[Haskell-cafe] GHC API: parsing as much as I can

[Artem Pelenitsyn]

Looks like exactly what I need, many thanks!

--
Best, Artem

On Fri, 15 Nov 2019 at 12:16, Matthew Pickering <matthewtpickering at gmail.com>
wrote:

> Hi Artem,
>
> You can look at these functions from ghc-exactprint for inspiration.
>
>
> http://hackage.haskell.org/package/ghc-exactprint-0.6.2/docs/Language-Haskell-GHC-ExactPrint-Parsers.html
>
> Cheers,
>
> Matt
>
> On Fri, Nov 15, 2019 at 4:52 PM Artem Pelenitsyn <a.pelenitsyn at gmail.com>
> wrote:
> >
> > Hello Cafe,
> >
> > I need an advice on how to use GHC API to parse big collections of
> Haskell source files.
> > Say, I want to collect ASTs of everything that is on Hackage.
> > I downloaded the whole Hackage (latest versions only) and have it
> locally now.
> > I tried simple advice found in the Parse module documentation:
> > https://hackage.haskell.org/package/ghc-8.6.5/docs/Parser.html
> >
> >     runParser :: DynFlags -> String -> P a -> ParseResult a
> >     runParser flags str parser = unP parser parseState
> >     where
> >       filename = "<interactive>"
> >       location = mkRealSrcLoc (mkFastString filename) 1 1
> >       buffer = stringToStringBuffer str
> >       parseState = mkPState flags buffer location
> >
> > It mostly works: 75% of .hs files on Hackage seem to parse fine. I
> looked into the rest 25%
> > and noticed that this snippet can't handle files using GHC extensions
> such as RankNTypes,
> > TemplateHaskell, BangPatterns, etc.when given the default DynFlags. This
> leads me to the question of how should I initialize DynFlags?
> >
> > Currently, I use this for getting DynFlags:
> >
> > initDflags :: IO DynFlags
> > initDflags = do
> >     let ldir = Just libdir
> >     mySettings <- initSysTools ldir
> >     myLlvmConfig <- initLlvmConfig ldir
> >     initDynFlags (defaultDynFlags mySettings myLlvmConfig)
> >
> > I understand that simple parsing of individual files can't take into
> account extensions activated inside .cabal files. But I'd expect that it
> should be possible to, at least, consider the extensions mentioned in the
> LANGUAGE pragmas. Currently, this isn't happening. Any suggestions on how
> to achieve this are welcomed. I probably won't get to parsing 100% of
> Hackage, but I'd hope for better than the current 75%.
> >
> > --
> > Best wishes,
> > Artem
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