Generate the F# file who contains the main (EntryPoint) based on runtime

[enricosada]

F# bundle the Program.fs (who contains the main, [<EntryPoint>] in f#), because a test project targeting netcoreapp2.0 is built as exe (so need a main)
But if i switch to net461, the test project is a library, by design, and should include it.

Atm template is going to be changed to conditionally include the Program.fs (ref dotnet/templating#1271 ) to workaround this.

But that's annoying, because all test framework templates need to do so. otherwise bug is subtle (ref dotnet/netcorecli-fsc#79 ).

C# autogenerate the Program.cs needed in the CoreGenerateProgramFile target.

F# should do the same.

Minor notes:

• need to add the file at end (for f# file order matter, and EntryPoint MUST be the last), so just Compile is not enough (=> require support by f# sdk, like adding CompileLast or CompileMain item)
• need a property to disable this behaviour. For example the expecto test library, used a lot in F#, configure itself in main, so cannot be autogenerated
• something to generate the main empty file, obj/{projectName}.Program.fs (in F# sdk or msbuild sdk or here)
• a feature flag (a property?), so project based on previous template (who add a Program.fs explicit) doesnt break with new sdk version

/cc @dsyme @cartermp @KevinRansom

Environment

dotnet sdk >= 2.0

[ErikSchierboom]

This would be great to have!

[dsyme]

@enricosada Yes indeed!

[ErikSchierboom]

Is there any plan to work on this?

[saul]

Opened #1664 which does this - it's not a lot of work at all.

[ErikSchierboom]

Love it! Thank a ton @saul!