Migrate from MSBuild to Roslyn

[AndreyAkinshin]

Problem

Currently ClassicBuilder uses a combination of BuildManager.DefaultBuildManager and BuildBenchmark.bat for project building. There are a lot of troubles with this approach:

• It is hard to detect correct version of MSBuild
• On Linux and MacOS, it is also hard to detect correct version of XBuild
• It is impossible to move a benchmark runner to another machine without installed MSBuild/XBuild.

Suggestion

There is a cool NuGet package Microsoft.Net.Compilers which contains full Roslyn compiler (csc.exe + additional dll files). Yep, it is a dependency, but It is not too terrible. Benefits of the suggested approach:

• We shouldn't detect MSBuild/XBuild
• We can run benchmark without installed MSBuild/XBuild
• We even shouldn't generate csproj
• We always have good stable compiler, we don't depend on user environment
• It is a cross-platform way.

@adamsitnik, @mattwarren, what do you think?

[adamsitnik]

@AndreyAkinshin To be honest it sounds great! The only disadvantage I see right now is .NET 4.5+ support which means that we have to drop .NET 4.0 support. But on the other hand this should not be a big deal since most people that write benchmarks know that each .NET framework release brings performance updates and they are up to date.

I am going to spend few hours at the airports tomorrow and think more about this!

[AndreyAkinshin]

Yes, you need installed .NET 4.5 (or mono) but only for compiling. You still can target your benchmark methods to .NET 4.0.

[mattwarren]

Yeah I like this idea, it's the approach that I originally took with MiniBench before I stopped that and started working with you on BenchmarkDotNet.

I agree with @adamsitnik, the only issue I can see is that it forces people to have .NET 4.5 when building the benchmarks, but as he says, that's probably only a small amt of users.

BTW you should take a look at CodeGenerator.cs, it's using Roslyn directly, but should give you some ideas.

[damageboy]

Wouldn't you like to also take a dependency on a MSBuild nuget package while at it? Or is xbuild now considered safe enough?

[AndreyAkinshin]

@damageboy, I don't want to have the MSBuild dependency. I want to compile Program.cs by Roslyn.

[damageboy]

Understood, so you want to abolish the current build generators and go straight to the compiler?

[AndreyAkinshin]

I think, we will keep current toolchain system. We should just write another Builder (e.g. RoslynBuilder instead of ClassicBuilder which based on MSBuild).