Loading a typechecked module and then using it immediately as a package

[Erdi, Gergo]

PUBLIC

Hi,

I have the following to .hs files:


  1.  MyLib.hs:

module MyLib where
...

  2.  Test.hs:

{-# LANGUAGE PackageImports  #-}
module Test where
import "my-pkg" MyLib
...

I would like to parse/typecheck/load MyLib.hs into some Unit "my-unit", then add that to the package "my-pkg", and then typecheck Test.hs, all in-proc using the GHC API, without putting any other files on disk. How do I do that?

What I tried is loading MyLib.hs after setting the homeUnitId in the DynFlags to "my-unit", then editing the packageNameMap in the unitState of the DynFlags to may "my-pkg" to "my-unit":

setHomeUnit :: (GhcMonad m) => UnitId -> m ()
setHomeUnit unitId = do
    dflags <- getSessionDynFlags
    modifySession $ \h -> h{ hsc_dflags = dflags{ homeUnitId = unitId } }

registerUnit :: (GhcMonad m) => PackageName -> UnitId -> m ()
registerUnit pkg unitId = modifySession $ \h -> h{ hsc_dflags = addUnit $ hsc_dflags h }
  where
    addUnit dflags = dflags
        { unitState = let us = unitState dflags in us
            { packageNameMap = M.insert pkg (Indefinite unitId Nothing) $ packageNameMap us
            }
        }

pipeline = do
        setHomeUnit myUnit
        loadModule =<< typecheckModule =<< parseModule =<< modSumarryFor "MyLib"
        registerUnit myPkg myUnit

        setHomeUnit mainUnitId
        typecheckModule =<< parseModule =<< modSumarryFor "Test"


Alas, this doesn't work: the import of `MyLib` from `my-pkg` fails with:

input/linking/Test.hs:5:1: error:
    Could not find module 'MyLib'
    It is not a module in the current program, or in any known package.

TBH I'm not very surprised that it didn't work - that registerUnit function is doing some pretty deep surgery on the unitState that probably breaks several invariants. Still, I wasn't able to find a better way - all the functions in GHC.Unit.State seem to be for querying only.

Thanks,
            Gergo

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