Make VS2019 a prerequisite, and add scripts to set required env vars

[natemcmaster]

Changes:

• Update Extensions.sln to require VS 2019.
• Add two scripts (inspired by Python's virtualenv) which set required environment variables so you can use dotnet and launch VS Code on command line. I did this because Arcade puts dotnet core in "$repoRoot/.dotnet" by default now.

[ryanbrandenburg]

Code looks good, if you've tested locally.

[dougbu]

For an individual user building locally, don't we want $env:UserProfile\.dotnet? This seems to require re-activating whenever a dev moves from their aspnet/Extensions repo to aspnet/AspNetCore and back.

[natemcmaster]

For an individual user building locally, don't we want $env:UserProfile.dotnet?

I wish that were the case, but that's not the default Arcade chose. Aracde installs to "$repoRoot/.dotnet". So yes, you have to reactivate to update PATH when moving between repos. 😞

[dougbu]

Should the requirement also be included in global.json?

[natemcmaster]

AFAIK the only thing Visual Studio and dotnet.exe reads from global.json is SDK version. The other data in that file is used by other tooling and scripts, like MSBuild and Arcade.

https://github.com/aspnet/Extensions/blob/8535a13651cde6d28ee7059c7d8e5ecb5f384f42/global.json#L2-L4

[Eilon]

Don't know what the code does, but the concept looks good. Docs look good too.

[poke]

@natemcmaster Hey, I was wondering if the VS 2019 requirement is a hard requirement, or if there was a way to get this into a buildable state with VS 2017 too. I tried lowering the requirement in the sln and was able to load the solution properly but then I got an error that the “current .NET SDK does not support targeting .NET Standard 2.0.” I did activate the environment for VS, so the 3.0 SDK should be there?

The reason I’m asking is because I don’t really want to waste another 5+ gigabytes on multiple machines for a VS that I’m not going to use otherwise. And I have been able to use 2017 for both Extensions and AspNetCore just fine before the move to Arcade. I just called build.ps1 back then and launched VS from the console to inherit the environment variables the build script set up.

[natemcmaster]

I was wondering if the VS 2019 requirement is a hard requirement,

Yes, it is. We are also updating AspNetCore to require VS2019. (see dotnet/aspnetcore#7005)