ghc-pkg file conflicts

[chreekat]

Describe the bug I was running cabal on the same project in parallel:

1. One instance was building with --builddir=dist-newstyle [edit: incorrect, see followup comment]
2. One instance was building with --builddir=dist-pure (with different flags)
3. HLS was also running

cabal --builddir=dist-pure -fpure-haskell -j4 build --enable-tests --enable-benchmarks
Build profile: -w ghc-9.2.8 -O1
In order, the following will be built (use -v for more details):
 - text-2.1 (test:tests) (additional components to build)
Preprocessing test suite 'tests' for text-2.1..
Building test suite 'tests' for text-2.1..
cabal --builddir=dist-pure -fpure-haskell -j4 test --test-options=''
Build profile: -w ghc-9.2.8 -O1
In order, the following will be built (use -v for more details):
 - text-2.1 (test:tests) (ephemeral targets)
ghc-pkg: cannot create: /home/b/Projects/usort/usort-web/text-clone/dist-pure/build/x86_64-linux/ghc-9.2.8/text-2.1/t/tests/package.conf.inplace already exists
make: *** [Makefile:36: pure.test] Error 1

I don't know how easy this will be to reproduce, but note that something similar happens often enough on GHC to cause pain. Lots of examples here: https://grafana.gitlab.haskell.org/d/167r9v6nk/ci-spurious-failures?orgId=2&var-types=ghc-pkg_died&var-jobs=All&var-runners=All&from=now-45d&to=now&refresh=15m

To Reproduce :shrug:

Expected behavior Don't make ghc-pkg angry

System information

cabal-install version 3.10.1.0 compiled using version 3.10.1.0 of the Cabal library

The Glorious Glasgow Haskell Compilation System, version 9.2.8

[chreekat]

Oh. I had a typo in my entr script. I actually did have two instances of cabal compiling in the same builddir at the same time. Perhaps this is a known issue.

[geekosaur]

Yes, that's known not to work although it's not well communicated in the documentation and we really should lock dist directories while they're in use.