Should M.E.DependencyModel only target netstandard2.0+ going forward?

[ahsonkhan]

M.E.DependencyModel currently supports several TFMs which means we have to maintain the use of two JSON APIs (System.Text.Json for netstandard2.0+ and Newtonsoft.Json for < netstandard2.0).

https://github.com/dotnet/core-setup/blob/63a01b08e5d1d1a6b8544f598b3d3bda76e6e424/src/managed/Microsoft.Extensions.DependencyModel/Microsoft.Extensions.DependencyModel.csproj#L6

We should consider only targeting netstandard2.0 for the upcoming major release and simplify our dependencies.

VS requires 4.7.2 which is compatible with netstandard2.0.

This effort goes in conjunction with dotnet/announcements#90 and helps remove the dependency on Json.NET more cleanly: https://github.com/dotnet/core-setup/issues/3311

Related PRs:

• Update M.E.DependencyModel to use S.T.Json source for netstandard2.0 core-setup#5009
• [WIP] Update core-setup local tools to use S.T.Json for netstandard2.0 instead core-setup#5010

cc @joshfree, @glennc, @eerhardt, @terrajobst, @jaredpar, @ericstj, @davidfowl, @livarcocc

[terrajobst]

Dropping a platform is a breaking change for your consumers.

For BCL-level packages we generally don't do that. However, we often only have the current source be on latest and harvest the old binaries from the previously uploaded package. This reduces the maintenance burden. We could talk to the NuGet team about generalizing this during pack.

I don't have opinions on whether or not it's acceptable for M.E.DependencyModel. I don't consider DI to be a BCL-level component, so maybe dropping a platform is acceptable here.

[jaredpar]

In case it's relevant Roslyn decided to move to netstandard20 only dropping our netstandard1.3 platforms in the NuPkg. This was a result of VS moving to require net472 hence making netstandard20 an option. The benefits of targeting it were high enough we felt it justified the dropping support for netstandard1.3.

[terrajobst]

The benefits of targeting it were high enough we felt it justified the dropping support for netstandard1.3.

That sounds a like a non-sequitur to me. You can offer .NET Standard 2.0 without dropping 1.x. Presumably your unstated position is that you don't want the support burden of doing both, so if you had to pick only one, you felt justified with choosing 2.0?

[jaredpar]

That sounds a like a non-sequitur to me. You can offer .NET Standard 2.0 without dropping 1.x

Yes / No. Consider that many of our dependencies were moving to netstandard20 exclusively. That forced our hand a bit. But if we had all collectively decided that "hey we want to keep netstandard1.3 around" then as a group we could have all decided to keep it. But we didn't because ...

Presumably your unstated position is that you don't want the support burden of doing both, so if you had to pick only one, you felt justified with choosing 2.0?

Correct. The burden of maintaining netstandard1.1 is quite high in our setup.

[terrajobst]

Correct. The burden of maintaining netstandard1.1 is quite high in our setup.

That's fair.

[eerhardt]

I believe DependencyModel is in a similar position as Roslyn here - the burden of maintaining netstandard1.x and net451 implementations is not worth the value. The main consumers of DependencyModel are ASP.NET and the .NET Core SDK. Neither of those need a netstandard1.x or net451 implementation, AFAIK. (@davidfowl @natemcmaster @nguerrera @dsplaisted - please correct me if I'm wrong). There are other consumers of DependencyModel, one of which is explicitly asking for dropping Newtonsoft as a dependency.

Consider that many of our dependencies were moving to netstandard20 exclusively.

Again, we have the same situation here - we are making DependencyModel depend on the new JSON parsing/writing source package, which is netstandard2.0 exclusive to my knowledge.

---

Unless we get customer feedback that DependencyModel 3.0 must keep targeting net451, and netstandard1.x, I think we are justified in dropping those TFMs and only providing a netstandard2.0 implementation.

[natemcmaster]

Confirming what @eerhardt said - aspnet doesn't need netstandard1.x. I'm in favor of dropping it unless we get real feedback that lower TFMs are important for 3.0.

[nguerrera]

For 3.0+, sdk requires something that is net472 and netcoreapp3.0 compatible. So netstandard2.0 is fine for us too.

[eerhardt]

Setting the milestone to Future as this isn't required for 3.0. However, if someone wanted to do the necessary work for 3.0, we can pull it in to 3.0.

[eerhardt]

I plan on doing this as part of moving Microsoft.Extensions.DependencyModel from src\installer to src\libraries.

We can add back the netstandard1.x targets in the future, if deemed necessary. But please speak up early if you know that only supporting netstandard2.0 is going to be a problem.