cabal-cargs
cabal-cargs is a command line program for extracting compiler relevant arguments from a cabal file and print them out formatted so that they're directly usable as arguments for ghc or hdevtools.
The main motivation for writing cabal-cargs was to get a mostly just working default, non modified hdevtools.
If you want to call hdevtools check for a source file of a cabalized project and would like to consider all compiler relevant arguments in the cabal file - like hs-source-dirs, ghc-options, cpp-options ... - and also the cabal sandbox, then you could just use cabal-cargs the following way:
$> hdevtools check `cabal-cargs --format=hdevtools --sourcefile=Source.hs` Source.hs
This call of cabal-cargs will search for a cabal file starting at the directory of Source.hs upwards the directory tree. The cabal file is then searched for a fitting section for the given source file. A section is considered fitting if the source file is contained in a directory or sub-directory listed in hs-source-dirs.
At the end the fields of the found sections are printed out in the desired format.
Normally you don't want to use cabal-cargs manually, but use it to initialize the options of hdevtools. So in the case of the editor vim and the plugin vim-hdevtools you could use something like:
function! s:CabalCargs(args) let l:output = system('cabal-cargs ' . a:args) if v:shell_error != 0 let l:lines = split(l:output, '\n') echohl ErrorMsg echomsg 'args: ' . a:args for l:line in l:lines echomsg l:line endfor echohl None return '' endif return l:output endfunction function! s:HdevtoolsOptions() return s:CabalCargs('--format=hdevtools --sourcefile=' . shellescape(expand('%'))) endfunction autocmd Bufenter *.hs :call s:InitHaskellVars() function! s:InitHaskellVars() if filereadable(expand('%')) let g:hdevtools_options = s:HdevtoolsOptions() endif endfunction
To see if cabal-cargs did the right thing you can verify the hdevtools options by calling in the vim command line:
:let g:hdevtools_options
Example: Compiler Arguments from Cabal File
Instead of searching for the cabal file by a source file the cabal file can be given explicitly:
$> cabal-cargs --cabalfile=Some.cabal
If an additional source file is given, then the cabal file is searched for a fitting section.
If no cabal file nor a source file is given, then starting at the current directory a cabal file is searched upwards the directory tree.
Sections
If you don't want any automatic finding of sections or only want to consider a certain section, then you could do this by using the options:
--library --executable=name --testsuite=name --benchmark=name --allsections
You can use multiple of these options at once and even specify multiple e.g. executables at once: --executable=exe1 --executable=exe2 ....
Fields
By default all fields of a section are printed out. You can constrain the output by the options: --only=name or --ignore=name. These options can be specified multiple times.
The allowed names are the field names from the cabal file, just the hyphen replaced by an underscore e.g.: hs-source-dirs -> hs_source_dirs.
Currently supported cabal fields are:
hs_source_dirs ghc_options default_extensions default_language cpp_options c_sources cc_options extra_lib_dirs extra_libraries ld_options include_dirs includes build_depends
There are further some special fields:
package_db root_dir autogen_hs_source_dirs autogen_include_dirs autogen_includes hdevtools_socket
It's not quite true, that all fields are printed out if not constrained, that's only the case for the pure formatting option. For the other formatting options currently the fields c_sources and ld_options are ignored and additionally the ghc formatting option ignores the hdevtools_socket field.
Flags
The conditional parts of the cabal file are respected by cabal-cargs by taking the default values of the flags defined in the cabal file into account.
You can overwrite the default values of the flags with the options:
--enable=FLAGNAME --disable=FLAGNAME
It's also possible to overwrite the OS and Arch values - which by default are the ones the cabal library was build on - with the options:
--os=OSNAME --arch=ARCHNAME
By default the fields are formatted for the ghc compiler. The available options for --format are:
pure prints the values like they are present in the cabal file and is mostly only useful in conjunction with --only to get the value of one cabal field.
Installation
It's recommended to build cabal-cargs in a cabal sandbox with: cabal install cabal-cargs.
