Re: Using GHC API with multiple targets

I think this is an ok forum for this kind of question. You could also try the haskell mailing list but I'm not sure if you will get more help tehre. I recently played around with the ghc api and I found the `hint` package to be quite helpful as an example on how to do various things when using the ghc api to implement your own interpreter. Have you tried setting verbose? Perhaps the include dir is relative to the working directory. In that case setting:                   , workingDirectory = Just targetDir                   , importPaths      = [targetDir] ++ importPaths dynflags would mean ghc will search in targetDir/targetDir for Lib/Lib2. Should be easy to say for sure by enabling verbosity and looking at the output. Am 06/02/2023 um 13:42 schrieb Eternal Recursion via ghc-devs:

If this is the wrong forum for this question (which as I think about it, I suppose it is) then redirection to a more appropriate mailing list or forum (or any advice, really) would be appreciated. I just figured this would be the forum with the best understanding of how the GHC API works (and has changed over time), and my longer term goal is indeed to contribute to it after I get past my learning curve.

Sincerely,

Bob

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------- Original Message ------- On Saturday, February 4th, 2023 at 4:04 PM, Eternal Recursion via ghc-devs wrote:

...

Hi Everyone!

I'm new here, trying to learn the GHC API. using 944 with cabal 3.8.1.0.

How do I correctly set a GHC Session's DynFlags (and/or other properties) to ensure local libraries imported by the main target are resolved properly at compile time?

What flags need to be set so that GHC is able to load/analyze/compile all relevant Libraries in a package?

This is my current code:

withPath :: FilePath -> IO () withPath target = do let targetDir = takeDirectory target   let targetFile = takeFileName target listing <- listDirectory targetDir   let imports = filter (\f -> takeExtension f == ".hs") listing   print imports   let moduleName = mkModuleName targetFile   g <- defaultErrorHandler defaultFatalMessager defaultFlushOut     $ runGhc (Just libdir) $ do initGhcMonad (Just libdir) dynflags <- getSessionDynFlags setSessionDynFlags $ dynflags { ghcLink          = LinkInMemory                           , ghcMode          = CompManager                           , backend          = Interpreter                           , mainModuleNameIs = moduleName                           , workingDirectory = Just targetDir                           , importPaths      = [targetDir] ++ importPaths dynflags                           } targets <- mapM (\t -> guessTarget t Nothing Nothing) imports setTargets targets setContext [ IIDecl $ simpleImportDecl (mkModuleName "Prelude") ] load LoadAllTargets liftIO . print . ppr =<< getTargets getModuleGraph putStrLn "Here we go!"   print $ ppr $ mgModSummaries g putStrLn "☝️ "

However, when I run it (passing to example/app/Main.hs, in which directory are Lib.hs and Lib2.hs, the latter being imported into Main), I get:

$cabal run cli -- example/app/Main.hs Up to date ["Main.hs","Lib.hs","Lib2.hs"] [main:Main.hs, main:Lib.hs, main:Lib2.hs] Here we go! [ModSummary {    ms_hs_hash = 23f9c4415bad851a1e36db9d813f34be    ms_mod = Lib,    unit = main    ms_textual_imps = [(, Prelude)]    ms_srcimps = [] }, ModSummary {    ms_hs_hash = e1eccc23af49f3498a5a9566e63abefd    ms_mod = Lib2,    unit = main    ms_textual_imps = [(, Prelude)]    ms_srcimps = [] }, ModSummary {    ms_hs_hash = 5f6751d7f0d5547a1bdf39af84f8c07f    ms_mod = Main,    unit = main    ms_textual_imps = [(, Prelude), (, Lib2)]    ms_srcimps = [] }] ☝

example/app/Main.hs:4:1: error:    Could not find module ‘Lib2’    Use -v (or `:set -v` in ghci) to see a list of the files searched for.  | 4 |import qualified Lib2 as L2  |^^^^^^^^^^^^^^^^^^^^^^^^^^^ cli: example/app/Main.hs:4:1: error:    Could not find module `Lib2'    Use -v (or `:set -v` in ghci) to see a list of the files searched for.

​What do I need to do differently to make this work?

I have a local Cabal file I could use, but to know what I need out of it, I need to understand the minimum required info to get this to work. TIA!

Sincerely,

Bob

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