8.8.x change in lookupModule / findModule semantics?

[Tseen She]

Sorry for the spam, but I think this is definitely a bug/regression in
ghc-8.8.1 (still present in 8.8.3).

I don't know which commit introduced the problem, but it seems that
getModSummary is no longer reporting the correct ms_hspp_opts, at least for
an in-memory file but it could also be for a file on disk as well (I
haven't excluded that as a possibility).

Here is my workaround

#if MIN_VERSION_GLASGOW_HASKELL(8,8,1,0)
  dflags <- GHC.getSessionDynFlags
  let file = GHC.ms_hspp_file modSum
  buf <- case GHC.ms_hspp_buf modSum of
        Nothing -> liftIO $ hGetStringBuffer file
        Just b -> pure b
  let pragmas = getOptions dflags buf file
  (dflags', _, _) <- parseDynamicFilePragma dflags pragmas
  let modSum' = modSum { GHC.ms_hspp_opts = dflags' }
#else
  let modSum' = modSum
#endif



On Thu, 27 Feb 2020 at 15:18, Tseen She <ts33n.sh3 at gmail.com> wrote:

> and it looks like the language pragmas slurped from the in-memory buffer
> is empty
>
>   tmod <- GHC.typecheckModule (trace (showGhc . GHC.extensions $
> GHC.ms_hspp_opts modSum) pmod)
>
> gives me [] on 8.8 but is [Off ImplicitPrelude, On PackageImports] on
> 8.6.5... that looks like an 8.8 regression to me.
>
>
> On Thu, 27 Feb 2020 at 15:02, Tseen She <ts33n.sh3 at gmail.com> wrote:
>
>> Quick followup with trace debugging:
>>
>> On Thu, 27 Feb 2020 at 14:50, Tseen She <ts33n.sh3 at gmail.com> wrote:
>>
>>> > typecheckModule will just use the ParsedSource parseModule produced so
>>> it
>>> > shouldn't do any more file reading.
>>>
>>> This is where I am not so sure. I am fairly certain that something has
>>> broken in the typechecking line. I will try again with debug tracing to
>>> confirm what the ParsedSource looks like.
>>>
>>
>> I can confirm that a showPpr on `pm_parsed_source` has the in-memory
>> version.
>>
>> But, perhaps, the problem might be that pragmas are not carried over? In
>> my test the "importsOnly" version of the file is preserving two LANGUAGE
>> pragmas that are necessary in order to parse the imports section (one of my
>> tests uses PackageImports). Just a guess, but does 8.8.x now require more
>> manual passing of the dynflags? This seems like a regression / bug to me
>> but I'd be willing to workaround it if it is an intentional behaviour
>> change.
>>
>>
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