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localrepo: iteratively derive local repository type...
localrepo: iteratively derive local repository type This commit implements the dynamic local repository type derivation that was explained in the recent commit bfeab472e3c0 "localrepo: create new function for instantiating a local repo object." Instead of a static localrepository class/type which must be customized after construction, we now dynamically construct a type by building up base classes/types to represent specific repository interfaces. Conceptually, the end state is similar to what was happening when various extensions would monkeypatch the __class__ of newly-constructed repo instances. However, the approach is inverted. Instead of making the instance then customizing it, we do the customization up front by influencing the behavior of the type then we instantiate that custom type. This approach gives us much more flexibility. For example, we can use completely separate classes for implementing different aspects of the repository. For example, we could have one class representing revlog-based file storage and another representing non-revlog based file storage. When then choose which implementation to use based on the presence of repo requirements. A concern with this approach is that it creates a lot more types and complexity and that complexity adds overhead. Yes, it is true that this approach will result in more types being created. Yes, this is more complicated than traditional "instantiate a static type." However, I believe the alternatives to supporting alternate storage backends are just as complicated. (Before I arrived at this solution, I had patches storing factory functions on local repo instances for e.g. constructing a file storage instance. We ended up having a handful of these. And this was logically identical to assigning custom methods. Since we were logically changing the type of the instance, I figured it would be better to just use specialized types instead of introducing levels of abstraction at run-time.) On the performance front, I don't believe that having N base classes has any significant performance overhead compared to just a single base class. Intuition says that Python will need to iterate the base classes to find an attribute. However, CPython caches method lookups: as long as the __class__ or MRO isn't changing, method attribute lookup should be constant time after first access. And non-method attributes are stored in __dict__, of which there is only 1 per object, so the number of base classes for __dict__ is irrelevant. Anyway, this commit splits up the monolithic completelocalrepository interface into sub-interfaces: 1 for file storage and 1 representing everything else. We've taught ``makelocalrepository()`` to call a series of factory functions which will produce types implementing specific interfaces. It then calls type() to create a new type from the built-up list of base types. This commit should be considered a start and not the end state. I suspect we'll hit a number of problems as we start to implement alternate storage backends: * Passing custom arguments to __init__ and setting custom attributes on __dict__. * Customizing the set of interfaces that are needed. e.g. the "readonly" intent could translate to not requesting an interface providing methods related to writing. * More ergonomic way for extensions to insert themselves so their callbacks aren't unconditionally called. * Wanting to modify vfs instances, other arguments passed to __init__. That being said, this code is usable in its current state and I'm convinced future commits will demonstrate the value in this approach. Differential Revision: https://phab.mercurial-scm.org/D4642

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transport.py
132 lines | 4.9 KiB | text/x-python | PythonLexer
# -*- coding: utf-8 -*-
# Copyright (C) 2007 Daniel Holth <dholth@fastmail.fm>
# This is a stripped-down version of the original bzr-svn transport.py,
# Copyright (C) 2006 Jelmer Vernooij <jelmer@samba.org>
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program; if not, see <http://www.gnu.org/licenses/>.
from __future__ import absolute_import
import svn.client
import svn.core
import svn.ra
Pool = svn.core.Pool
SubversionException = svn.core.SubversionException
from mercurial import (
util,
)
# Some older versions of the Python bindings need to be
# explicitly initialized. But what we want to do probably
# won't work worth a darn against those libraries anyway!
svn.ra.initialize()
svn_config = None
def _create_auth_baton(pool):
"""Create a Subversion authentication baton. """
import svn.client
# Give the client context baton a suite of authentication
# providers.h
providers = [
svn.client.get_simple_provider(pool),
svn.client.get_username_provider(pool),
svn.client.get_ssl_client_cert_file_provider(pool),
svn.client.get_ssl_client_cert_pw_file_provider(pool),
svn.client.get_ssl_server_trust_file_provider(pool),
]
# Platform-dependent authentication methods
getprovider = getattr(svn.core, 'svn_auth_get_platform_specific_provider',
None)
if getprovider:
# Available in svn >= 1.6
for name in ('gnome_keyring', 'keychain', 'kwallet', 'windows'):
for type in ('simple', 'ssl_client_cert_pw', 'ssl_server_trust'):
p = getprovider(name, type, pool)
if p:
providers.append(p)
else:
if util.safehasattr(svn.client, 'get_windows_simple_provider'):
providers.append(svn.client.get_windows_simple_provider(pool))
return svn.core.svn_auth_open(providers, pool)
class NotBranchError(SubversionException):
pass
class SvnRaTransport(object):
"""
Open an ra connection to a Subversion repository.
"""
def __init__(self, url="", ra=None):
self.pool = Pool()
self.svn_url = url
self.username = ''
self.password = ''
# Only Subversion 1.4 has reparent()
if ra is None or not util.safehasattr(svn.ra, 'reparent'):
self.client = svn.client.create_context(self.pool)
ab = _create_auth_baton(self.pool)
self.client.auth_baton = ab
global svn_config
if svn_config is None:
svn_config = svn.core.svn_config_get_config(None)
self.client.config = svn_config
try:
self.ra = svn.client.open_ra_session(
self.svn_url,
self.client, self.pool)
except SubversionException as xxx_todo_changeme:
(inst, num) = xxx_todo_changeme.args
if num in (svn.core.SVN_ERR_RA_ILLEGAL_URL,
svn.core.SVN_ERR_RA_LOCAL_REPOS_OPEN_FAILED,
svn.core.SVN_ERR_BAD_URL):
raise NotBranchError(url)
raise
else:
self.ra = ra
svn.ra.reparent(self.ra, self.svn_url.encode('utf8'))
class Reporter(object):
def __init__(self, reporter_data):
self._reporter, self._baton = reporter_data
def set_path(self, path, revnum, start_empty, lock_token, pool=None):
svn.ra.reporter2_invoke_set_path(self._reporter, self._baton,
path, revnum, start_empty, lock_token, pool)
def delete_path(self, path, pool=None):
svn.ra.reporter2_invoke_delete_path(self._reporter, self._baton,
path, pool)
def link_path(self, path, url, revision, start_empty, lock_token,
pool=None):
svn.ra.reporter2_invoke_link_path(self._reporter, self._baton,
path, url, revision, start_empty, lock_token,
pool)
def finish_report(self, pool=None):
svn.ra.reporter2_invoke_finish_report(self._reporter,
self._baton, pool)
def abort_report(self, pool=None):
svn.ra.reporter2_invoke_abort_report(self._reporter,
self._baton, pool)
def do_update(self, revnum, path, *args, **kwargs):
return self.Reporter(svn.ra.do_update(self.ra, revnum, path,
*args, **kwargs))