Split builds into 2 steps to gather assembly references.

src/BenchmarkDotNet/Diagnosers/PerfCollectProfiler.cs

@@ -229,6 +229,7 @@ private void EnsureSymbolsForNativeRuntime(DiagnoserActionParameters parameters)
             // We install the tool in a dedicated directory in order to always use latest version and avoid issues with broken existing configs.
             string toolPath = Path.Combine(Path.GetTempPath(), "BenchmarkDotNet", "symbols");
             DotNetCliCommand cliCommand = new (
+                csProjPath: string.Empty,
                 cliPath: cliPath,
                 arguments: $"tool install dotnet-symbol --tool-path \"{toolPath}\"",
                 generateResult: null,

src/BenchmarkDotNet/Toolchains/ArtifactsPaths.cs

@@ -4,7 +4,7 @@ namespace BenchmarkDotNet.Toolchains
 {
     public class ArtifactsPaths
     {
-        public static readonly ArtifactsPaths Empty = new ArtifactsPaths("", "", "", "", "", "", "", "", "", "", "", "");
+        public static readonly ArtifactsPaths Empty = new ("", "", "", "", "", "", "", "", "", "", "", "", "");
 
         [PublicAPI] public string RootArtifactsFolderPath { get; }
         [PublicAPI] public string BuildArtifactsDirectoryPath { get; }
@@ -13,6 +13,7 @@ public class ArtifactsPaths
         [PublicAPI] public string ProgramCodePath { get; }
         [PublicAPI] public string AppConfigPath { get; }
         [PublicAPI] public string NuGetConfigPath { get; }
+        [PublicAPI] public string BuildForReferencesProjectFilePath { get; }
         [PublicAPI] public string ProjectFilePath { get; }
         [PublicAPI] public string BuildScriptFilePath { get; }
         [PublicAPI] public string ExecutablePath { get; }
@@ -27,6 +28,7 @@ public ArtifactsPaths(
             string programCodePath,
             string appConfigPath,
             string nuGetConfigPath,
+            string buildForReferencesProjectFilePath,
             string projectFilePath,
             string buildScriptFilePath,
             string executablePath,
@@ -40,6 +42,7 @@ public ArtifactsPaths(
             ProgramCodePath = programCodePath;
             AppConfigPath = appConfigPath;
             NuGetConfigPath = nuGetConfigPath;
+            BuildForReferencesProjectFilePath = buildForReferencesProjectFilePath;
             ProjectFilePath = projectFilePath;
             BuildScriptFilePath = buildScriptFilePath;
             ExecutablePath = executablePath;

src/BenchmarkDotNet/Toolchains/CsProj/CsProjGenerator.cs

@@ -61,37 +61,64 @@ protected override string GetBuildArtifactsDirectoryPath(BuildPartition buildPar
         protected override string GetProjectFilePath(string buildArtifactsDirectoryPath)
             => Path.Combine(buildArtifactsDirectoryPath, "BenchmarkDotNet.Autogenerated.csproj");
 
+        protected override string GetProjectFilePathForReferences(string buildArtifactsDirectoryPath)
+            => Path.Combine(buildArtifactsDirectoryPath, "BenchmarkDotNet.Autogenerated.ForReferences.csproj");
+
         protected override string GetBinariesDirectoryPath(string buildArtifactsDirectoryPath, string configuration)
             => Path.Combine(buildArtifactsDirectoryPath, "bin", configuration, TargetFrameworkMoniker);
 
         protected override string GetIntermediateDirectoryPath(string buildArtifactsDirectoryPath, string configuration)
             => Path.Combine(buildArtifactsDirectoryPath, "obj", configuration, TargetFrameworkMoniker);
 
         [SuppressMessage("ReSharper", "StringLiteralTypo")] // R# complains about $variables$
-        protected override void GenerateProject(BuildPartition buildPartition, ArtifactsPaths artifactsPaths, ILogger logger)
-        {
-            var benchmark = buildPartition.RepresentativeBenchmarkCase;
-            var projectFile = GetProjectFilePath(benchmark.Descriptor.Type, logger);
-
-            var xmlDoc = new XmlDocument();
-            xmlDoc.Load(projectFile.FullName);
-            var (customProperties, sdkName) = GetSettingsThatNeedToBeCopied(xmlDoc, projectFile);
-
-            var content = new StringBuilder(ResourceHelper.LoadTemplate("CsProj.txt"))
+        private string LoadCsProj(BuildPartition buildPartition, ArtifactsPaths artifactsPaths, string projectFile, string customProperties, string sdkName)
+            => new StringBuilder(ResourceHelper.LoadTemplate("CsProj.txt"))
                 .Replace("$PLATFORM$", buildPartition.Platform.ToConfig())
                 .Replace("$CODEFILENAME$", Path.GetFileName(artifactsPaths.ProgramCodePath))
-                .Replace("$CSPROJPATH$", projectFile.FullName)
+                .Replace("$CSPROJPATH$", projectFile)
                 .Replace("$TFM$", TargetFrameworkMoniker)
                 .Replace("$PROGRAMNAME$", artifactsPaths.ProgramName)
-                .Replace("$RUNTIMESETTINGS$", GetRuntimeSettings(benchmark.Job.Environment.Gc, buildPartition.Resolver))
+                .Replace("$RUNTIMESETTINGS$", GetRuntimeSettings(buildPartition.RepresentativeBenchmarkCase.Job.Environment.Gc, buildPartition.Resolver))
                 .Replace("$COPIEDSETTINGS$", customProperties)
                 .Replace("$CONFIGURATIONNAME$", buildPartition.BuildConfiguration)
                 .Replace("$SDKNAME$", sdkName)
                 .ToString();
 
+        protected override void GenerateProject(BuildPartition buildPartition, ArtifactsPaths artifactsPaths, ILogger logger)
+        {
+            var projectFile = GetProjectFilePath(buildPartition.RepresentativeBenchmarkCase.Descriptor.Type, logger);
+
+            var xmlDoc = new XmlDocument();
+            xmlDoc.Load(projectFile.FullName);
+            var (customProperties, sdkName) = GetSettingsThatNeedToBeCopied(xmlDoc, projectFile);
+
+            GenerateBuildForReferencesProject(buildPartition, artifactsPaths, projectFile.FullName, customProperties, sdkName);
+
+            var content = LoadCsProj(buildPartition, artifactsPaths, projectFile.FullName, customProperties, sdkName);
+
             File.WriteAllText(artifactsPaths.ProjectFilePath, content);
         }
 
+        protected void GenerateBuildForReferencesProject(BuildPartition buildPartition, ArtifactsPaths artifactsPaths, string projectFile, string customProperties, string sdkName)
+        {
+            var content = LoadCsProj(buildPartition, artifactsPaths, projectFile, customProperties, sdkName);
+
+            // We don't include the generated .notcs file when building the reference dlls, only in the final build.
+            var xmlDoc = new XmlDocument();
+            xmlDoc.Load(new StringReader(content));
+            XmlElement projectElement = xmlDoc.DocumentElement;
+            projectElement.RemoveChild(projectElement.SelectSingleNode("ItemGroup/Compile").ParentNode);
+
+            var startupObjectElement = projectElement.SelectSingleNode("PropertyGroup/StartupObject");
+            startupObjectElement.ParentNode.RemoveChild(startupObjectElement);
+
+            // We need to change the output type to library since we're only compiling for dlls.
+            var outputTypeElement = projectElement.SelectSingleNode("PropertyGroup/OutputType");
+            outputTypeElement.InnerText = "Library";
+
+            xmlDoc.Save(artifactsPaths.BuildForReferencesProjectFilePath);
+        }
+
         /// <summary>
         /// returns an MSBuild string that defines Runtime settings
         /// </summary>

src/BenchmarkDotNet/Toolchains/DotNetCli/DotNetCliBuilder.cs

@@ -1,4 +1,6 @@
 using System;
+using System.IO;
+using System.Xml;
 using BenchmarkDotNet.Jobs;
 using BenchmarkDotNet.Loggers;
 using BenchmarkDotNet.Running;
@@ -25,22 +27,69 @@ public DotNetCliBuilder(string targetFrameworkMoniker, string? customDotNetCliPa
 
         public BuildResult Build(GenerateResult generateResult, BuildPartition buildPartition, ILogger logger)
         {
-            BuildResult buildResult = new DotNetCliCommand(
-                    CustomDotNetCliPath,
-                    string.Empty,
-                    generateResult,
-                    logger,
-                    buildPartition,
-                    Array.Empty<EnvironmentVariable>(),
-                    buildPartition.Timeout,
-                    logOutput: LogOutput)
+            var cliCommand = new DotNetCliCommand(
+                generateResult.ArtifactsPaths.BuildForReferencesProjectFilePath,
+                CustomDotNetCliPath,
+                string.Empty,
+                generateResult,
+                logger,
+                buildPartition,
+                Array.Empty<EnvironmentVariable>(),
+                buildPartition.Timeout,
+                logOutput: LogOutput);
+
+            BuildResult buildResult;
+            // Integration tests are built without dependencies, so we skip the first step.
+            if (!buildPartition.ForcedNoDependenciesForIntegrationTests)
+            {
+                // We build the original project first to obtain all dlls.
+                buildResult = cliCommand.RestoreThenBuild();
+
+                if (!buildResult.IsBuildSuccess)
+                    return buildResult;
+
+                // After the dlls are built, we gather the assembly references, then build the benchmark project.
+                GatherReferences(generateResult.ArtifactsPaths);
+            }
+
+            buildResult = cliCommand.WithCsProjPath(generateResult.ArtifactsPaths.ProjectFilePath)
                 .RestoreThenBuild();
+
             if (buildResult.IsBuildSuccess &&
                 buildPartition.RepresentativeBenchmarkCase.Job.Environment.LargeAddressAware)
             {
                 LargeAddressAware.SetLargeAddressAware(generateResult.ArtifactsPaths.ExecutablePath);
             }
             return buildResult;
         }
+
+        internal static void GatherReferences(ArtifactsPaths artifactsPaths)
+        {
+            var xmlDoc = new XmlDocument();
+            xmlDoc.Load(artifactsPaths.ProjectFilePath);
+            XmlElement projectElement = xmlDoc.DocumentElement;
+
+            // Add reference to every dll.
+            var itemGroup = xmlDoc.CreateElement("ItemGroup");
+            projectElement.AppendChild(itemGroup);
+            foreach (var assemblyFile in Directory.GetFiles(artifactsPaths.BinariesDirectoryPath, "*.dll"))
+            {
+                var assemblyName = Path.GetFileNameWithoutExtension(assemblyFile);
+                // The dummy csproj was used to build the original project, but it also outputs a dll for itself which we need to ignore because it's not valid.
+                if (assemblyName == artifactsPaths.ProgramName)
+                {
+                    continue;
+                }
+                var referenceElement = xmlDoc.CreateElement("Reference");
+                itemGroup.AppendChild(referenceElement);
+                referenceElement.SetAttribute("Include", assemblyName);
+                var hintPath = xmlDoc.CreateElement("HintPath");
+                referenceElement.AppendChild(hintPath);
+                var locationNode = xmlDoc.CreateTextNode(assemblyFile);
+                hintPath.AppendChild(locationNode);
+            }
+
+            xmlDoc.Save(artifactsPaths.ProjectFilePath);
+        }
     }
 }