Completion for GHCi commands in inferior-haskell buffers

Purpose

To support completion for GHCi commands (like :load, :module, :set etc.) in inferior-haskell buffers.

Installation

To turn on GHCi commands completion in inferior-haskell buffers, add this to .emacs:

(add-hook 'inferior-haskell-mode-hook 'turn-on-ghci-completion)

Otherwise, call turn-on-ghci-completion.

You may also want to set ghci-completion-ghc-pkg-additional-args to the list of additional argument to supply to ghc-pkg. For example, this variable can be used to specify which database (user or global) or which package config file to use.

Limitations:

• This package is developed for Emacs 24 and it probably only works with Emacs 24. In particular, we rely on lexical bindings, which have been introduced in Emacs 24, and on pcomplete, which is effectively broken in 23.2.

• Only the following commands are supported: :add, :browse[!], :cd, :edit, :load, :module, :set, :unset, :show. It would be nice to have shell completion for :!, for example.

• The starred versions of the commands :add, :browse[!], :load, and :module are not supported, partly because I don't use them, and partly because, for example, :module offers completion only on the exposed modules in registered packages in both the global and user databases, and for these :module *<mod> is meaningless.

• :set and :unset support only a subset of all GHC flags: language extensions, warnings, and debugging options. Adding completion for other flags is trivial. It would be nice, however, to be able to generate the list of all GHC flags programmatically.