Allow main-is as autogen-modules in test suites

[ruifengx]

I am using code-generators to automatically generate my test suite. The Main.hs is also generated, I specify main-is: Main.hs, the auto-generated file is picked up by Cabal, and I have no problem running the tests. However, cabal sdist fails for the package, and depending on that package as a source-package via git also fails. Cabal reports (correctly) an error "Main.hs doesn't exist".

I believe the correct way to tell Cabal that Main.hs is auto-generated is to add Main to autogen-modules, but it does not work (as noted in the documentation):

Right now executable:main-is modules are not supported on autogen-modules.

Is there any specific reasons that it is not supported?

---

Meanwhile, I figured out a workaround:

1. Instead of main-is: Main.hs, I specify the following in the Cabal file:

   test-suite doctests
     main-is: DocTests.hs
     hs-source-dirs: test
     other-modules: Main
     autogen-modules: Main

2. I create a dummy main file test/DocTests.hs that forwards to the real auto-generated Main:

   module DocTests (main) where
   import Main qualified
   main :: IO ()
   main = Main.main

However, this seems to be a really roundabout way to specify something trivial. Maybe there is a simpler workaround that I failed to figure out?

[andreasabel]

Have you tried ghc-options: -main-is ...?
See also:

• Complete the documentation of main-is field #10833
• Another module than given in main-is is picked as main module #10832

[ruifengx]

Oops! Thanks for the link. It seems main-is is not doing what I expected it to (in my case, I suspect the generated Main.hs is still chosen as the main module because its name is Main, but it works either way, so it doesn't really matter).

But I still think that is orthogonal to what I report here. The problem is that a test-suite with type exitcode-stdio-1.0 is required to have a main-is field (otherwise the cabal file is considered invalid), so I have to refer to some Main module in my cabal file, and that file cannot be specified as autogen-modules.