git-annex/Command/Wanted.hs
Joey Hess 34c8af74ba fix inversion of control in CommandSeek (no behavior changes)
I've been disliking how the command seek actions were written for some
time, with their inversion of control and ugly workarounds.

The last straw to fix it was sync --content, which didn't fit the
Annex [CommandStart] interface well at all. I have not yet made it take
advantage of the changed interface though.

The crucial change, and probably why I didn't do it this way from the
beginning, is to make each CommandStart action be run with exceptions
caught, and if it fails, increment a failure counter in annex state.
So I finally remove the very first code I wrote for git-annex, which
was before I had exception handling in the Annex monad, and so ran outside
that monad, passing state explicitly as it ran each CommandStart action.

This was a real slog from 1 to 5 am.

Test suite passes.

Memory usage is lower than before, sometimes by a couple of megabytes, and
remains constant, even when running in a large repo, and even when
repeatedly failing and incrementing the error counter. So no accidental
laziness space leaks.

Wall clock speed is identical, even in large repos.

This commit was sponsored by an anonymous bitcoiner.
2014-01-20 04:57:36 -04:00

51 lines
1.2 KiB
Haskell

{- git-annex command
-
- Copyright 2013 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Command.Wanted where
import Common.Annex
import qualified Annex
import Command
import qualified Remote
import Logs.PreferredContent
import Types.Messages
import qualified Data.Map as M
def :: [Command]
def = [command "wanted" (paramPair paramRemote (paramOptional paramExpression)) seek
SectionSetup "get or set preferred content expression"]
seek :: CommandSeek
seek = withWords start
start :: [String] -> CommandStart
start = parse
where
parse (name:[]) = go name performGet
parse (name:expr:[]) = go name $ \uuid -> do
showStart "wanted" name
performSet expr uuid
parse _ = error "Specify a repository."
go name a = do
u <- Remote.nameToUUID name
next $ a u
performGet :: UUID -> CommandPerform
performGet uuid = do
Annex.setOutput QuietOutput
m <- preferredContentMapRaw
liftIO $ putStrLn $ fromMaybe "" $ M.lookup uuid m
next $ return True
performSet :: String -> UUID -> CommandPerform
performSet expr uuid = case checkPreferredContentExpression expr of
Just e -> error $ "Parse error: " ++ e
Nothing -> do
preferredContentSet uuid expr
next $ return True