On Mon, 10 Aug 2020, James Cook wrote:
Hi libraries@,
(Let me know if there's a better place for Cabal questions. This list is linked from https://www.haskell.org/cabal/ as a place to ask questions.)
I have a project with lots of modules, and lots of executables that use those modules. How should I structure my .cabal file if I want cabal to only build the common modules once?
I have found I can do it as follows, but I am wondering if there's a way to do it without step 1:
1. Create a "library_src" directory with the source for all the shared modules. Put the source files for the executables somewhere else.
2. Create a .cabal file with one "library" stanza with "hs-source-dirs: library_source", and several executable stanzas.
I use to setup directory 'src' for the library, 'test' for test code and, say, 'example' for executables.
If I leave out step 1 and put all the source files in the same place, then the compiler builds them separately for each executable, and I get a "missing-home-modules" warning.
Is it just a fact of life that I need to separate my source into separate directories if I want this to work properly?
Yes. Problem is, that Cabal calls GHC's 'make' feature and that one searches for appropriate modules in its search path. Btw. you give a Library section a name you get a private sub-library of private modules that can be shared between the public library and e.g. the test suite.