[CI] All PRs fail on docfx check

[AlexanderWert]

Area(s)

No response

What happened?

PR builds fail on the docfx job (even PRs that succeeded before, if rerunning that job), with the following error message:

Something is wrong with the installation step of docfx.

Semantic convention version

N/A

Additional context

No response

[gregkalapos]

It seems this step fetches docfx v. 3.0 from a custom NuGet feed. V3 has never been publically released, on public NuGet the latest version is v2.76.0. It seems now there is nothing behind this custom NuGet feed from https://docfx.pkgs.visualstudio.com/docfx/. They have a v3 branch (last commit 2 years ago), I suspect it's a build from that branch.

Here is a super old discussion about v3 release: dotnet/docfx#7050.

The step runs docfx build --dry-run, which doesn't seem to be present in 2.x, only in 3.x.

[lmolkova]

FYI: dotnet/docfx#9901

[lmolkova]

Thanks to @jsuereth docfx check is not required and we can merge PRs despite it showing errors until we figure out what to do with it.