8.8.x change in lookupModule / findModule semantics?

[Daniel Gröber]

Hi,

On Thu, Feb 27, 2020 at 03:43:35PM +0000, Tseen She wrote:
> Sorry for the spam, but I think this is definitely a bug/regression in
> ghc-8.8.1 (still present in 8.8.3).

No worries

> 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).

On a quick testcase I cannot reproduce this behaviour:

    -- $ ghc -package ghc -package ghc-paths TargetContents.hs
    module Main where

    import GHC
    import GHC.Paths (libdir)
    import MonadUtils
    import DynFlags
    import StringBuffer
    import Data.Time.Clock

    main :: IO ()
    main = do
      defaultErrorHandler defaultFatalMessager defaultFlushOut $ do
        runGhc (Just libdir) $ do
          dflags0 <- getSessionDynFlags
          (dflags1, _, _)
              <- parseDynamicFlags dflags0 $ map noLoc ["-package", "base"]
          _ <- setSessionDynFlags dflags1

          t <- liftIO getCurrentTime
          setTargets [Target (TargetFile "Main.hs" Nothing) False (Just (stringToStringBuffer buffer, t)) ]

          _ <- depanal [] False

          ms <- getModSummary (mkModuleName "Main")
          pm <- parseModule ms

          liftIO $ print $ extensions $ ms_hspp_opts ms

          _ <- typecheckModule pm

          return ()

    buffer = "{-# LANGUAGE PackageImports #-}\nimport \"base\" Data.List\nmain = return ()"

Running it it prints the PackageImports ext from the in-memory buffer just
fine:

    $ ghc-8.8.1 -package ghc -package ghc-paths TargetContents.hs
    $ ./TargetContents
    [On PackageImports]

One change in behaviour to note is that when doing this with <8.8 we first
need to create the Main.hs file so GHC doesn't complain about it missing.

Maybe you can fiddle with the test case until it reflects what you're
doing?

--Daniel
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