# ghc-imported-from

For a given Haskell source file, determine the path to the Haddock documentation for a symbol at a particular line/col location.

Example: on the file [src/Main.hs](https://github.com/carlohamalainen/ghc-imported-from/blob/master/src/Main.hs),

    ghc-imported-from src/Main.hs Main strOption 18 17

says

    SUCCESS: file:///home/carlo/.stack/snapshots/x86_64-linux/lts-5.8/7.10.3/doc/optparse-applicative-0.12.1.0/Options-Applicative-Builder.html

since the usage of ```strOption``` at line 18, column 17, is from the ```Options.Applicative.Builder``` module.

Difficulties arise in resolving names because some symbols are exported from a certain
package but defined in another, for example ```String``` is defined in
```GHC.Base``` but is exported from the standard prelude, the module
```Prelude```. There are other cases to deal with including qualified
imports, selective imports, imports with hidden components, etc.

## Using with Stack

[Stack](http://docs.haskellstack.org/en/stable/README/) makes everything easier.

Build ghc-imported-from:

    git clone https://github.com/carlohamalainen/ghc-imported-from
    cd ghc-imported-from
    stack build

then add

    `pwd`/.stack-work/install/x86_64-linux/lts-5.8/7.10.3/bin

or similar to your ```$PATH```.

Then in a project that you are working on:

    cd my-project
    stack build
    stack haddock # Must do this!
    ghc-imported-from some/file/Blah.hs Blah f 100 3

### Tests

Run the tests using Stack:

    stack test

### ghcimportedfrom-vim

For Vim users,
follow the instructions at
[https://github.com/carlohamalainen/ghcimportedfrom-vim](https://github.com/carlohamalainen/ghcimportedfrom-vim)
to install the Vim plugin.

### ghc-imported-from-el

For Emacs users, David Christiansen has written [ghc-imported-from-el](https://github.com/david-christiansen/ghc-imported-from-el).

## Usage

See the ```tests``` subdirectory for some examples. Or load your favourite Haskell project and hit F4.

Or watch the screencast (be sure to set 720p HD and then fullscreen):

[https://www.youtube.com/watch?v=7yO_VGCWMu8](https://www.youtube.com/watch?v=7yO_VGCWMu8)

## Notes

```ghc-imported-from``` uses both GHC and ghc-pkg, which
accept arguments in differing formats.  For example GHC takes
```-package-db``` while ghc-pkg takes ```--package-db=```. For more
details: http://www.vex.net/~trebla/haskell/sicp.xhtml

## Debugging

To see the GHC options that have been automatically detected, change into your project's directory and run:

    $ cd ~/ghc-imported-from
    $ cabal repl --with-ghc=fake-ghc-for-ghc-imported-from
    Preprocessing library ghc-imported-from-0.2.0.2...
    --interactive -fbuilding-cabal-package -O0 -outputdir dist/build -odir dist/build -hidir dist/build -stubdir dist/build -i -idist/build -i. -idist/build/autogen -Idist/build/autogen -Idist/build -optP-include -optPdist/build/autogen/cabal_macros.h -package-name ghc-imported-from-0.2.0.2 -hide-all-packages -no-user-package-db -package-db /home/user/ghc-imported-from/.cabal-sandbox/x86_64-linux-ghc-7.6.3-packages.conf.d -package-db dist/package.conf.inplace -package-id Cabal-1.16.0-c6e09e008cd04cf255c1ce0c59aba905 -package-id base-4.6.0.1-8aa5d403c45ea59dcd2c39f123e27d57 -package-id containers-0.5.0.0-ab1dae9a94cd3cc84e7b2805636ebfa2 -package-id directory-1.2.0.1-91a788fd88acd7f149f0f10f5f1e23f2 -package-id filepath-1.3.0.1-b12cbe18566fe1532a1fda4c85e31cbe -package-id ghc-7.6.3-18957ddbb817289f604552aa2da2e879 -package-id ghc-mod-4.1.0-a87501f2667239b3f0bef3e0f3753496 -package-id ghc-paths-0.1.0.9-3817f31ae510ed3b58554933ea527b74 -package-id ghc-syb-utils-0.2.1.2-bf72c1e71339c52f0af404a12449c9d2 -package-id mtl-2.2.0.1-ef91e0abcf7a4fb581ecb7fe83cdcba1 -package-id process-1.1.0.2-76e05340eb66705981411022731ca84a -package-id safe-0.3.4-ba52ca348aecad429ba90450e3aba4c4 -package-id syb-0.4.1-9469ffdd9c6a7ebbf035421c915a08ee -package-id transformers-0.4.1.0-42810d723884ebf2a2dd638e5b22e523 -XHaskell2010 Language.Haskell.GhcImportedFrom Language.Haskell.GhcImportedFrom.UtilsFromGhcMod Language.Haskell.GhcImportedFrom.Types -Wall

## Alternatives

As far as I know the only alternative is the ```fpco/hoogle-doc``` function in
[https://www.fpcomplete.com/page/api](https://www.fpcomplete.com/page/api). Or try Ctrl-i
in the web version of FP Complete.