[mpilgrem]

Template Α: This PR modifies behaviour or interface

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---

See:

• Why is SetupHooks.lhs unsupported? #12473

EDIT: Also warns if both Haskell and literate Haskell files are present and the latter is being ignored, both for Setup and SetupHooks (being the existing behaviour for Setup).

The change to the code follows the pattern of the lines immediately above.

The change to the documentation now distinguishes between a module and its source file.

[ulysses4ever]

Thanks for picking this up! The docs changes are a clear improvement — separating the SetupHooks module from its source file reads much better.

The code change needs one more step, though: as written it finds SetupHooks.lhs but then copies it verbatim to dist-newstyle/.../setup/SetupHooks.hs, so GHC will try to parse the literate source as plain Haskell when it builds the Setup and hooks executables. The Custom branch just above avoids this by running ppUnlit on the .lhs source — we need the same here. Details and a suggestion inline.

The new test also can't see this, since cabal check doesn't go through updateSetupScript (and already accepted SetupHooks.lhs before this PR). A build-based test would catch both the original bug and the unlit issue; see inline.

[ulysses4ever]

Great! Thanks for the quick turnaround!

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-10-26 20:29 UTC · Rule: default · triggered by rule Put pull requests in the rebase+merge queue
• ✅ Checks passed · on draft merge queue: checking #12475 on master (64c2cc0) #12493
• ✅ Merged — 2026-10-26 22:35 UTC · at bc1f17542cb07a9b7bebeedfebf085a7e2d06245 · merge

This pull request spent 2 hours 5 minutes 56 seconds in the queue, including 1 hour 55 minutes 13 seconds running CI.

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  • Fix #12473 cabal-install supports SetupHooks.lhs (literate Haskell) #12475
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  • Fix #12473 cabal-install supports SetupHooks.lhs (literate Haskell) #12475
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