File: MSBuild\BuildHostProcessManager.cs
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Project: src\src\Workspaces\Core\MSBuild\Microsoft.CodeAnalysis.Workspaces.MSBuild.csproj (Microsoft.CodeAnalysis.Workspaces.MSBuild)
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Diagnostics;
using System.IO;
using System.IO.Pipes;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Xml;
using System.Xml.Linq;
using Microsoft.Extensions.Logging;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.MSBuild;
 
internal sealed class BuildHostProcessManager : IAsyncDisposable
{
    private readonly ImmutableDictionary<string, string> _globalMSBuildProperties;
    private readonly ILoggerFactory? _loggerFactory;
    private readonly ILogger? _logger;
    private readonly string? _binaryLogPath;
 
    private readonly SemaphoreSlim _gate = new(initialCount: 1);
    private readonly Dictionary<BuildHostProcessKind, BuildHostProcess> _processes = [];
 
    public BuildHostProcessManager(ImmutableDictionary<string, string>? globalMSBuildProperties = null, string? binaryLogPath = null, ILoggerFactory? loggerFactory = null)
    {
        _globalMSBuildProperties = globalMSBuildProperties ?? ImmutableDictionary<string, string>.Empty;
        _binaryLogPath = binaryLogPath;
        _loggerFactory = loggerFactory;
        _logger = loggerFactory?.CreateLogger<BuildHostProcessManager>();
    }
 
    /// <summary>
    /// Determines the proper host for processing a project, and returns a <see cref="RemoteBuildHost"/> to service questions about that project; if a proper build host
    /// cannot be created for it, another build host is returned to attempt to get useful results.
    /// </summary>
    public async Task<RemoteBuildHost> GetBuildHostWithFallbackAsync(string projectFilePath, CancellationToken cancellationToken)
    {
        var (buildHost, _) = await GetBuildHostWithFallbackAsync(GetKindForProject(projectFilePath), projectFilePath, cancellationToken).ConfigureAwait(false);
        return buildHost;
    }
 
    /// <summary>
    /// Returns the type of build host requested, falling back to another type of build host if it cannot be created. The actual kind of the other build host is returned; the caller can
    /// check if the kinds differ to know if a fallback was performed.
    /// </summary>
    public async Task<(RemoteBuildHost buildHost, BuildHostProcessKind actualKind)> GetBuildHostWithFallbackAsync(BuildHostProcessKind buildHostKind, string projectOrSolutionFilePath, CancellationToken cancellationToken)
    {
        if (buildHostKind == BuildHostProcessKind.Mono && MonoMSBuildDiscovery.GetMonoMSBuildDirectory() == null)
        {
            _logger?.LogWarning($"An installation of Mono could not be found; {projectOrSolutionFilePath} will be loaded with the .NET Core SDK and may encounter errors.");
            buildHostKind = BuildHostProcessKind.NetCore;
        }
 
        var buildHost = await GetBuildHostAsync(buildHostKind, cancellationToken).ConfigureAwait(false);
 
        // If this is a .NET Framework build host, we may not have have build tools installed and thus can't actually use it to build.
        // Check if this is the case. Unlike the mono case, we have to actually ask the other process since MSBuildLocator only allows
        // us to discover VS instances in .NET Framework hosts right now.
        if (buildHostKind == BuildHostProcessKind.NetFramework)
        {
            if (!await buildHost.HasUsableMSBuildAsync(projectOrSolutionFilePath, cancellationToken).ConfigureAwait(false))
            {
                // It's not usable, so we'll fall back to the .NET Core one.
                _logger?.LogWarning($"An installation of Visual Studio or the Build Tools for Visual Studio could not be found; {projectOrSolutionFilePath} will be loaded with the .NET Core SDK and may encounter errors.");
                return (await GetBuildHostAsync(BuildHostProcessKind.NetCore, cancellationToken).ConfigureAwait(false), actualKind: BuildHostProcessKind.NetCore);
            }
        }
 
        return (buildHost, buildHostKind);
    }
 
    public async Task<RemoteBuildHost> GetBuildHostAsync(BuildHostProcessKind buildHostKind, CancellationToken cancellationToken)
    {
        using (await _gate.DisposableWaitAsync(cancellationToken).ConfigureAwait(false))
        {
            if (!_processes.TryGetValue(buildHostKind, out var buildHostProcess))
            {
                var pipeName = Guid.NewGuid().ToString();
                var processStartInfo = CreateBuildHostStartInfo(buildHostKind, pipeName);
 
                var process = Process.Start(processStartInfo);
                Contract.ThrowIfNull(process, "Process.Start failed to launch a process.");
 
                buildHostProcess = new BuildHostProcess(process, pipeName, _loggerFactory);
                buildHostProcess.Disconnected += BuildHostProcess_Disconnected;
 
                // We've subscribed to Disconnected, but if the process crashed before that point we might have not seen it
                if (process.HasExited)
                {
                    buildHostProcess.LogProcessFailure();
                    throw new Exception($"BuildHost process exited immediately with {process.ExitCode}");
                }
 
                _processes.Add(buildHostKind, buildHostProcess);
            }
 
            return buildHostProcess.BuildHost;
        }
    }
 
    internal ProcessStartInfo CreateBuildHostStartInfo(BuildHostProcessKind buildHostKind, string pipeName)
    {
        return buildHostKind switch
        {
            BuildHostProcessKind.NetCore => CreateDotNetCoreBuildHostStartInfo(pipeName),
            BuildHostProcessKind.NetFramework => CreateDotNetFrameworkBuildHostStartInfo(pipeName),
            BuildHostProcessKind.Mono => CreateMonoBuildHostStartInfo(pipeName),
            _ => throw ExceptionUtilities.UnexpectedValue(buildHostKind)
        };
    }
 
    private void BuildHostProcess_Disconnected(object? sender, EventArgs e)
    {
        Contract.ThrowIfNull(sender, $"{nameof(BuildHostProcess)}.{nameof(BuildHostProcess.Disconnected)} was raised with a null sender.");
 
        Task.Run(async () =>
        {
            BuildHostProcess? processToDispose = null;
 
            using (await _gate.DisposableWaitAsync().ConfigureAwait(false))
            {
                // Remove it from our map; it's possible it might have already been removed if we had more than one way we observed a disconnect.
                var existingProcess = _processes.SingleOrNull(p => p.Value == sender);
                if (existingProcess.HasValue)
                {
                    processToDispose = existingProcess.Value.Value;
                    _processes.Remove(existingProcess.Value.Key);
                }
            }
 
            // Dispose outside of the lock (even though we don't expect much to happen at this point)
            if (processToDispose != null)
            {
                processToDispose.LogProcessFailure();
                await processToDispose.DisposeAsync().ConfigureAwait(false);
            }
        });
    }
 
    public async ValueTask DisposeAsync()
    {
        List<BuildHostProcess> processesToDispose;
 
        // Copy the list out while we're in the lock, otherwise as we dispose these events will get fired, which
        // may try to mutate the list while we're enumerating.
        using (await _gate.DisposableWaitAsync().ConfigureAwait(false))
        {
            processesToDispose = [.. _processes.Values];
            _processes.Clear();
        }
 
        foreach (var process in processesToDispose)
            await process.DisposeAsync().ConfigureAwait(false);
    }
 
    private ProcessStartInfo CreateDotNetCoreBuildHostStartInfo(string pipeName)
    {
        var processStartInfo = new ProcessStartInfo()
        {
            FileName = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "dotnet.exe" : "dotnet",
        };
 
        // We need to roll forward to the latest runtime, since the project may be using an SDK (or an SDK required runtime) newer than we ourselves built with.
        // We set the environment variable since --roll-forward LatestMajor doesn't roll forward to prerelease SDKs otherwise.
        processStartInfo.Environment["DOTNET_ROLL_FORWARD_TO_PRERELEASE"] = "1";
        AddArgument(processStartInfo, "--roll-forward");
        AddArgument(processStartInfo, "LatestMajor");
 
        var netCoreBuildHostPath = GetNetCoreBuildHostPath();
 
        AddArgument(processStartInfo, netCoreBuildHostPath);
 
        AppendBuildHostCommandLineArgumentsConfigureProcess(processStartInfo, pipeName);
 
        return processStartInfo;
    }
 
    internal static string GetNetCoreBuildHostPath()
    {
        // The .NET Core build host is deployed as a content folder next to the application into the BuildHost-netcore path
        var buildHostPath = Path.Combine(Path.GetDirectoryName(typeof(BuildHostProcessManager).Assembly.Location)!, "BuildHost-netcore", "Microsoft.CodeAnalysis.Workspaces.MSBuild.BuildHost.dll");
        AssertBuildHostExists(buildHostPath);
        return buildHostPath;
    }
 
    private ProcessStartInfo CreateDotNetFrameworkBuildHostStartInfo(string pipeName)
    {
        var netFrameworkBuildHost = GetDotNetFrameworkBuildHostPath();
        var processStartInfo = new ProcessStartInfo()
        {
            FileName = netFrameworkBuildHost,
        };
 
        AppendBuildHostCommandLineArgumentsConfigureProcess(processStartInfo, pipeName);
 
        return processStartInfo;
    }
 
    private ProcessStartInfo CreateMonoBuildHostStartInfo(string pipeName)
    {
        var processStartInfo = new ProcessStartInfo
        {
            FileName = "mono"
        };
 
        AddArgument(processStartInfo, GetDotNetFrameworkBuildHostPath());
 
        AppendBuildHostCommandLineArgumentsConfigureProcess(processStartInfo, pipeName);
 
        return processStartInfo;
    }
 
    private static string GetDotNetFrameworkBuildHostPath()
    {
        // The .NET Framework build host is deployed as a content folder next to the application into the BuildHost-net472 path
        var netFrameworkBuildHost = Path.Combine(Path.GetDirectoryName(typeof(BuildHostProcessManager).Assembly.Location)!, "BuildHost-net472", "Microsoft.CodeAnalysis.Workspaces.MSBuild.BuildHost.exe");
        AssertBuildHostExists(netFrameworkBuildHost);
        return netFrameworkBuildHost;
    }
 
    private static void AssertBuildHostExists(string buildHostPath)
    {
        if (!File.Exists(buildHostPath))
            throw new Exception(string.Format(WorkspaceMSBuildResources.The_build_host_could_not_be_found_at_0, buildHostPath));
    }
 
    private void AppendBuildHostCommandLineArgumentsConfigureProcess(ProcessStartInfo processStartInfo, string pipeName)
    {
        AddArgument(processStartInfo, "--pipe");
        AddArgument(processStartInfo, pipeName);
 
        foreach (var globalMSBuildProperty in _globalMSBuildProperties)
        {
            AddArgument(processStartInfo, "--property");
            AddArgument(processStartInfo, globalMSBuildProperty.Key + '=' + globalMSBuildProperty.Value);
        }
 
        if (_binaryLogPath is not null)
        {
            AddArgument(processStartInfo, "--binlog");
            AddArgument(processStartInfo, _binaryLogPath);
        }
 
        AddArgument(processStartInfo, "--locale");
        AddArgument(processStartInfo, System.Globalization.CultureInfo.CurrentUICulture.Name);
 
        // MSBUILD_EXE_PATH is read by MSBuild to find related tasks and targets. We don't want this to be inherited by our build process, or otherwise
        // it might try to load targets that aren't appropriate for the build host.
        processStartInfo.Environment.Remove("MSBUILD_EXE_PATH");
 
        processStartInfo.CreateNoWindow = true;
        processStartInfo.UseShellExecute = false;
        processStartInfo.RedirectStandardInput = true;
        processStartInfo.RedirectStandardOutput = true;
        processStartInfo.RedirectStandardError = true;
    }
 
    private static void AddArgument(ProcessStartInfo processStartInfo, string argument)
    {
        // On .NET Core 2.1 and higher we can just use ArgumentList to do the right thing; downlevel we need to manually
        // construct the string
#if NET
        processStartInfo.ArgumentList.Add(argument);
#else
        if (processStartInfo.Arguments.Length > 0)
            processStartInfo.Arguments += ' ';
 
        if (argument.Contains(' '))
            processStartInfo.Arguments += '"' + argument + '"';
        else
            processStartInfo.Arguments += argument;
#endif
    }
 
    private static readonly XmlReaderSettings s_xmlSettings = new()
    {
        DtdProcessing = DtdProcessing.Prohibit,
    };
 
    public static BuildHostProcessKind GetKindForProject(string projectFilePath)
    {
        // In Source Build builds, we don't have a net472 host at all, so the answer is simple. We unfortunately can't create a net472 build because there's no
        // reference assemblies to build against.
#if DOTNET_BUILD_FROM_SOURCE
        return BuildHostProcessKind.NetCore;
#else
 
        // This implements the algorithm as stated in https://github.com/dotnet/project-system/blob/9a761848e0f330a45e349685a266fea00ac3d9c5/docs/opening-with-new-project-system.md;
        // we'll load the XML of the project directly, and inspect for certain elements.
        XDocument document;
 
        var frameworkHostType = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? BuildHostProcessKind.NetFramework : BuildHostProcessKind.Mono;
 
        try
        {
            // Read the XML, prohibiting DTD processing due the the usual security concerns there.
            using var fileStream = FileUtilities.OpenRead(projectFilePath);
            using var xmlReader = XmlReader.Create(fileStream, s_xmlSettings);
            document = XDocument.Load(xmlReader);
        }
        catch (Exception e) when (e is IOException or XmlException)
        {
            // We were unable to read the file; rather than having callers of the build process manager have to deal with this special case
            // we'll instead just give them a host that corresponds to what they are running as; we know that host unquestionably exists
            // and the rest of the code can deal with this cleanly.
#if NET
            return BuildHostProcessKind.NetCore;
#else
            return frameworkHostType;
#endif
        }
 
        // If we don't have a root, doesn't really matter which. This project is just malformed.
        if (document.Root == null)
            return BuildHostProcessKind.NetCore;
 
        // Look for SDK attribute on the root
        if (document.Root.Attribute("Sdk") != null)
            return BuildHostProcessKind.NetCore;
 
        // Look for <Import Sdk=... />
        if (document.Root.Elements("Import").Attributes("Sdk").Any())
            return BuildHostProcessKind.NetCore;
 
        // Look for <Sdk ... />
        if (document.Root.Elements("Sdk").Any())
            return BuildHostProcessKind.NetCore;
 
        // Looking for PropertyGroups that contain TargetFramework or TargetFrameworks nodes
        var propertyGroups = document.Descendants("PropertyGroup");
        if (propertyGroups.Elements("TargetFramework").Any() || propertyGroups.Elements("TargetFrameworks").Any())
            return BuildHostProcessKind.NetCore;
 
        // Nothing that indicates it's an SDK-style project, so use our .NET framework host
        return frameworkHostType;
 
#endif
    }
 
    public enum BuildHostProcessKind
    {
        NetCore,
        NetFramework,
        Mono
    }
 
    private sealed class BuildHostProcess : IAsyncDisposable
    {
        /// <summary>
        /// The time to wait for a named pipe connection to complete for a newly started server
        /// </summary>
        internal const int TimeOutMsNewProcess = 60_000;
 
        private readonly ILogger? _logger;
        private readonly Process _process;
        private readonly RpcClient _rpcClient;
 
        /// <summary>
        /// A string builder where we collect the process log messages, in case we do want to know them if the process crashes.
        /// Reads/writes should be synchronized by locking this object.
        /// </summary>
        private readonly StringBuilder _processLogMessages = new();
 
        private int _disposed = 0;
 
        public BuildHostProcess(Process process, string pipeName, ILoggerFactory? loggerFactory)
        {
            _logger = loggerFactory?.CreateLogger($"BuildHost PID {process.Id}");
            _process = process;
 
            _process.EnableRaisingEvents = true;
            _process.Exited += Process_Exited;
 
            _process.ErrorDataReceived += Process_ErrorDataReceived;
 
            var pipeClient = NamedPipeUtil.CreateClient(".", pipeName, PipeDirection.InOut, PipeOptions.Asynchronous);
            pipeClient.Connect(TimeOutMsNewProcess);
            if (!NamedPipeUtil.CheckPipeConnectionOwnership(pipeClient))
            {
                throw new Exception("Ownership of BuildHost pipe is incorrect.");
            }
 
            _rpcClient = new RpcClient(sendingStream: pipeClient, receivingStream: pipeClient);
            _rpcClient.Start();
            _rpcClient.Disconnected += Process_Exited;
            BuildHost = new RemoteBuildHost(_rpcClient);
 
            // Call this last so our type is fully constructed before we start firing events
            _process.BeginErrorReadLine();
        }
 
        private void Process_Exited(object? sender, EventArgs e)
        {
            Disconnected?.Invoke(this, EventArgs.Empty);
        }
 
        private void Process_ErrorDataReceived(object sender, DataReceivedEventArgs e)
        {
            if (e.Data is not null)
            {
                lock (_processLogMessages)
                    _processLogMessages.AppendLine(e.Data);
 
                _logger?.LogTrace($"Message from Process: {e.Data}");
            }
        }
 
        public RemoteBuildHost BuildHost { get; }
 
        public event EventHandler? Disconnected;
 
        public async ValueTask DisposeAsync()
        {
            // Ensure only one thing disposes; while we disconnect the process will go away, which will call us to do this again
            if (Interlocked.CompareExchange(ref _disposed, value: 1, comparand: 0) != 0)
                return;
 
            // We will call Shutdown in a try/catch; if the process has gone bad it's possible the connection is no longer functioning.
            try
            {
                if (!_process.HasExited)
                {
                    _logger?.LogTrace("Sending a Shutdown request to the BuildHost.");
 
                    await BuildHost.ShutdownAsync(CancellationToken.None).ConfigureAwait(false);
                }
 
                _rpcClient.Shutdown();
 
                _logger?.LogTrace("Process shut down.");
            }
            catch (Exception e)
            {
                _logger?.LogError(e, "Exception while shutting down the BuildHost process.");
 
                // Process may have gone bad, so not much else we can do.
                LogProcessFailure();
                _process.Kill();
            }
        }
 
        public void LogProcessFailure()
        {
            if (_logger == null)
                return;
 
            string processLog;
            lock (_processLogMessages)
                processLog = _processLogMessages.ToString();
 
            if (!_process.HasExited)
                _logger.LogError("The BuildHost process is not responding. Process output:{newLine}{processLog}", Environment.NewLine, processLog);
            else if (_process.ExitCode != 0)
                _logger.LogError("The BuildHost process exited with {errorCode}. Process output:{newLine}{processLog}", _process.ExitCode, Environment.NewLine, processLog);
        }
    }
}