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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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error.py
329 lines | 10.4 KiB | text/x-python | PythonLexer
# error.py - Mercurial exceptions
#
# Copyright 2005-2008 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""Mercurial exceptions.
This allows us to catch exceptions at higher levels without forcing
imports.
"""
from __future__ import absolute_import
# Do not import anything but pycompat here, please
from . import pycompat
def _tobytes(exc):
"""Byte-stringify exception in the same way as BaseException_str()"""
if not exc.args:
return b''
if len(exc.args) == 1:
return pycompat.bytestr(exc.args[0])
return b'(%s)' % b', '.join(b"'%s'" % pycompat.bytestr(a) for a in exc.args)
class Hint(object):
"""Mix-in to provide a hint of an error
This should come first in the inheritance list to consume a hint and
pass remaining arguments to the exception class.
"""
def __init__(self, *args, **kw):
self.hint = kw.pop(r'hint', None)
super(Hint, self).__init__(*args, **kw)
class RevlogError(Hint, Exception):
__bytes__ = _tobytes
class FilteredIndexError(IndexError):
__bytes__ = _tobytes
class LookupError(RevlogError, KeyError):
def __init__(self, name, index, message):
self.name = name
self.index = index
# this can't be called 'message' because at least some installs of
# Python 2.6+ complain about the 'message' property being deprecated
self.lookupmessage = message
if isinstance(name, bytes) and len(name) == 20:
from .node import short
name = short(name)
RevlogError.__init__(self, '%s@%s: %s' % (index, name, message))
def __bytes__(self):
return RevlogError.__bytes__(self)
def __str__(self):
return RevlogError.__str__(self)
class AmbiguousPrefixLookupError(LookupError):
pass
class FilteredLookupError(LookupError):
pass
class ManifestLookupError(LookupError):
pass
class CommandError(Exception):
"""Exception raised on errors in parsing the command line."""
__bytes__ = _tobytes
class InterventionRequired(Hint, Exception):
"""Exception raised when a command requires human intervention."""
__bytes__ = _tobytes
class Abort(Hint, Exception):
"""Raised if a command needs to print an error and exit."""
__bytes__ = _tobytes
class HookLoadError(Abort):
"""raised when loading a hook fails, aborting an operation
Exists to allow more specialized catching."""
class HookAbort(Abort):
"""raised when a validation hook fails, aborting an operation
Exists to allow more specialized catching."""
class ConfigError(Abort):
"""Exception raised when parsing config files"""
class UpdateAbort(Abort):
"""Raised when an update is aborted for destination issue"""
class MergeDestAbort(Abort):
"""Raised when an update is aborted for destination issues"""
class NoMergeDestAbort(MergeDestAbort):
"""Raised when an update is aborted because there is nothing to merge"""
class ManyMergeDestAbort(MergeDestAbort):
"""Raised when an update is aborted because destination is ambiguous"""
class ResponseExpected(Abort):
"""Raised when an EOF is received for a prompt"""
def __init__(self):
from .i18n import _
Abort.__init__(self, _('response expected'))
class OutOfBandError(Hint, Exception):
"""Exception raised when a remote repo reports failure"""
__bytes__ = _tobytes
class ParseError(Hint, Exception):
"""Raised when parsing config files and {rev,file}sets (msg[, pos])"""
__bytes__ = _tobytes
class PatchError(Exception):
__bytes__ = _tobytes
class UnknownIdentifier(ParseError):
"""Exception raised when a {rev,file}set references an unknown identifier"""
def __init__(self, function, symbols):
from .i18n import _
ParseError.__init__(self, _("unknown identifier: %s") % function)
self.function = function
self.symbols = symbols
class RepoError(Hint, Exception):
__bytes__ = _tobytes
class RepoLookupError(RepoError):
pass
class FilteredRepoLookupError(RepoLookupError):
pass
class CapabilityError(RepoError):
pass
class RequirementError(RepoError):
"""Exception raised if .hg/requires has an unknown entry."""
class StdioError(IOError):
"""Raised if I/O to stdout or stderr fails"""
def __init__(self, err):
IOError.__init__(self, err.errno, err.strerror)
# no __bytes__() because error message is derived from the standard IOError
class UnsupportedMergeRecords(Abort):
def __init__(self, recordtypes):
from .i18n import _
self.recordtypes = sorted(recordtypes)
s = ' '.join(self.recordtypes)
Abort.__init__(
self, _('unsupported merge state records: %s') % s,
hint=_('see https://mercurial-scm.org/wiki/MergeStateRecords for '
'more information'))
class UnknownVersion(Abort):
"""generic exception for aborting from an encounter with an unknown version
"""
def __init__(self, msg, hint=None, version=None):
self.version = version
super(UnknownVersion, self).__init__(msg, hint=hint)
class LockError(IOError):
def __init__(self, errno, strerror, filename, desc):
IOError.__init__(self, errno, strerror, filename)
self.desc = desc
# no __bytes__() because error message is derived from the standard IOError
class LockHeld(LockError):
def __init__(self, errno, filename, desc, locker):
LockError.__init__(self, errno, 'Lock held', filename, desc)
self.locker = locker
class LockUnavailable(LockError):
pass
# LockError is for errors while acquiring the lock -- this is unrelated
class LockInheritanceContractViolation(RuntimeError):
__bytes__ = _tobytes
class ResponseError(Exception):
"""Raised to print an error with part of output and exit."""
__bytes__ = _tobytes
class UnknownCommand(Exception):
"""Exception raised if command is not in the command table."""
__bytes__ = _tobytes
class AmbiguousCommand(Exception):
"""Exception raised if command shortcut matches more than one command."""
__bytes__ = _tobytes
# derived from KeyboardInterrupt to simplify some breakout code
class SignalInterrupt(KeyboardInterrupt):
"""Exception raised on SIGTERM and SIGHUP."""
class SignatureError(Exception):
__bytes__ = _tobytes
class PushRaced(RuntimeError):
"""An exception raised during unbundling that indicate a push race"""
__bytes__ = _tobytes
class ProgrammingError(Hint, RuntimeError):
"""Raised if a mercurial (core or extension) developer made a mistake"""
def __init__(self, msg, *args, **kwargs):
# On Python 3, turn the message back into a string since this is
# an internal-only error that won't be printed except in a
# stack traces.
msg = pycompat.sysstr(msg)
super(ProgrammingError, self).__init__(msg, *args, **kwargs)
__bytes__ = _tobytes
class WdirUnsupported(Exception):
"""An exception which is raised when 'wdir()' is not supported"""
__bytes__ = _tobytes
# bundle2 related errors
class BundleValueError(ValueError):
"""error raised when bundle2 cannot be processed"""
__bytes__ = _tobytes
class BundleUnknownFeatureError(BundleValueError):
def __init__(self, parttype=None, params=(), values=()):
self.parttype = parttype
self.params = params
self.values = values
if self.parttype is None:
msg = 'Stream Parameter'
else:
msg = parttype
entries = self.params
if self.params and self.values:
assert len(self.params) == len(self.values)
entries = []
for idx, par in enumerate(self.params):
val = self.values[idx]
if val is None:
entries.append(val)
else:
entries.append("%s=%r" % (par, pycompat.maybebytestr(val)))
if entries:
msg = '%s - %s' % (msg, ', '.join(entries))
ValueError.__init__(self, msg)
class ReadOnlyPartError(RuntimeError):
"""error raised when code tries to alter a part being generated"""
__bytes__ = _tobytes
class PushkeyFailed(Abort):
"""error raised when a pushkey part failed to update a value"""
def __init__(self, partid, namespace=None, key=None, new=None, old=None,
ret=None):
self.partid = partid
self.namespace = namespace
self.key = key
self.new = new
self.old = old
self.ret = ret
# no i18n expected to be processed into a better message
Abort.__init__(self, 'failed to update value for "%s/%s"'
% (namespace, key))
class CensoredNodeError(RevlogError):
"""error raised when content verification fails on a censored node
Also contains the tombstone data substituted for the uncensored data.
"""
def __init__(self, filename, node, tombstone):
from .node import short
RevlogError.__init__(self, '%s:%s' % (filename, short(node)))
self.tombstone = tombstone
class CensoredBaseError(RevlogError):
"""error raised when a delta is rejected because its base is censored
A delta based on a censored revision must be formed as single patch
operation which replaces the entire base with new content. This ensures
the delta may be applied by clones which have not censored the base.
"""
class InvalidBundleSpecification(Exception):
"""error raised when a bundle specification is invalid.
This is used for syntax errors as opposed to support errors.
"""
__bytes__ = _tobytes
class UnsupportedBundleSpecification(Exception):
"""error raised when a bundle specification is not supported."""
__bytes__ = _tobytes
class CorruptedState(Exception):
"""error raised when a command is not able to read its state from file"""
__bytes__ = _tobytes
class PeerTransportError(Abort):
"""Transport-level I/O error when communicating with a peer repo."""
class InMemoryMergeConflictsError(Exception):
"""Exception raised when merge conflicts arose during an in-memory merge."""
__bytes__ = _tobytes
class WireprotoCommandError(Exception):
"""Represents an error during execution of a wire protocol command.
Should only be thrown by wire protocol version 2 commands.
The error is a formatter string and an optional iterable of arguments.
"""
def __init__(self, message, args=None):
self.message = message
self.messageargs = args