[Haskell-cafe] GHC API arguments via cabal/stack?

[Matthew Pickering]

It is quite hacky but if I want to get access to a typechecked module,
I usually modify haddock and then invoke my analysis with "cabal
haddock --haddock-options="--my-flag". That saves me the pain of
having the deal with manually getting the paths to this stuff.

On Fri, Mar 11, 2016 at 9:27 AM, David Turner
<dct25-561bs at mythic-beasts.com> wrote:
> Hi all,
>
> I'm working on a little program that uses GHC as a library to do some static
> analysis on a project I'm working on. It runs things as far as the
> typechecker (so there's no Template Haskell remaining) and then does the
> analysis on the resulting AST.
>
> Here is how I'm calling GHC at the moment:
>
> runAnalyser :: FilePath -> [String] -> [String] -> IO [(Module, [Fact],
> [Assertion])]
> runAnalyser srcDir args modules = do
>   defaultErrorHandler defaultFatalMessager defaultFlushOut $ do
>       runGhc (Just libdir) $ do
>         dflags <- getSessionDynFlags
>         (dflags', leftover, warnings) <- parseDynamicFlagsCmdLine dflags
>                                           (map noLoc $ args ++ modules)
>         setSessionDynFlags dflags'
>         setTargets =<< forM modules (\exampleModule ->
>           guessTarget (exampleModuleFile srcDir exampleModule) Nothing)
>         load LoadAllTargets
>
>         execWriterT $ forM_ modules $ \exampleModule -> do
>           modSum <- lift $ getModSummary $ mkModuleName exampleModule
>           p <- lift $ parseModule modSum
>           t <- lift $ typecheckModule p
>           case tm_renamed_source t of
>             Nothing -> return ()
>             Just (hsGroup, _, _, _) -> do
>               assertions <- liftIO $ loadAssertions
>                           $ exampleModuleFile srcDir exampleModule
>               let mod = ms_mod $ pm_mod_summary $ tm_parsed_module t
>               tell [( mod
>                     , runFactM (moduleName mod) (facts hsGroup)
>                     , assertions)]
>
>
> The problem I'm currently facing is that this requires me to pass in the
> arguments to GHC, including where all the package databases are and all the
> package ids that stack has decided to use. So far, I've just copy-pasted
> this from the stack log and hard-coded it, but that's clearly not a good
> long-term solution.
>
> I've half-heartedly tried to fool stack into running my analyser as the
> compiler, but stack calls ghc more times than just the one call that I need
> the arguments from. I could make it pass through to the real ghc but this
> feels like piling hacks on top of hacks.
>
> I've also briefly contemplated using the Cabal library to read my .cabal
> file and work out what to do, but I'm unsure that this would work nicely
> under stack. At least, I'm not sure quite what to do with all the package
> databases and other stuff that stack does for you.
>
> Is there a sensible and robust way to get these args as stack would make
> them?
>
> Many thanks,
>
> David
>
>
>
>
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