Can't display -ddump-splices result.

[waddlaw]

$ stack build --ghc-options='-ddump-splices'

I want to display on the standard output, not to save to a file.

Question

Why does the extraBuildOptions function specify the " -ddump-hi -ddump-to-file" option by default?

extraBuildOptions wc bopts = do
    colorOpt <- appropriateGhcColorFlag
    let ddumpOpts = " -ddump-hi -ddump-to-file"
        optsFlag = compilerOptionsCabalFlag wc
        baseOpts = ddumpOpts ++ maybe "" (" " ++) colorOpt
    if toCoverage (boptsTestOpts bopts)
      then do
        hpcIndexDir <- toFilePathNoTrailingSep <$> hpcRelativeDir
        return [optsFlag, "-hpcdir " ++ hpcIndexDir ++ baseOpts]
      else
        return [optsFlag, baseOpts]

If remove this option, I think it will work as expected.

Stack version

$ stack --version
Version 1.10.0, Git revision 3b61926935c28efd10c8e6870f927a7d8eb5523c (dirty) (6119 commits) x86_64 hpack-0.29.6

[mattaudesse]

Thanks @waddlaw - that seems like a really good question and I'm not sure what the answer should be!

I think @borsboom might be the best person to ask since that setting seems to have been added in 6e65345.

[snoyberg]

It's necessary to grab information available in the HI dump files, like addDependentFile information. The alternative would require an extra executable of the ghc executable for each .hi file, which is prohibitively expensive. I agree that the current situation is far from ideal, but it's AFAIK the best trade-off we have.

[waddlaw]

Thanks @snoyberg

What about providing stack build --ddump-dir option. For example, following command run listed the outputed dump files.

$ find $(stack path --dist-dir) -name "*.dump-*"
.stack-work/dist/x86_64-linux/Cabal-2.2.0.1/build/src/Test.dump-simpl
.stack-work/dist/x86_64-linux/Cabal-2.2.0.1/build/src/Ins.dump-stg
.stack-work/dist/x86_64-linux/Cabal-2.2.0.1/build/src/Lib.dump-stg
.stack-work/dist/x86_64-linux/Cabal-2.2.0.1/build/src/Ins.dump-simpl
.stack-work/dist/x86_64-linux/Cabal-2.2.0.1/build/src/Lib.dump-simpl
.stack-work/dist/x86_64-linux/Cabal-2.2.0.1/build/src/Test.dump-stg
.stack-work/dist/x86_64-linux/Cabal-2.2.0.1/build/src/Lib.dump-splices
.stack-work/dist/x86_64-linux/Cabal-2.2.0.1/build/.stack-work/dist/x86_64-linux/Cabal-2.2.0.1/build/autogen/Paths_th_example.dump-stg
.stack-work/dist/x86_64-linux/Cabal-2.2.0.1/build/.stack-work/dist/x86_64-linux/Cabal-2.2.0.1/build/autogen/Paths_th_example.dump-simpl

if these file move to the specified dump-dir, I think better than now (Easy to understand the output location.). Perhaps not strictly correct the above result, but very useful for me. What do you think about this?

[snoyberg]

I'd be OK with such a PR. It may be simpler to copy the files from where they're currently output by GHC to a new location, instead of trying to convince GHC to use a new directory and then parse it. Are you interested in taking a stab at a PR?