git-annex/Types/Command.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

79 lines
2.8 KiB
Haskell

{- git-annex command data types
-
- Copyright 2010-2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Types.Command where
import Data.Ord
import Types
{- A command runs in these stages.
-
- a. The check stage runs checks, that error out if
- anything prevents the command from running. -}
data CommandCheck = CommandCheck { idCheck :: Int, runCheck :: Annex () }
{- b. The seek stage takes the parameters passed to the command,
- looks through the repo to find the ones that are relevant
- to that command (ie, new files to add), and runs commandAction
- to handle all necessary actions. -}
type CommandSeek = [String] -> Annex ()
{- c. The start stage is run before anything is printed about the
- command, is passed some input, and can early abort it
- if the input does not make sense. It should run quickly and
- should not modify Annex state. -}
type CommandStart = Annex (Maybe CommandPerform)
{- d. The perform stage is run after a message is printed about the command
- being run, and it should be where the bulk of the work happens. -}
type CommandPerform = Annex (Maybe CommandCleanup)
{- e. The cleanup stage is run only if the perform stage succeeds, and it
- returns the overall success/fail of the command. -}
type CommandCleanup = Annex Bool
{- A command is defined by specifying these things. -}
data Command = Command
{ cmdoptions :: [Option] -- command-specific options
, cmdnorepo :: Maybe (CmdParams -> IO ()) -- an action to run when not in a repo
, cmdcheck :: [CommandCheck] -- check stage
, cmdnocommit :: Bool -- don't commit journalled state changes
, cmdnomessages :: Bool -- don't output normal messages
, cmdname :: String
, cmdparamdesc :: String -- description of params for usage
, cmdseek :: CommandSeek
, cmdsection :: CommandSection
, cmddesc :: String -- description of command for usage
}
type CmdParams = [String]
{- CommandCheck functions can be compared using their unique id. -}
instance Eq CommandCheck where
a == b = idCheck a == idCheck b
instance Eq Command where
a == b = cmdname a == cmdname b
{- Order commands by name. -}
instance Ord Command where
compare = comparing cmdname
{- The same sections are listed in doc/git-annex.mdwn -}
data CommandSection
= SectionCommon
| SectionSetup
| SectionMaintenance
| SectionQuery
| SectionUtility
| SectionPlumbing
deriving (Eq, Ord, Enum, Bounded)
descSection :: CommandSection -> String
descSection SectionCommon = "Commonly used commands"
descSection SectionSetup = "Repository setup commands"
descSection SectionMaintenance = "Repository maintenance commands"
descSection SectionQuery = "Query commands"
descSection SectionUtility = "Utility commands"
descSection SectionPlumbing = "Plumbing commands"