Add basic support for 'dotnet run file.cs'

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

@@ -41,13 +41,7 @@ public static string MSBuildVersion
         // True if, given current state of the class, MSBuild would be executed in its own process.
         public bool ExecuteMSBuildOutOfProc => _forwardingApp != null;
 
-        private readonly Dictionary<string, string> _msbuildRequiredEnvironmentVariables =
-            new()
-            {
-                { "MSBuildExtensionsPath", MSBuildExtensionsPathTestHook ?? AppContext.BaseDirectory },
-                { "MSBuildSDKsPath", GetMSBuildSDKsPath() },
-                { "DOTNET_HOST_PATH", GetDotnetPath() },
-            };
+        private readonly Dictionary<string, string> _msbuildRequiredEnvironmentVariables = GetMSBuildRequiredEnvironmentVariables();
 
         private readonly List<string> _msbuildRequiredParameters =
             [ "-maxcpucount", "-verbosity:m" ];
@@ -205,6 +199,16 @@ private static string GetDotnetPath()
             return new Muxer().MuxerPath;
         }
 
+        internal static Dictionary<string, string> GetMSBuildRequiredEnvironmentVariables()
+        {
+            return new()
+            {
+                { "MSBuildExtensionsPath", MSBuildExtensionsPathTestHook ?? AppContext.BaseDirectory },
+                { "MSBuildSDKsPath", GetMSBuildSDKsPath() },
+                { "DOTNET_HOST_PATH", GetDotnetPath() },
+            };
+        }
+
         private static bool IsRestoreSources(string arg)
         {
             return arg.StartsWith("/p:RestoreSources=", StringComparison.OrdinalIgnoreCase) ||

src/Cli/dotnet/commands/VirtualProjectBuildingCommand.cs

@@ -0,0 +1,193 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#nullable enable
+
+using System.Xml;
+using Microsoft.Build.Construction;
+using Microsoft.Build.Definition;
+using Microsoft.Build.Evaluation;
+using Microsoft.Build.Execution;
+using Microsoft.Build.Framework;
+using Microsoft.Build.Logging;
+using Microsoft.DotNet.Cli.Utils;
+
+namespace Microsoft.DotNet.Tools;
+
+/// <summary>
+/// Used to build a virtual project file in memory to support <c>dotnet run file.cs</c>.
+/// </summary>
+internal sealed class VirtualProjectBuildingCommand
+{
+    public Dictionary<string, string> GlobalProperties { get; } = new(StringComparer.OrdinalIgnoreCase);
+    public required string EntryPointFileFullPath { get; init; }
+
+    public int Execute(string[] binaryLoggerArgs, LoggerVerbosity verbosity)
+    {
+        var binaryLogger = GetBinaryLogger(binaryLoggerArgs);
+        var consoleLogger = new ConsoleLogger(verbosity);
+        Dictionary<string, string?> savedEnvironmentVariables = new();
+        try
+        {
+            // Set environment variables.
+            foreach (var (key, value) in MSBuildForwardingAppWithoutLogging.GetMSBuildRequiredEnvironmentVariables())
+            {
+                savedEnvironmentVariables[key] = Environment.GetEnvironmentVariable(key);
+                Environment.SetEnvironmentVariable(key, value);
+            }
+
+            // Setup MSBuild.
+            ReadOnlySpan<ILogger> binaryLoggers = binaryLogger is null ? [] : [binaryLogger];
+            var projectCollection = new ProjectCollection(
+                GlobalProperties,
+                [.. binaryLoggers, consoleLogger],
+                ToolsetDefinitionLocations.Default);
+            var parameters = new BuildParameters(projectCollection)
+            {
+                Loggers = projectCollection.Loggers,
+                LogTaskInputs = binaryLogger is not null,
+            };
+            BuildManager.DefaultBuildManager.BeginBuild(parameters);
+
+            // Do a restore first (equivalent to MSBuild's "implicit restore", i.e., `/restore`).
+            // See https://github.com/dotnet/msbuild/blob/a1c2e7402ef0abe36bf493e395b04dd2cb1b3540/src/MSBuild/XMake.cs#L1838.
+            var restoreRequest = new BuildRequestData(
+                CreateProjectInstance(projectCollection, addGlobalProperties: static (globalProperties) =>
+                {
+                    globalProperties["MSBuildRestoreSessionId"] = Guid.NewGuid().ToString("D");
+                    globalProperties["MSBuildIsRestoring"] = bool.TrueString;
+                }),
+                targetsToBuild: ["Restore"],
+                hostServices: null,
+                BuildRequestDataFlags.ClearCachesAfterBuild | BuildRequestDataFlags.SkipNonexistentTargets | BuildRequestDataFlags.IgnoreMissingEmptyAndInvalidImports | BuildRequestDataFlags.FailOnUnresolvedSdk);
+            var restoreResult = BuildManager.DefaultBuildManager.BuildRequest(restoreRequest);
+            if (restoreResult.OverallResult != BuildResultCode.Success)
+            {
+                return 1;
+            }
+
+            // Then do a build.
+            var buildRequest = new BuildRequestData(
+                CreateProjectInstance(projectCollection),
+                targetsToBuild: ["Build"]);
+            var buildResult = BuildManager.DefaultBuildManager.BuildRequest(buildRequest);
+            if (buildResult.OverallResult != BuildResultCode.Success)
+            {
+                return 1;
+            }
+
+            BuildManager.DefaultBuildManager.EndBuild();
+            return 0;
+        }
+        catch (Exception e)
+        {
+            Console.Error.WriteLine(e.Message);
+            return 1;
+        }
+        finally
+        {
+            foreach (var (key, value) in savedEnvironmentVariables)
+            {
+                Environment.SetEnvironmentVariable(key, value);
+            }
+
+            binaryLogger?.Shutdown();
+            consoleLogger.Shutdown();
+        }
+
+        static ILogger? GetBinaryLogger(string[] args)
+        {
+            for (int i = args.Length - 1; i >= 0; i--)
+            {
+                var arg = args[i];
+                if (arg.StartsWith("/bl:") || arg.Equals("/bl")
+                    || arg.StartsWith("--binaryLogger:") || arg.Equals("--binaryLogger")
+                    || arg.StartsWith("-bl:") || arg.Equals("-bl"))
+                {
+                    return new BinaryLogger
+                    {
+                        Parameters = arg.IndexOf(':') is >= 0 and var index
+                            ? arg[(index + 1)..]
+                            : "msbuild.binlog",
+                    };
+                }
+            }
+
+            return null;
+        }
+    }
+
+    public ProjectInstance CreateProjectInstance(ProjectCollection projectCollection)
+    {
+        return CreateProjectInstance(projectCollection, addGlobalProperties: null);
+    }
+
+    private ProjectInstance CreateProjectInstance(
+        ProjectCollection projectCollection,
+        Action<IDictionary<string, string>>? addGlobalProperties = null)
+    {
+        var projectRoot = CreateProjectRootElement(projectCollection);
+
+        var globalProperties = projectCollection.GlobalProperties;
+        if (addGlobalProperties is not null)
+        {
+            globalProperties = new Dictionary<string, string>(projectCollection.GlobalProperties, StringComparer.OrdinalIgnoreCase);
+            addGlobalProperties(globalProperties);
+        }
+
+        return ProjectInstance.FromProjectRootElement(projectRoot, new ProjectOptions
+        {
+            GlobalProperties = globalProperties,
+        });
+    }
+
+    private ProjectRootElement CreateProjectRootElement(ProjectCollection projectCollection)
+    {
+        var projectFileFullPath = Path.ChangeExtension(EntryPointFileFullPath, ".csproj");
+        var projectFileText = """
+            <Project>
+                <Import Project="Sdk.props" Sdk="Microsoft.NET.Sdk" />
+
+                <PropertyGroup>
+                    <OutputType>Exe</OutputType>
+                    <TargetFramework>net9.0</TargetFramework>
+                    <ImplicitUsings>enable</ImplicitUsings>
+                    <Nullable>enable</Nullable>
+                </PropertyGroup>
+
+                <Import Project="Sdk.targets" Sdk="Microsoft.NET.Sdk" />
+
+                <!-- Override targets which don't work with project files that are not present on disk. -->
+
+                <Target Name="_FilterRestoreGraphProjectInputItems"
+                        DependsOnTargets="_LoadRestoreGraphEntryPoints"
+                        Returns="@(FilteredRestoreGraphProjectInputItems)">
+                    <ItemGroup>
+                        <FilteredRestoreGraphProjectInputItems Include="@(RestoreGraphProjectInputItems)" />
+                    </ItemGroup>
+                </Target>
+
+                <Target Name="_GetAllRestoreProjectPathItems"
+                        DependsOnTargets="_FilterRestoreGraphProjectInputItems"
+                        Returns="@(_RestoreProjectPathItems)">
+                    <ItemGroup>
+                        <_RestoreProjectPathItems Include="@(FilteredRestoreGraphProjectInputItems)" />
+                    </ItemGroup>
+                </Target>
+
+                <Target Name="_GenerateRestoreGraph"
+                        DependsOnTargets="_FilterRestoreGraphProjectInputItems;_GetAllRestoreProjectPathItems;_GenerateRestoreGraphProjectEntry;_GenerateProjectRestoreGraph"
+                        Returns="@(_RestoreGraphEntry)">
+                    <!-- Output from dependency _GenerateRestoreGraphProjectEntry and _GenerateProjectRestoreGraph -->
+                </Target>
+            </Project>
+            """;
+        ProjectRootElement projectRoot;
+        using (var xmlReader = XmlReader.Create(new StringReader(projectFileText)))
+        {
+            projectRoot = ProjectRootElement.Create(xmlReader, projectCollection);
+        }
+        projectRoot.FullPath = projectFileFullPath;
+        return projectRoot;
+    }
+}

src/Cli/dotnet/commands/dotnet-run/LocalizableStrings.resx

@@ -244,4 +244,10 @@ Make the profile names distinct.</value>
   <data name="LaunchProfileDoesNotExist" xml:space="preserve">
     <value>A launch profile with the name '{0}' doesn't exist.</value>
   </data>
+  <data name="NoTopLevelStatements" xml:space="preserve">
+    <value>Cannot run a file without top-level statements and without a project: '{0}'</value>
+  </data>
+  <data name="RunFileUnsupportedSwitch" xml:space="preserve">
+    <value>The option '{0}' is not supported when running a file without a project: '{1}'</value>
+  </data>
 </root>