Support multiple files in file-based programs

src/Cli/Microsoft.DotNet.Cli.Utils/PathUtility.cs

@@ -416,4 +416,60 @@ public static string GetDirectorySeparatorChar()
 
         return null;
     }
+
+    public static void SafeRenameDirectory(string sourceDir, string destDir)
+    {
+        if (Directory.Exists(destDir))
+        {
+            throw new IOException($"Cannot rename directory: destination '{destDir}' already exists");
+        }
+
+        // Check if destination is a subdirectory of the source
+        if (IsChildOfDirectory(sourceDir, destDir))
+        {
+            // Create a temporary location outside of the source directory
+            string tempDir = Path.Combine(
+                Path.GetDirectoryName(sourceDir) ?? Path.GetTempPath(),
+                Path.GetRandomFileName());
+
+            try
+            {
+                // First move to temp location
+                Directory.Move(sourceDir, tempDir);
+
+                // Create parent directories of destination if needed
+                EnsureDirectoryExists(Path.GetDirectoryName(destDir));
+
+                // Move from temp to final destination
+                Directory.Move(tempDir, destDir);
+            }
+            catch (Exception)
+            {
+                // Try to restore original directory if possible
+                if (Directory.Exists(tempDir) && !Directory.Exists(sourceDir))
+                {
+                    try
+                    {
+                        Directory.Move(tempDir, sourceDir);
+                    }
+                    catch
+                    {
+                        // Last resort, if we can't move back, at least don't lose the data
+                        // Leave it in the temp dir and report the location
+                        throw new IOException(
+                            $"Failed to rename directory '{sourceDir}' to '{destDir}'. " +
+                            $"Data has been moved to temporary location: {tempDir}");
+                    }
+                }
+
+                throw;
+            }
+        }
+        else
+        {
+            // For non-nested moves, we can just use Directory.Move directly
+            EnsureDirectoryExists(Path.GetDirectoryName(destDir));
+            Directory.Move(sourceDir, destDir);
+        }
+    }
 }

src/Cli/dotnet/Commands/CliCommandStrings.resx

@@ -364,12 +364,18 @@ For MSTest before 2.2.4, the timeout is used for all testcases.</value>
   <data name="CmdExpressionName" xml:space="preserve">
     <value>EXPRESSION</value>
   </data>
-  <data name="CmdFileDescription" xml:space="preserve">
-    <value>Path to the file-based program.</value>
+  <data name="FileOrDirectoryArgumentName" xml:space="preserve">
+    <value>FILE | DIRECTORY</value>
+  </data>
+  <data name="FileOrDirectoryArgumentDescription" xml:space="preserve">
+    <value>Path to the file-based program's entry point or directory of multiple entry points.</value>
   </data>
   <data name="CmdOptionForceDescription" xml:space="preserve">
     <value>Force conversion even if there are malformed directives.</value>
   </data>
+  <data name="CmdOptionSharedDirectoryNameDescription" xml:space="preserve">
+    <value>Name of the directory where non-entry-point files should be placed.</value>
+  </data>
   <data name="CmdForceRestoreOptionDescription" xml:space="preserve">
     <value>Force all dependencies to be resolved even if the last restore was successful.
 This is equivalent to deleting project.assets.json.</value>
@@ -972,9 +978,21 @@ Make the profile names distinct.</value>
   <data name="IntermediateWorkingDirOptionDescription" xml:space="preserve">
     <value>The working directory used by the command to execute.</value>
   </data>
-  <data name="InvalidFilePath" xml:space="preserve">
-    <value>The specified file must exist and have '.cs' file extension: '{0}'</value>
-    <comment>{Locked=".cs"}</comment>
+  <data name="InvalidFileOrDirectoryPath" xml:space="preserve">
+    <value>The specified path must be an existing file with '.cs' extension or an existing directory: '{0}'</value>
+    <comment>{Locked=".cs"}. {0} is file or directory path</comment>
+  </data>
+  <data name="DirectoryMustBeSpecified" xml:space="preserve">
+    <value>Since there are multiple entry points, a directory must be specified rather than a file (and all entry points will be converted together): '{0}'</value>
+    <comment>{0} is file path</comment>
+  </data>
+  <data name="NoEntryPoints" xml:space="preserve">
+    <value>Cannot convert, no entry points found: '{0}'</value>
+    <comment>{0} is directory path</comment>
+  </data>
+  <data name="SharedDirectoryNameConflicts" xml:space="preserve">
+    <value>Cannot put shared files into directory '{0}' because it conflicts with one of the entry points. Use option '--shared-directory-name' to specify a different value.</value>
+    <comment>{Locked="--shared-directory-name"}. {0} is file name without extension</comment>
   </data>
   <data name="InvalidSemVerVersionString" xml:space="preserve">
     <value>Failed to parse "{0}" as a semantic version.</value>
@@ -1492,6 +1510,14 @@ Tool '{1}' (version '{2}') was successfully installed. Entry is added to the man
   <data name="ProjectConvertAppFullName" xml:space="preserve">
     <value>Convert a file-based program to a project-based program.</value>
   </data>
+  <data name="NoTopLevelStatements" xml:space="preserve">
+    <value>The entry point of a file-based program must have top-level statements: '{0}'</value>
+    <comment>{0} is file path</comment>
+  </data>
+  <data name="EntryPointInNestedFolder" xml:space="preserve">
+    <value>Entry-point files cannot be in nested folders: '{0}'</value>
+    <comment>{0} is file path</comment>
+  </data>
   <data name="ProjectManifest" xml:space="preserve">
     <value>PROJECT_MANIFEST</value>
   </data>

src/Cli/dotnet/Commands/Project/Convert/ProjectConvertCommand.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.CommandLine;
+using System.Diagnostics;
 using Microsoft.DotNet.Cli.Commands.Run;
 using Microsoft.DotNet.Cli.Utils;
 using Microsoft.TemplateEngine.Cli.Commands;
@@ -10,48 +11,216 @@ namespace Microsoft.DotNet.Cli.Commands.Project.Convert;
 
 internal sealed class ProjectConvertCommand(ParseResult parseResult) : CommandBase(parseResult)
 {
-    private readonly string _file = parseResult.GetValue(ProjectConvertCommandParser.FileArgument) ?? string.Empty;
+    private readonly string _fileOrDirectory = parseResult.GetValue(ProjectConvertCommandParser.FileOrDirectoryArgument)!;
     private readonly string? _outputDirectory = parseResult.GetValue(SharedOptions.OutputOption)?.FullName;
     private readonly bool _force = parseResult.GetValue(ProjectConvertCommandParser.ForceOption);
+    private readonly string _sharedDirectoryName = parseResult.GetValue(ProjectConvertCommandParser.SharedDirectoryNameOption)!;
 
     public override int Execute()
     {
-        string file = Path.GetFullPath(_file);
-        if (!VirtualProjectBuildingCommand.IsValidEntryPointPath(file))
+        // Check target directory.
+        if (_outputDirectory != null && Directory.Exists(_outputDirectory))
         {
-            throw new GracefulException(CliCommandStrings.InvalidFilePath, file);
+            throw new GracefulException(CliCommandStrings.DirectoryAlreadyExists, _outputDirectory);
         }
 
-        string targetDirectory = _outputDirectory ?? Path.ChangeExtension(file, null);
-        if (Directory.Exists(targetDirectory))
+        // Check entry-point file path.
+        string fileOrDirectory = Path.GetFullPath(_fileOrDirectory);
+        bool isFile = VirtualProjectBuildingCommand.IsValidEntryPointPath(fileOrDirectory);
+        if (!isFile && !Directory.Exists(fileOrDirectory))
         {
-            throw new GracefulException(CliCommandStrings.DirectoryAlreadyExists, targetDirectory);
+            throw new GracefulException(CliCommandStrings.InvalidFileOrDirectoryPath, fileOrDirectory);
         }
 
-        // Find directives (this can fail, so do this before creating the target directory).
-        var sourceFile = VirtualProjectBuildingCommand.LoadSourceFile(file);
-        var directives = VirtualProjectBuildingCommand.FindDirectives(sourceFile, reportAllErrors: !_force, errors: null);
+        // Discover other C# files.
+        SourceFile? entryPointSourceFile = isFile ? VirtualProjectBuildingCommand.LoadSourceFile(fileOrDirectory) : null;
+        VirtualProjectBuildingCommand.DiscoverOtherFiles(
+            entryPointFile: entryPointSourceFile,
+            entryDirectory: isFile ? null : new DirectoryInfo(fileOrDirectory),
+            parseDirectivesFromOtherEntryPoints: true,
+            reportAllDirectiveErrors: !_force,
+            directiveErrors: null,
+            otherEntryPoints: out var otherEntryPoints,
+            parsedFiles: out var parsedFiles);
 
-        Directory.CreateDirectory(targetDirectory);
+        // If there are other entry points, a directory must be specified (so it's clear that we convert all the entry points, not just the specified one).
+        if (isFile && otherEntryPoints.Length != 0)
+        {
+            throw new GracefulException(CliCommandStrings.DirectoryMustBeSpecified, fileOrDirectory);
+        }
+
+        ReadOnlySpan<string> currentEntryPoint = entryPointSourceFile is { } file ? [file.Path] : [];
+        ReadOnlySpan<string> allEntryPoints = [.. currentEntryPoint, .. otherEntryPoints];
+
+        // Check there are some entry points.
+        if (allEntryPoints.Length == 0)
+        {
+            throw new GracefulException(CliCommandStrings.NoEntryPoints, fileOrDirectory);
+        }
+
+        // Discover other non-C# files and directories at the top level.
+        string sourceDirectory = isFile ? Path.GetDirectoryName(fileOrDirectory)! : fileOrDirectory;
+        string[] nonCSharpTopLevelFiles = Directory.EnumerateFiles(sourceDirectory)
+            .Where(f => !f.EndsWith(".cs", StringComparison.OrdinalIgnoreCase))
+            .ToArray();
+        string[] topLevelDirs = Directory.GetDirectories(sourceDirectory);
+
+        // We create a plan of what to do first. No changes are done here so we don't fail in an intermediate state.
+        // First we need to create Shared folder and copy all existing folders and non-entry-point or non-C# files to it.
+        // Then we convert the C# files (remove directives from them and create csproj files for the entry-point ones).
+        // That way we re-create the source directory structure inside the Shared folder and also handle a situation where user has a folder with the same name as one of the entry points
+        // (we need to move the folder first to Shared and then convert the entry point which will re-create the folder and copy the converted entry point into it).
+        var actions = new List<Action>();
 
-        var targetFile = Path.Join(targetDirectory, Path.GetFileName(file));
+        // Determine the base target directory.
+        string baseTargetDirectory;
+        if (_outputDirectory != null)
+        {
+            baseTargetDirectory = _outputDirectory;
+            actions.Add(() => Directory.CreateDirectory(baseTargetDirectory));
+        }
+        else
+        {
+            baseTargetDirectory = sourceDirectory;
+        }
+
+        string? sharedDirectory;
+        bool creatingSharedDirectory;
 
-        // If there were any directives, remove them from the file.
-        if (directives.Length != 0)
+        // If there are multiple entry points and some non-C# or non-entry-point files/dirs, we need a Shared folder.
+        Debug.Assert(parsedFiles.Count >= allEntryPoints.Length);
+        if (allEntryPoints.Length > 1 && (nonCSharpTopLevelFiles.Length > 0 || topLevelDirs.Length > 0 || parsedFiles.Count > allEntryPoints.Length))
         {
-            VirtualProjectBuildingCommand.RemoveDirectivesFromFile(directives, sourceFile.Text, targetFile);
-            File.Delete(file);
+            sharedDirectory = Path.Join(baseTargetDirectory, _sharedDirectoryName);
+            actions.Add(() => Directory.CreateDirectory(sharedDirectory));
+            creatingSharedDirectory = true;
         }
         else
         {
-            File.Move(file, targetFile);
+            // We also need to move other files to the target folder if it's specified.
+            sharedDirectory = _outputDirectory != null ? baseTargetDirectory : null;
+            creatingSharedDirectory = false;
         }
 
-        string projectFile = Path.Join(targetDirectory, Path.GetFileNameWithoutExtension(file) + ".csproj");
-        using var stream = File.Open(projectFile, FileMode.Create, FileAccess.Write);
-        using var writer = new StreamWriter(stream, Encoding.UTF8);
-        VirtualProjectBuildingCommand.WriteProjectFile(writer, directives, isVirtualProject: false);
+        // Move non-C# files and directories.
+        if (nonCSharpTopLevelFiles.Length > 0 || topLevelDirs.Length > 0)
+        {
+            if (sharedDirectory != null)
+            {
+                actions.Add(() =>
+                {
+                    foreach (var dir in topLevelDirs)
+                    {
+                        string target = GetTargetTopLevelPath(sharedDirectory, dir);
+                        PathUtility.SafeRenameDirectory(dir, target);
+                    }
+
+                    foreach (var file in nonCSharpTopLevelFiles)
+                    {
+                        string target = GetTargetTopLevelPath(sharedDirectory, file);
+                        File.Move(file, target);
+                    }
+                });
+            }
+        }
+
+        // Process C# files.
+        foreach (var parsed in parsedFiles.Values)
+        {
+            string targetDirectory;
+            bool deleteSourceFiles;
+
+            if (parsed.IsEntryPoint)
+            {
+                Debug.Assert(string.IsNullOrEmpty(Path.GetDirectoryName(Path.GetRelativePath(relativeTo: sourceDirectory, path: parsed.File.Path))),
+                    "Entry points are expected to be at the top level.");
+
+                string fileNameWithoutExtension = Path.GetFileNameWithoutExtension(parsed.File.Path);
+
+                if (creatingSharedDirectory && string.Equals(fileNameWithoutExtension, _sharedDirectoryName, StringComparison.OrdinalIgnoreCase))
+                {
+                    throw new GracefulException(CliCommandStrings.SharedDirectoryNameConflicts, _sharedDirectoryName);
+                }
+
+                // If there is a single entry point, generate the project directly in the output folder, otherwise create a subfolder.
+                if (allEntryPoints.Length > 1)
+                {
+                    targetDirectory = Path.Join(baseTargetDirectory, fileNameWithoutExtension);
+                    actions.Add(() => Directory.CreateDirectory(targetDirectory));
+                    deleteSourceFiles = true;
+                }
+                else
+                {
+                    targetDirectory = baseTargetDirectory;
+                    deleteSourceFiles = _outputDirectory != null;
+                }
+
+                // Generate a project file.
+                string projectFile = Path.Join(targetDirectory, fileNameWithoutExtension + ".csproj");
+                actions.Add(() =>
+                {
+                    using (var csprojStream = File.Open(projectFile, FileMode.Create, FileAccess.Write))
+                    using (var csprojWriter = new StreamWriter(csprojStream, Encoding.UTF8))
+                    {
+                        VirtualProjectBuildingCommand.WriteProjectFile(csprojWriter, parsed.SortedDirectives, options: new ProjectWritingOptions.Converted
+                        {
+                            SharedDirectoryName = creatingSharedDirectory ? _sharedDirectoryName : null,
+                        });
+                    }
+                });
+            }
+            else
+            {
+                // If the file is nested, we have already moved it to the shared folder, so process it in place.
+                string? relativeDirectoryPath = Path.GetDirectoryName(Path.GetRelativePath(relativeTo: sourceDirectory, path: parsed.File.Path));
+                if (!string.IsNullOrEmpty(relativeDirectoryPath))
+                {
+                    targetDirectory = Path.Join(sharedDirectory, relativeDirectoryPath);
+                    deleteSourceFiles = false;
+                }
+                else if (sharedDirectory != null)
+                {
+                    targetDirectory = sharedDirectory;
+                    deleteSourceFiles = true;
+                }
+                else
+                {
+                    Debug.Assert(_outputDirectory == null);
+                    targetDirectory = baseTargetDirectory;
+                    deleteSourceFiles = false;
+                }
+            }
+
+            // Remove directives. Write the converted file or move it if no conversion is needed.
+            string targetFilePath = GetTargetTopLevelPath(targetDirectory, parsed.File.Path);
+            actions.Add(() =>
+            {
+                if (VirtualProjectBuildingCommand.RemoveDirectivesFromFile(parsed.Directives, parsed.File.Text) is { } convertedEntryPointFileText)
+                {
+                    using var stream = File.Open(targetFilePath, FileMode.Create, FileAccess.Write);
+                    using var writer = new StreamWriter(stream, Encoding.UTF8);
+                    convertedEntryPointFileText.Write(writer);
+
+                    if (deleteSourceFiles)
+                    {
+                        File.Delete(parsed.File.Path);
+                    }
+                }
+                else if (deleteSourceFiles)
+                {
+                    File.Move(parsed.File.Path, targetFilePath);
+                }
+            });
+        }
+
+        // Execute actions.
+        actions.ForEach(static action => action());
 
         return 0;
+
+        static string GetTargetTopLevelPath(string targetDirectory, string sourceFilePath)
+        {
+            return Path.Join(targetDirectory, Path.GetFileName(sourceFilePath));
+        }
     }
 }