newSession gone from GHC API

[Claus Reinke]

>I just noticed that newSession has been removed from the GHC API.
>Unfortunately, this breaks nearly all examples on the web:
>http://www.haskell.org/haskellwiki/GHC/As_a_library
>http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/API
>Could someone fix those up, to show the new style of interaction? Also
>are the breaking changes to newSession in GHC 6.10, or only in GHC Head?

Thomas said he was working on a conversion guide, but
delayed by travelling:

http://www.haskell.org/pipermail/cvs-ghc/2008-September/045361.html

Meanwhile, since you're somewhat familar with haddock, his
patches to port haddock to the new api may help (I used them
to figure out where to look for more info;). Or, if you prefer
smaller examples, have a look at 

http://www.cs.kent.ac.uk/~cr3/toolbox/haskell/syb-utils/examples/GhcApiSybTesting.hs

which I patched recently (diff below). Mostly, you'll be looking for
runGhc, dropping session parameters, changing dynamic flags from
String to Located String, and splitting checkModule into separate
phases (there's a class that simplifies access via the old record 
selector functions). Possibly other small things, like using liftIO to
do IO in the Ghc monads.

Hth,
Claus

$ darcs changes -v -p 'new Ghc Api' | sed 's/\[_.._\]\[_._\]$//'
diffing dir...
Mon Sep 22 20:01:02 GMT Daylight Time 2008  claus.reinke at talk21.com
  * adapt example to new Ghc Api
    {
    hunk ./examples/GhcApiSybTesting.hs 15
    +import SrcLoc
    +import MonadUtils
    hunk ./examples/GhcApiSybTesting.hs 35
    -main = defaultErrorHandler defaultDynFlags $ do
    -  s           <- newSession (Just libdir)
    -  flags       <- getSessionDynFlags s
    -  (flags,_,_) <- parseDynamicFlags flags ["-package ghc"]
    +main = defaultErrorHandler defaultDynFlags $
    +       runGhc (Just libdir) $ do
    +  flags       <- getSessionDynFlags
    +  (flags,_,_) <- parseDynamicFlags flags [noLoc "-package ghc"]
    hunk ./examples/GhcApiSybTesting.hs 40
    -    setSessionDynFlags s flags{ hscTarget=HscInterpreted }
    -    addTarget s =<< guessTarget source Nothing
    -    load s LoadAllTargets
    -    unqual  <- getPrintUnqual s
    +    setSessionDynFlags flags{ hscTarget=HscInterpreted }
    +    addTarget =<< guessTarget source Nothing
    +    load LoadAllTargets
    +    unqual  <- getPrintUnqual
    +    {-
    hunk ./examples/GhcApiSybTesting.hs 50
    +    -}
    +    tcm <- typecheckModule =<< parseModule (mkModuleName modName)
    +    doSomething unqual tcm
    hunk ./examples/GhcApiSybTesting.hs 63
    -        doSomething unqual cm = do
    -          let parsed            = parsedSource cm
    -              renamed           = renamedSource cm
    -              typechecked       = typecheckedSource cm
    +        doSomething unqual tcm = liftIO $ do
    +          let parsed            = parsedSource tcm
    +              renamed           = renamedSource tcm
    +              typechecked       = typecheckedSource tcm
    hunk ./examples/GhcApiSybTesting.hs 84
    -          maybe (putStrLn "no typechecked source")
    -                (printForUser stdout unqual . shown TypeChecker) typechecked
    +          printForUser stdout unqual $ shown TypeChecker typechecked
    }