stack ghci doesn't see preprocessed (e.g. c2hs) files, and doesn't error

[mtolly]

Steps to reproduce:

$ stack --version
Version 0.1.1.0, Git revision bf086c6d5f8e86e95f161c38c596a6dae571ab65

pkg-a.cabal:

name:                pkg-a
version:             0.1.0.0
build-type:          Simple
cabal-version:       >= 1.10

library
  exposed-modules:     A
  build-depends:       base >= 4.7 && < 5
  default-language:    Haskell2010

A.chs:

module A where

stack.yaml:

flags: {}
packages:
- '.'
extra-deps: []
resolver: nightly-2015-06-28

Expected:

Running stack ghci builds and loads module A (after preprocessing with c2hs).

Actual:

$ stack ghci
Configuring GHCi with the following packages: pkg-a
GHCi, version 7.10.1: http://www.haskell.org/ghc/  :? for help
Prelude λ import A

<no location info>:
    Could not find module ‘A’
    It is not a module in the current program, or in any known package.
Prelude λ

# ok, let's install it into stack work
$ stack build
pkg-a-0.1.0.0: build
Building pkg-a-0.1.0.0...
Preprocessing library pkg-a-0.1.0.0...
[1 of 1] Compiling A                ( .stack-work/dist/x86_64-osx/Cabal-1.22.2.0/build/A.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.2.0/build/A.o )
In-place registering pkg-a-0.1.0.0...
pkg-a-0.1.0.0: install
Installing library in
/Users/mtolly/git/stackbugs/.stack-work/install/x86_64-osx/nightly-2015-06-28/7.10.1/lib/x86_64-osx-ghc-7.10.1/pkga_9rCkBC6ycwY3RIqsB0Qe80
Registering pkg-a-0.1.0.0...

$ stack ghci
Configuring GHCi with the following packages: pkg-a
GHCi, version 7.10.1: http://www.haskell.org/ghc/  :? for help
Prelude λ import A

<no location info>:
    Could not find module ‘A’
    It is a member of the hidden package ‘pkg-a-0.1.0.0@pkga_9rCkBC6ycwY3RIqsB0Qe80’.
Prelude λ

# this loads the installed (in stack work) package, not the current source
$ stack ghci --ghc-options "-package pkg-a"
Configuring GHCi with the following packages: pkg-a
GHCi, version 7.10.1: http://www.haskell.org/ghc/  :? for help
Prelude λ import A
Prelude A λ
Leaving GHCi.

Actually you'll get this result if the A file is named anything other than A.hs (like A.foobar), or even if it doesn't exist at all.

So there are 2 bugs:

1. Module A is not loaded when it's a non-.hs extension
2. The fact that module A wasn't found while supposedly loading pkg-a does not cause an error

[ntc2]

I might be running into something similar: stack ghci is failing to find files generated by Alex and Happy in a dependency package, elf:

[...]
Loading package elf-0.28 ... linking ... done.
[...]
Loading package flexdis86-0.1.1 ... linking ... done.
[...]

/home/conathan/cfar/reopt.git/deps/elf/src/Data/Elf/TH.hs:3:8:
    Could not find module ‘Data.Elf.Lexer’
    it is a hidden module in the package ‘elf-0.28’
    Use -v to see a list of the files searched for.

/home/conathan/cfar/reopt.git/deps/elf/src/Data/Elf/TH.hs:4:8:
    Could not find module ‘Data.Elf.Parser’
    it is a hidden module in the package ‘elf-0.28’
    Use -v to see a list of the files searched for.

The modules Data.Elf.Lexer and Data.Elf.Parser are generated from Data/Elf/Lexer.x and Data/Elf/Parser.y. Moving Data.Elf.Lexer and Data.Elf.Parser from extra-modules to exposed-modules in elf.cabal fixes this problem, as the error message indicates it might, but I don't think that's the right solution.

With the exposed-modules hack in place, I then get a probably unrelated error from stack ghci:

/home/conathan/cfar/reopt.git/deps/flexdis86/src/Flexdis86/DefaultParser.hs:25:5:
    Exception when trying to run compile-time code:
      data/optable.xml: openBinaryFile: does not exist (No such file or directory)
    Code: do { let AbsBinds [] []
                     {Exports: [path <= path
                                  <>]
                      Exported types: path :: [Char]
                                      [LclId, Str=DmdType]
                      Binds: ...};
               qAddDependentFile path;
               contents <- ($) qRunIO BS.readFile path;
               .... }
    In the splice:
      $(do { let path = ...;
             qAddDependentFile path;
             contents <- qRunIO $ BS.readFile path;
             .... })

My best guess for a workaround was to mention data/optable.xml in the flexdis86.cabal file:

extra-source-files: data/optable.xml
data-files: data/optable.xml

But that does not help Stack.

In contrast, cabal repl has neither of these problems and starts up without issue.

[mwm]

I think I also have a similar problem - files auto-generated by cabal aren't available from stack ghci or similar. If I do the following:

1. stack new
2. Rename the cabal file to "foobar", changing all occurrences of new-template to foobar in it.
3. add "import Paths_foobar" to app/Main.hs
4. stack exec ghci
5. :load app/Main.hs

This fails to load because "Could not find module 'Paths_foobar'".

Note that "stack ghci" works properly; I just used ghci in the above to illustrate the problem.

[chrisdone]

It now loads like:

chris@retina:~/issue-498$ stack ghci
pkg-a-0.1.0.0: configure
Configuring pkg-a-0.1.0.0...
pkg-a-0.1.0.0: build
Building pkg-a-0.1.0.0...
Preprocessing library pkg-a-0.1.0.0...
[1 of 1] Compiling A                ( .stack-work/dist/x86_64-linux/Cabal-1.22.4.0/build/A.hs, .stack-work/dist/x86_64-linux/Cabal-1.22.4.0/build/A.o )
In-place registering pkg-a-0.1.0.0...
pkg-a-0.1.0.0: install
Installing library in
/home/chris/issue-498/.stack-work/install/x86_64-linux/nightly-2015-06-28/7.10.2/lib/x86_64-linux-ghc-7.10.2/pkg-a-0.1.0.0-KK15ZBdmKl1FvB9hdtPBH4
Registering pkg-a-0.1.0.0...
Configuring GHCi with the following packages: pkg-a
GHCi, version 7.10.2: http://www.haskell.org/ghc/  :? for help
Warning: ignoring unrecognised input `/home/chris/issue-498/A.chs'

I think this needs to launch GHC with A as an argument instead of A.chs, otherwise it doesn't work.

[chrisdone]

Fixed in de397f0, f5a8a7f and 2f725c0.

@mtolly Please confirm.

[ntc2]

For me, the Alex and Happy generated dependencies problem is now gone; thanks! I still have the second problem, but I think it's unrelated:

$ stack ghci
[...]
/home/conathan/cfar/reopt.git/deps/flexdis86/src/Flexdis86/DefaultParser.hs:25:5:
    Exception when trying to run compile-time code:
      data/optable.xml: openBinaryFile: does not exist (No such file or directory)
    Code: do { let AbsBinds [] []
                     {Exports: [path <= path
                                  <>]
                      Exported types: path :: [Char]
                                      [LclId, Str=DmdType]
                      Binds: ...};
               qAddDependentFile path;
               contents <- ($) qRunIO BS.readFile path;
               .... }
    In the splice:
      $(do { let path = ...;
             qAddDependentFile path;
             contents <- qRunIO $ BS.readFile path;
             .... })

Again, stack build still works here.

[mtolly]

It seems I do still have to run stack build before stack ghci in a fresh work directory or whenever a new non-.hs module is added; see the transcript below. But it does seem to be working correctly (in that it compiles and loads the current version, not the version installed in .stack-work).

╭─mtolly@mbp1440  ~/g/stacktest
╰─$ stack --version
Version 0.1.3.0, Git revision 01a628264ff5cac96109d91d9e3cdc3c58b1cac4
╭─mtolly@mbp1440  ~/g/stacktest
╰─$ rm -rf .stack-work/
╭─mtolly@mbp1440  ~/g/stacktest
╰─$ stack ghci
Configuring GHCi with the following packages: pkg-a
GHCi, version 7.10.1: http://www.haskell.org/ghc/  :? for help

<command line>:
    Could not find module ‘A’
    Use -v to see a list of the files searched for.
Failed, modules loaded: none.
Prelude λ
Leaving GHCi.
╭─mtolly@mbp1440  ~/g/stacktest
╰─$ stack build
pkg-a-0.1.0.0: configure
Configuring pkg-a-0.1.0.0...
pkg-a-0.1.0.0: build
Building pkg-a-0.1.0.0...
Preprocessing library pkg-a-0.1.0.0...
[1 of 1] Compiling A                ( .stack-work/dist/x86_64-osx/Cabal-1.22.2.0/build/A.hs, .stack-work/dist/x86_64-osx/Cabal-1.22.2.0/build/A.o )
In-place registering pkg-a-0.1.0.0...
pkg-a-0.1.0.0: install
Installing library in
/Users/mtolly/git/stacktest/.stack-work/install/x86_64-osx/nightly-2015-06-28/7.10.1/lib/x86_64-osx-ghc-7.10.1/pkga_9rCkBC6ycwY3RIqsB0Qe80
Registering pkg-a-0.1.0.0...
╭─mtolly@mbp1440  ~/g/stacktest
╰─$ stack ghci
Configuring GHCi with the following packages: pkg-a
GHCi, version 7.10.1: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling A                ( /Users/mtolly/git/stacktest/.stack-work/dist/x86_64-osx/Cabal-1.22.2.0/build/A.hs, interpreted )
Ok, modules loaded: A.
*A λ