Scripts without an .hs or .lhs extension no longer work

[ElderEphemera]

Describe the bug
In cabal version 3.6.2.0 and before, scripts could be named anything. But with a cabal-install built from HEAD attempting to run any script file without an ".hs" or ".lhs" suffix fails.

To Reproduce
Save the following as a file named "script":

{- cabal:
build-depends: base
-}

main = putStrLn "Hello"

Then,

$ cabal --version
cabal-install version 3.7
compiled using version 3.7.0.0 of the Cabal library 

$ cabal v2-run script
Resolving dependencies...
Build profile: -w ghc-9.2.1 -O1
In order, the following will be built (use -v for more details):
 - fake-package-0 (exe:script) (first run)
Configuring executable 'script' for fake-package-0..
Error: cabal: The 'main-is' field must specify a '.hs' or '.lhs' file (even if
it is generated by a preprocessor), or it may specify a C/C++/obj-C source
file.

Expected behavior
Scripts should continue to work regardless of what they are named.

Although, it seems like this new behavior has fixed #5702 so error messages no longer confusingly mention "Main.hs". It would be nice to keep the new behavior but without this regression.

System information

• cabal-install version 3.7 (built from commit 7775be8)
• GHC version 9.2.1
• NixOS 21.05

[fgaz]

I think this is due to @bacchanalia's work in #7851

[bacchanalia]

Sorry about that! I'll look into it.