Run ghc-supported-extensions on CI

[sol]

This was part of the pre-flight checklist, which I would like to get rid of.

https://github.com/haskell/cabal/wiki/Making-a-release/_compare/b91547b5d7713283754058ea20152d9e915ba043...2c02bf94536d0669a7742882cb46a97b5eda422c

[ffaf1]

Running cabal check make sense, if something pops up most likely the author changed a .cabal file.

But I wonder: does this?
Are we expecting a contributor to add extensions on top what they are doing (which is 99% unrelated to that)?

[sol]

Adding a new GHC version to the build matrix is a contribution. And I think yes, if somebody adds a new GHC to the build matrix, then they should update the list of extensions.

For other kinds of contributions, this should never fail.

[ffaf1]

That makes sense.

[Mikolaj]

Thank you for that. This would be problematic in the past workflow, where we waited for an alpha GHC release before releasing a corresponding cabal release, because we could use the alpha GHC to run this test, but we would not want to add an alpha GHC to CI (and it would take too long anyway, with lots of random Windows CI errors popping up with new GHC releases back then). However, nowadays we start releasing cabal without waiting for an alpha GHC release, so this check is no longer particularly useful for a cabal release, but it's still useful as a sanity check later on, so running it, in particular, when we add a new GHC to CI is enough.

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-06-16 12:47 UTC · Rule: default
• ❌ Checks failed · on draft merge queue: queuing master (4f927a1) and #11970 together #11975
• 🚫 Left the queue — 2026-06-16 14:23 UTC · at dbde496d245bfafe3b61e8830ebc964b224ce24b

This pull request spent 1 hour 35 minutes 40 seconds in the queue, including 1 hour 24 minutes 20 seconds running CI.

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  • Run ghc-supported-extensions on CI #11970
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  • Run ghc-supported-extensions on CI #11970
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