Delay invalidating cache and gcroots until print-dev-env call succeeds

[bbenne10]

We currently eagerly invalidate the gcroots and old profile rc, assuming that the devshell is in a usable state.
If this assumption does not hold,
we can invalidate a working state for a broken one.

Here we just delay calling _nix_clean_old_gcroots
until we know that we're in a usable state.

In the case that the flake is in an unusable state, this simply reuses the latest working state.

This should address #412.

[bbenne10]

I haven't looked into test failures, but will when I find a moment.

[Mic92]

@mergify queue

[mergify]

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[Mic92]

@bbenne10 I get the same errors locally. Presumably only present after doing the rebase?

[bbenne10]

I am starting to believe that there's something going wrong with the interaction between the creation of the tmp_profile_rc and the _nix_add_gcroot call which causes direnv exec to exit non-zero. I haven't personally modified this behavior in this MR so I think we've got a longer standing bug, maybe?

I'm looking into it a bit more deeply now.

[bbenne10]

Of course, I post and then figure out the bug.

_nix_clean_old_gcroots removes $tmp_profile. Moving it where I did causes it to remove $tmp_profile in between populating $tmp_profile_rc and the subsequent call to nix build (as part of _nix_add_gcroot), which causes the call to nix build to fail and thus the direnv exec call exits 1. I'll poke around to see how I can resolve this.

[bbenne10]

There we go. Tests are passing now.

I have rebased on #427 to keep in line with the logic and logging changes in there. We should get that merged first.

[Mic92]

@mergify queue

[mergify]

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✅ The pull request has been merged automatically

The pull request has been merged automatically at adeced7