imported in standard projects created from templates that can be omitted from SDK projects.
         /// </summary>
-        public static ImmutableArray<string> PropsConvertibleToSDK => ImmutableArray.Create(
+        public static ImmutableArray<string> PropsToRemove => ImmutableArray.Create(
             "Microsoft.Common.props",
-            "MSTest.TestAdapter.props"
+            "MSTest.TestAdapter.props",
+            "Microsoft.CodeDom.Providers.DotNetCompilerPlatform.props",
+            "Microsoft.Net.Compilers.props" // https://stackoverflow.com/a/60623906
         );
 
         /// <summary>
-        /// Targets files which are known to be imported in standard projects created from templates that can be converted to use the SDK.
+        /// Targets files which are known to be imported in standard projects created from templates that can be omitted from SDK projects.
         /// </summary>
-        public static ImmutableArray<string> TargetsConvertibleToSDK => ImmutableArray.Create(
+        public static ImmutableArray<string> TargetsToRemove => ImmutableArray.Create(
             "Microsoft.CSharp.targets",
             "Microsoft.VisualBasic.targets",
             "Microsoft.Portable.CSharp.targets",
@@ -31,6 +33,14 @@ public static class MSBuildFacts
             "Microsoft.WebApplication.targets"
         );
 
+        /// <summary>
+        /// Props and targets files which are recognized and can be left unchanged during conversion.
+        /// </summary>
+        public static ImmutableArray<string> ImportsToKeep => ImmutableArray.Create(
+            "Microsoft.TypeScript.Default.props",
+            "Microsoft.TypeScript.targets"
+        );
+
         /// <summary>
         /// Mapping of PCL profiles to netstandard versions.
         /// </summary>

src/MSBuild.Conversion.Project/ProjectRootElementExtensionsForConversion.cs

@@ -16,7 +16,16 @@ public static IProjectRootElement ChangeImportsAndAddSdkAttribute(this IProjectR
         {
             foreach (var import in projectRootElement.Imports)
             {
-                projectRootElement.RemoveChild(import);
+                var fileName = Path.GetFileName(import.Project);
+                if (MSBuildFacts.PropsToRemove.Contains(fileName, StringComparer.OrdinalIgnoreCase) ||
+                    MSBuildFacts.TargetsToRemove.Contains(fileName, StringComparer.OrdinalIgnoreCase))
+                {
+                    projectRootElement.RemoveChild(import);
+                }
+                else if (!MSBuildFacts.ImportsToKeep.Contains(fileName, StringComparer.OrdinalIgnoreCase))
+                {
+                    Console.WriteLine($"This project has an unrecognized custom import which may need reviewed after conversion: {fileName}");
+                }
             }
 
             if (baselineProject.ProjectStyle is ProjectStyle.WindowsDesktop && baselineProject.TargetTFM is MSBuildFacts.NetCoreApp31)