mercurial/state.py

state: created new class statecheck to handle unfinishedstates

For the purpose of handling states for various multistep operations like
`hg graft`, `hg histedit`, `hg bisect` et al a new class called statecheck
is created .This will help in having a unified approach towards these commands
and handle them with ease.

The class takes in 4 basic arguments which include the name of the command, the
name of the state file associated with it , clearable flag , allowcommit flag.

This also also adds the support of`checkunfinished()` and
`clearunfinished()` to the class.

Tests remain unchanged.

Differential Revision: https://phab.mercurial-scm.org/D6501

# state.py - writing and reading state files in Mercurial
#
# Copyright 2018 Pulkit Goyal <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""
This file contains class to wrap the state for commands and other
related logic.

All the data related to the command state is stored as dictionary in the object.
The class has methods using which the data can be stored to disk in a file under
.hg/ directory.

We store the data on disk in cbor, for which we use the CBOR format to encode
the data.
"""

from __future__ import absolute_import

from .i18n import _

from . import (
    error,
    util,
)
from .utils import (
    cborutil,
)

class cmdstate(object):
    """a wrapper class to store the state of commands like `rebase`, `graft`,
    `histedit`, `shelve` etc. Extensions can also use this to write state files.

    All the data for the state is stored in the form of key-value pairs in a
    dictionary.

    The class object can write all the data to a file in .hg/ directory and
    can populate the object data reading that file.

    Uses cbor to serialize and deserialize data while writing and reading from
    disk.
    """

    def __init__(self, repo, fname):
        """ repo is the repo object
        fname is the file name in which data should be stored in .hg directory
        """
        self._repo = repo
        self.fname = fname

    def read(self):
        """read the existing state file and return a dict of data stored"""
        return self._read()

    def save(self, version, data):
        """write all the state data stored to .hg/<filename> file

        we use third-party library cbor to serialize data to write in the file.
        """
        if not isinstance(version, int):
            raise error.ProgrammingError("version of state file should be"
                                         " an integer")

        with self._repo.vfs(self.fname, 'wb', atomictemp=True) as fp:
            fp.write('%d\n' % version)
            for chunk in cborutil.streamencode(data):
                fp.write(chunk)

    def _read(self):
        """reads the state file and returns a dictionary which contain
        data in the same format as it was before storing"""
        with self._repo.vfs(self.fname, 'rb') as fp:
            try:
                int(fp.readline())
            except ValueError:
                raise error.CorruptedState("unknown version of state file"
                                           " found")

            return cborutil.decodeall(fp.read())[0]

    def delete(self):
        """drop the state file if exists"""
        util.unlinkpath(self._repo.vfs.join(self.fname), ignoremissing=True)

    def exists(self):
        """check whether the state file exists or not"""
        return self._repo.vfs.exists(self.fname)

class _statecheck(object):
    """a utility class that deals with multistep operations like graft,
       histedit, bisect, update etc and check whether such commands
       are in an unfinished conditition or not and return appropriate message
       and hint.
       It also has the ability to register and determine the states of any new
       multistep operation or multistep command extension.
    """

    def __init__(self, opname, fname, clearable=False, allowcommit=False,
                 cmdmsg="", cmdhint=""):
        """opname is the name the command or operation
        fname is the file name in which data should be stored in .hg directory.
        It is None for merge command.
        clearable boolean determines whether or not interrupted states can be
        cleared by running `hg update -C .` which in turn deletes the
        state file.
        allowcommit boolean decides whether commit is allowed during interrupted
        state or not.
        cmdmsg is used to pass a different status message in case standard
        message of the format "abort: cmdname in progress" is not desired.
        cmdhint is used to pass a different hint message in case standard
        message of the format use 'hg cmdname --continue' or
        'hg cmdname --abort'" is not desired.
        """
        self._opname = opname
        self._fname = fname
        self._clearable = clearable
        self._allowcommit = allowcommit
        self._cmdhint = cmdhint
        self._cmdmsg = cmdmsg

    def hint(self):
        """returns the hint message corresponding to the command"""
        if not self._cmdhint:
                return (_("use 'hg %s --continue' or 'hg %s --abort'") %
                        (self._opname, self._opname))
        return self._cmdhint

    def msg(self):
        """returns the status message corresponding to the command"""
        if not self._cmdmsg:
            return _('%s in progress') % (self._opname)
        return self._cmdmsg

    def isunfinished(self, repo):
        """determines whether a multi-step operation is in progress or not"""
        return repo.vfs.exists(self._fname)

# A list of statecheck objects for multistep operations like graft.
_unfinishedstates = []

def addunfinished(opname, **kwargs):
    """this registers a new command or operation to unfinishedstates
    """
    statecheckobj = _statecheck(opname, **kwargs)
    _unfinishedstates.append(statecheckobj)

addunfinished(
    'graft', fname='graftstate', clearable=True,
    cmdhint=_("use 'hg graft --continue' or 'hg graft --stop' to stop")
)
addunfinished(
    'update', fname='updatestate', clearable=True,
    cmdmsg=_('last update was interrupted'),
    cmdhint=_("use 'hg update' to get a consistent checkout")
)