allow-eval ignores preprocessors

[aavogt]

I have a comment:

{-# OPTIONS_GHC -F -pgmF HListPP #-}
-- $> `blah

This becomes valid syntax if run with HListPP-0.3. But ghcid reads the original file.

Running ghc with -v prints things like

*** Haskell pre-processor:
HListPP Main.hs Main.hs /tmp/ghc19601_0/ghc_1.hspp
compile: input file /tmp/ghc19601_0/ghc_1.hspp

Those hspp files should be read by getCommands ( https://github.com/ndmitchell/ghcid/blob/52883ef368c97b013dad5c9afcf6cd9bdae9875a/src/Session.hs#L157 ) instead. But I'm not sure how to get the hspp file paths.

[ndmitchell]

I'm not sure that getCommands should be reading the preprocessed output. Where that output appears is fiddly. When it appears is undetermined. I think it might just be a consequence of preprocessors that they don't work perfectly with Ghcid and allow-eval stuff.

[aavogt]

Thanks