Fix #6835 (instantiating a Hackage indefinite package with an inplace package doesn't work)

[ezyang]

Fix #6835

Fixes the bug by accurately tracking when instantiations refer to
inplace packages, and adjusting previously non-inplace packages to be
inplace when this occurs. See comment in ProjectPlanning.hs for more
details.

---

Please include the following checklist in your PR:

• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog.
• The documentation has been updated, if necessary.

Please also shortly describe how you tested your change. Bonus points for added tests!

~/Dev/cabal/dist-newstyle/build/x86_64-osx/ghc-8.10.4/cabal-install-3.5.0.0/x/cabal/build/cabal/cabal test

Also synthetic package tests

[Mikolaj]

@danidiaz: would you like to review this PR?

[ezyang]

CI failures are because I forgot to remove some notice-level debug output

[ezyang]

Now with package tests!

[Mikolaj]

Repeating from IRC:

17:16 < mikolaj_> on another note, we have AppVeyor CI that sometimes fails, nothing unusual, net outages, etc., e.g., here #7413
17:16 < mikolaj_> how do we restart AppVeyor run (I can't, apparently)?
17:17 < mikolaj_> why is it using cabal 2.4.1.0? Generally, what purpose does it server? Just some general Windows testing?

[ezyang]

oh wow, merge requires TWO approving reviews, intruiging

[Mikolaj]

I can't tell I understand all the subtleties here, but LGTM. Thanks a lot of the extensive notes and the test. :)

[fgaz]

[x] Any changes that could be relevant to users have been recorded in the changelog.

I don't see the entry though? @ezyang could you add one in another pr?

[fgaz]

And this is a bugfix so:

@Mergifyio backport 3.6

[mergify]

Command backport 3.6: success

Backports have been created

• #7430 Fix #6835 (instantiating a Hackage indefinite package with an inplace package doesn't work) (backport #7413) has been created for branch 3.6

[ezyang]

I don't see the entry though? @ezyang could you add one in another pr?

Oh do we do bugfixes in changelog? I'll try to remember to do this over the weekend

[emilypi]

Yeah, we do, thanks @ezyang!