[Haskell-cafe] How to determine the right path to haddock html documentation?

[Carlo Hamalainen]

Hi,

I'm writing a patch for ghcmod-vim so that a user can look up the
haddock html documentation for a symbol. My code makes three system
calls, e.g. to look up "Just" it does:

    $ ghc-mod info foo.hs Foo Just
    data Maybe a = ... | Just a     -- Defined in `Data.Maybe'

    $ ghc-pkg find-module Data.Maybe --simple-output
    haskell2010-1.1.1.0 base-4.6.0.1

    $ ghc-pkg field base-4.6.0.1 haddock-html
    haddock-html:
/home/carlo/opt/ghc-7.6.3_build/share/doc/ghc/html/libraries/base-4.6.0.1

Then "Data.Maybe" is changed to Data-Maybe.html" and appended to the
haddock-html value. But this procedure doesn't work in general, for
example when looking up String:

    $ ghc-mod info foo.hs Foo String
    type String = [Char]     -- Defined in `GHC.Base'

    $ ghc-pkg find-module GHC.Base
    /home/carlo/opt/ghc-7.6.3_build/lib/ghc-7.6.3/package.conf.d
       base-4.6.0.1
    /home/carlo/.ghc/x86_64-linux-7.6.3/package.conf.d

    $ ghc-pkg field base-4.6.0.1 haddock-html
    haddock-html:
/home/carlo/opt/ghc-7.6.3_build/share/doc/ghc/html/libraries/base-4.6.0.1

    $ ls
/home/carlo/opt/ghc-7.6.3_build/share/doc/ghc/html/libraries/base-4.6.0.1/GHC-Base.html
    ls: cannot access
/home/carlo/opt/ghc-7.6.3_build/share/doc/ghc/html/libraries/base-4.6.0.1/GHC-Base.html:
No such file or directory

because the html is in the src subdirectory:

    $ ls
/home/carlo/opt/ghc-7.6.3_build/share/doc/ghc/html/libraries/base-4.6.0.1/src/GHC-Base.html
   
/home/carlo/opt/ghc-7.6.3_build/share/doc/ghc/html/libraries/base-4.6.0.1/src/GHC-Base.html

But this isn't even the right place to go, one should look at the
Prelude file

http://hackage.haskell.org/package/base-4.6.0.1/docs/Prelude.html#t:String

which is what Hoogle suggests. How does Hoogle get it right?

It looks like haskell-mode for emacs runs into a similar problem:

https://github.com/haskell/haskell-mode/blob/master/inf-haskell.el#L734-L740

-------------------------------
  (defvar inferior-haskell-ghc-internal-ident-alist
    ;; FIXME: Fill this table, ideally semi-automatically.
    '(("GHC.Base.return" . "Control.Monad.return")
      ("GHC.List" . "Data.List")))

  (defun inferior-haskell-map-internal-ghc-ident (ident)
    "Try to translate some internal GHC identifier to its alter ego in
haskell docs."
-------------------------------

Thanks,

-- 
Carlo Hamalainen
http://carlo-hamalainen.net

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/haskell-cafe/attachments/20131213/89f96d3f/attachment.html>