testsuite: UntrimmedImport test often fails in CI lately

[ulysses4ever]

Describe the bug

/

Error parsing project file https://www.stackage.org/nightly-2024-12-05/cabal.config:9:
 - "<eitherParsec>" (line 2543, column 4):
   unexpected end of input
   expecting ".", ":", white space, "+", "-", opening paren, operator, "installed", "source", "test" or "bench"

...
*** unexpected failure for PackageTests/ProjectImport/UntrimmedImport/cabal.test.hs

Example run: https://github.com/haskell/cabal/actions/runs/14853023896/job/41700087129?pr=10946#step:17:3022

Apparently, this has to do with the recent migration of Stackage and changes in caching of these cabal.config files. @chreekat says it may be commercialhaskell/stackage-server#347

Notes

I don't think it's a good idea to have a test that downloads anything from the Internet. So, instead of "simply" marking it as flaky, we could instead fix it to avoid that.

[geekosaur]

I thought that and then wondered if the test in question is testing download from the Internet? That said, we know that even downloading from GitHub itself is unreliable (causing timeouts that require us to restart CI occasionally), so maybe we should take the hint and minimize the downloads as much as possible and rely on manual testing/QA for those.

[ulysses4ever]

the test in question is testing download from the Internet?

We could discuss specific cases of this but the present test is clearly aimed at something unrelated: it checks that cabal warns about trailing spaces in the import field.

[Mikolaj]

Copying my ping to @philderbeast on Matrix:

Phil de Joux: it's your test: what do you think we should do?
it's nice that it works on the realistic in-the-wild stackage file and it makes it easy to update the test in the future to a newer file, if needed for any reason, but curl or whatever the culprit is, seems to make it flaky

However, Phil may be busy, so let's not block the CI fix on the discussion of how to test the PR in question in the best possible way.

[chreekat]

Looking at the test, the contents of the config file have no impact at all, since the test is testing the project file that imports the config file. As soon as I can figure out how to run tests in Cabal, I'll make a PR that just uses a small, local cabal.config.

I was also able to reproduce some bad cache of that particular file on Stackage.org, so that was definitely what caused the original error.

[chreekat]

The trouble I had running tests is that, from within the cabal-testsuite directory, I was getting this error:

[cabal/cabal-testsuite]$ cabal build cabal-tests
Resolving dependencies...
Error: [Cabal-7107]
Could not resolve dependencies:
[__0] trying: cabal-testsuite-3 (user goal)
[__1] unknown package: Cabal-tests (dependency of cabal-testsuite)
[__1] fail (backjumping, conflict set: Cabal-tests, cabal-testsuite)
After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: cabal-testsuite, Cabal-tests

When I changed up one directory, the command then succeeded. Seems weird to me.

[chreekat]

I opened #10951, but when I run the tests locally, it fails as if the original fix had not been applied.

[philderbeast]

I was able to reproduce this locally with 6953972 5 mins ago but not now, the line number and column are the same as the failure on CI:

$ cabal run cabal-testsuite:cabal-tests -- \
--with-cabal=./dist-newstyle/build/x86_64-linux/ghc-9.10.1/cabal-install-3.15.0.0/x/cabal/build/cabal/cabal cabal-testsuite/PackageTests/ProjectImport/UntrimmedImport/cabal.test.hs
...
Error parsing project file https://www.stackage.org/nightly-2024-12-05/cabal.config:9:
 - "<eitherParsec>" (line 2543, column 4):
   unexpected end of input
   expecting ".", ":", white space, "+", "-", opening paren, operator, "installed", "source", "test" or "bench"

[ulysses4ever]

the test is testing the project file that imports the config file

The catch is that the value of the import field is supposed to be a URL, not a (relative) path, if I understand correctly. @philderbeast is that right?