issue with cabal behavior with a custom Setup.hs

Thomas Lippincott tom.lippincott at
Mon Nov 30 00:53:33 UTC 2015

Hmmm, it does appear to aim at a very similar goal, but that branch only 
builds with old cabal versions, and even though I've made my code 
override the same functions, it still doesn't expose the 
dynamically-generated modules on normal import, only on "cabal repl". 
But I also noticed that "cabal repl" also exposes all the hidden 
modules, so maybe that isn't a good indication...anyways, I'm stumped 
for the moment on why modifying the exposed modules list at the confHook 
stage doesn't get propagated to the later stages.  Like I said, the 
modules do get compiled, just not exposed.

On 11/28/2015 11:14 AM, Adam Bergmark wrote:
> I believe this does the same thing as what you want:
> HTH,
> Adam
> On Sat, Nov 28, 2015 at 4:23 PM, Thomas Lippincott
> <tom.lippincott at <mailto:tom.lippincott at>> wrote:
>     Hello,
>     I'm seeing what I think is some strange (or at least, non-intuitive)
>     behavior in a custom package, and was wondering if someone could
>     point me in the right direction.  Basically, I need the build
>     process to generate some additional exposed modules, i.e. add them
>     to the "exposed-modules" variable, and create the corresponding
>     source files. It's easy to get the list of modules and produce the
>     source files at any point in the build process (I know this is a
>     questionable design, trying to do this as part of Cabal, but suffice
>     it to say there are good arguments on both sides for our particular
>     situation).
>     I'm *so* close to having it working perfectly: in fact, if I run
>     "cabal repl", I get a shell with all the right modules compiled and
>     exposed, so, it should work the same way if it's installed and
>     imported in ghci, right?  Well, when I do that, the auto-generated
>     modules are *not* exposed.  It's clearly generating the source files
>     and compiling them, maybe "cabal install" isn't getting the updated
>     module list or something?  Here's what I'm doing:
>     I override "confHook" to call the original configure function, but
>     then get the list of auto-generated modules and add them to the
>     exposedModules field in the Library structure nested in the
>     LocalBuildInfo structure before returning it.  The idea is that I've
>     intercepted the list of exposed modules as early as possible, and so
>     it's as though the Cabal file had the auto-generated modules listed
>     from the start.  I generate the actual source files by overriding
>     "preBuild".  Nothing else is modified from the default simpleUserHooks.
>     This probably isn't the place for "how do I..." questions, so I'll
>     frame it as: why would "cabal repl" work, and "cabal install" and
>     ghci+import not work?  I apologize if this is an inappropriate place
>     to ask, but there aren't exactly a ton of Cabal experts floating around!
>     Thanks for any help,
>     -Tom
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