git-annex/doc/devblog/day_297__optparse-applicative.mdwn
2015-07-08 19:40:49 -04:00

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Now working on converting git-annex to use
[optparse-applicative](https://github.com/pcapriotti/optparse-applicative)
for its command line parsing. I've wanted to do this for a long time,
because the current code for options is generally horrible, runs in
IO, and is not at all type safe, while optparse-applicative has wonderful
composable parsers and lets each subcommand have its own data type
repesenting all its options.
What pushed me over the edge is that optparse-applicative has automatic
bash completion!
# source <(git-annex --bash-completion-script `which git-annex`)
# git-annex fsck -
--all --key -S
--from --more -U
Since nobody has managed to write a full bash completion for git-annex
before, let alone keep it up-to-date with changes to the code, automating
the problem away is a really nice win. :)
The conversion is a rather huge undertaking; the diff is already over 3000
lines large after 8 hours of work, and I'm maybe 1/3rd done, with
the groundwork laid (except for global options still todo) and a few
subcommands converted. This won't land for this week's release; it'll
need a lot of testing before it'll be ready for any release.