Resolve assembly location for SingleFile (#1686)

Author: am11

src/BenchmarkDotNet/Running/BuildPartition.cs

@@ -1,4 +1,6 @@
 using System;
+using System.IO;
+using System.Reflection;
 using BenchmarkDotNet.Characteristics;
 using BenchmarkDotNet.Configs;
 using BenchmarkDotNet.Environments;
@@ -34,7 +36,7 @@ public BuildPartition(BenchmarkBuildInfo[] benchmarks, IResolver resolver)
 
         public IResolver Resolver { get; }
 
-        public string AssemblyLocation => RepresentativeBenchmarkCase.Descriptor.Type.Assembly.Location;
+        public string AssemblyLocation => GetResolvedAssemblyLocation(RepresentativeBenchmarkCase.Descriptor.Type.Assembly);
 
         public string BuildConfiguration => RepresentativeBenchmarkCase.Job.ResolveValue(InfrastructureMode.BuildConfigurationCharacteristic, Resolver);
 
@@ -60,5 +62,10 @@ public BuildPartition(BenchmarkBuildInfo[] benchmarks, IResolver resolver)
         public bool IsCustomBuildConfiguration => BuildConfiguration != InfrastructureMode.ReleaseConfigurationName;
 
         public override string ToString() => RepresentativeBenchmarkCase.Job.DisplayInfo;
+
+        private static string GetResolvedAssemblyLocation(Assembly assembly) =>
+            // in case of SingleFile, location.Length returns 0, so we use GetName() and
+            // manually construct the path.
+            assembly.Location.Length == 0 ? Path.Combine(AppContext.BaseDirectory, assembly.GetName().Name) : assembly.Location;
     }
-}
+}

src/BenchmarkDotNet/Toolchains/CsProj/CsProjGenerator.cs

@@ -35,7 +35,7 @@ public CsProjGenerator(string targetFrameworkMoniker, string cliPath, string pac
 
         protected override string GetBuildArtifactsDirectoryPath(BuildPartition buildPartition, string programName)
         {
-            string assemblyLocation = buildPartition.AssemblyLocation;
+            string assemblyLocation = buildPartition.RepresentativeBenchmarkCase.Descriptor.Type.Assembly.Location;
 
             //Assembles loaded from a stream will have an empty location (https://docs.microsoft.com/en-us/dotnet/api/system.reflection.assembly.location).
             string directoryName = assemblyLocation.IsEmpty() ?