Concatenation of mains from conditional branches

[georgefst]

I have an executable which requires slightly different top-level code on different platforms. I have:

    if os(windows)
        main-is: Windows.hs
    if os(linux)
        main-is: Linux.hs

which I thought was a relatively nice solution, but unfortunately I get the rather nonsensical error:

cabal: Windows.hsLinux.hs doesn't exist

Obviously there are various ways to work around this, but it would be great if it just worked.

[georgefst]

Investigating slightly further:

• This actually works fine with repl, build, run, but not install.
• The lack of an 'else' branch isn't the problem - changing if os(linux) to else makes no difference.
• Neither is the mismatch of file and module name - changing everything to Main.hs just gives cabal: Main.hsMain.hs doesn't exist.

[phadej]

Duplicate of #3313

A workaround is to have dummy Main.is

module Main (main) where
import RealMain (main)

and put RealMains into different source-directories:

main-is: Main.hs

-- most sources are here
hs-source-dirs: src/

-- but RealMain has multiple implementations:
if os(windows)
  hs-source-dirs: windows/
If os(linux)
  hs-source-dirs: linux/

other-modules: RealMain

...

[georgefst]

Ah thanks, I did do a quick search but missed that one somehow.