Mercurial > hg
view mercurial/lock.py @ 48981:f3aafd785e65
filemerge: add support for partial conflict resolution by external tool
A common class of merge conflicts is in imports/#includes/etc. It's
relatively easy to write a tool that can resolve these conflicts,
perhaps by naively just unioning the statements and leaving any
cleanup to other tools to do later [1]. Such specialized tools cannot
generally resolve all conflicts in a file, of course. Let's therefore
call them "partial merge tools". Note that the internal simplemerge
algorithm is such a partial merge tool - one that only resolves
trivial "conflicts" where one side is unchanged or both sides change
in the same way.
One can also imagine having smarter language-aware partial tools that
merge the AST. It may be useful for such tools to interactively let
the user resolve any conflicts it can't resolve itself. However,
having the option of implementing it as a partial merge tool means
that the developer doesn't *need* to create a UI for it. Instead, the
user can resolve any remaining conflicts with their regular merge tool
(e.g. `:merge3` or `meld).
We don't currently have a way to let the user define such partial
merge tools. That's what this patch addresses. It lets the user
configure partial merge tools to run. Each tool can be configured to
run only on files matching certain patterns (e.g. "*.py"). The tool
takes three inputs (local, base, other) and resolves conflicts by
updating these in place. For example, let's say the inputs are these:
base:
```
import sys
def main():
print('Hello')
```
local:
```
import os
import sys
def main():
print('Hi')
```
other:
```
import re
import sys
def main():
print('Howdy')
```
A partial merge tool could now resolve the conflicting imports by
replacing the import statements in *all* files by the following
snippet, while leaving the remainder of the files unchanged.
```
import os
import re
import sys
```
As a result, simplemerge and any regular merge tool that runs after
the partial merge tool(s) will consider the imports to be
non-conflicting and will only present the conflict in `main()` to the
user.
Differential Revision: https://phab.mercurial-scm.org/D12356
author | Martin von Zweigbergk <martinvonz@google.com> |
---|---|
date | Tue, 18 Jan 2022 13:05:21 -0800 |
parents | 642e31cb55f0 |
children | 2e726c934fcd |
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# lock.py - simple advisory locking scheme for mercurial # # Copyright 2005, 2006 Olivia Mackall <olivia@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. import contextlib import errno import os import signal import socket import time import warnings from .i18n import _ from .pycompat import getattr from . import ( encoding, error, pycompat, util, ) from .utils import procutil def _getlockprefix(): """Return a string which is used to differentiate pid namespaces It's useful to detect "dead" processes and remove stale locks with confidence. Typically it's just hostname. On modern linux, we include an extra Linux-specific pid namespace identifier. """ result = encoding.strtolocal(socket.gethostname()) if pycompat.sysplatform.startswith(b'linux'): try: result += b'/%x' % os.stat(b'/proc/self/ns/pid').st_ino except OSError as ex: if ex.errno not in (errno.ENOENT, errno.EACCES, errno.ENOTDIR): raise return result @contextlib.contextmanager def _delayedinterrupt(): """Block signal interrupt while doing something critical This makes sure that the code block wrapped by this context manager won't be interrupted. For Windows developers: It appears not possible to guard time.sleep() from CTRL_C_EVENT, so please don't use time.sleep() to test if this is working. """ assertedsigs = [] blocked = False orighandlers = {} def raiseinterrupt(num): if num == getattr(signal, 'SIGINT', None) or num == getattr( signal, 'CTRL_C_EVENT', None ): raise KeyboardInterrupt else: raise error.SignalInterrupt def catchterm(num, frame): if blocked: assertedsigs.append(num) else: raiseinterrupt(num) try: # save handlers first so they can be restored even if a setup is # interrupted between signal.signal() and orighandlers[] =. for name in [ b'CTRL_C_EVENT', b'SIGINT', b'SIGBREAK', b'SIGHUP', b'SIGTERM', ]: num = getattr(signal, name, None) if num and num not in orighandlers: orighandlers[num] = signal.getsignal(num) try: for num in orighandlers: signal.signal(num, catchterm) except ValueError: pass # in a thread? no luck blocked = True yield finally: # no simple way to reliably restore all signal handlers because # any loops, recursive function calls, except blocks, etc. can be # interrupted. so instead, make catchterm() raise interrupt. blocked = False try: for num, handler in orighandlers.items(): signal.signal(num, handler) except ValueError: pass # in a thread? # re-raise interrupt exception if any, which may be shadowed by a new # interrupt occurred while re-raising the first one if assertedsigs: raiseinterrupt(assertedsigs[0]) def trylock(ui, vfs, lockname, timeout, warntimeout, *args, **kwargs): """return an acquired lock or raise an a LockHeld exception This function is responsible to issue warnings and or debug messages about the held lock while trying to acquires it.""" def printwarning(printer, locker): """issue the usual "waiting on lock" message through any channel""" # show more details for new-style locks if b':' in locker: host, pid = locker.split(b":", 1) msg = _( b"waiting for lock on %s held by process %r on host %r\n" ) % ( pycompat.bytestr(l.desc), pycompat.bytestr(pid), pycompat.bytestr(host), ) else: msg = _(b"waiting for lock on %s held by %r\n") % ( l.desc, pycompat.bytestr(locker), ) printer(msg) l = lock(vfs, lockname, 0, *args, dolock=False, **kwargs) debugidx = 0 if (warntimeout and timeout) else -1 warningidx = 0 if not timeout: warningidx = -1 elif warntimeout: warningidx = warntimeout delay = 0 while True: try: l._trylock() break except error.LockHeld as inst: if delay == debugidx: printwarning(ui.debug, inst.locker) if delay == warningidx: printwarning(ui.warn, inst.locker) if timeout <= delay: raise error.LockHeld( errno.ETIMEDOUT, inst.filename, l.desc, inst.locker ) time.sleep(1) delay += 1 l.delay = delay if l.delay: if 0 <= warningidx <= l.delay: ui.warn(_(b"got lock after %d seconds\n") % l.delay) else: ui.debug(b"got lock after %d seconds\n" % l.delay) if l.acquirefn: l.acquirefn() return l class lock: """An advisory lock held by one process to control access to a set of files. Non-cooperating processes or incorrectly written scripts can ignore Mercurial's locking scheme and stomp all over the repository, so don't do that. Typically used via localrepository.lock() to lock the repository store (.hg/store/) or localrepository.wlock() to lock everything else under .hg/.""" # lock is symlink on platforms that support it, file on others. # symlink is used because create of directory entry and contents # are atomic even over nfs. # old-style lock: symlink to pid # new-style lock: symlink to hostname:pid _host = None def __init__( self, vfs, fname, timeout=-1, releasefn=None, acquirefn=None, desc=None, signalsafe=True, dolock=True, ): self.vfs = vfs self.f = fname self.held = 0 self.timeout = timeout self.releasefn = releasefn self.acquirefn = acquirefn self.desc = desc if signalsafe: self._maybedelayedinterrupt = _delayedinterrupt else: self._maybedelayedinterrupt = util.nullcontextmanager self.postrelease = [] self.pid = self._getpid() if dolock: self.delay = self.lock() if self.acquirefn: self.acquirefn() def __enter__(self): return self def __exit__(self, exc_type, exc_value, exc_tb): success = all(a is None for a in (exc_type, exc_value, exc_tb)) self.release(success=success) def __del__(self): if self.held: warnings.warn( "use lock.release instead of del lock", category=DeprecationWarning, stacklevel=2, ) # ensure the lock will be removed # even if recursive locking did occur self.held = 1 self.release() def _getpid(self): # wrapper around procutil.getpid() to make testing easier return procutil.getpid() def lock(self): timeout = self.timeout while True: try: self._trylock() return self.timeout - timeout except error.LockHeld as inst: if timeout != 0: time.sleep(1) if timeout > 0: timeout -= 1 continue raise error.LockHeld( errno.ETIMEDOUT, inst.filename, self.desc, inst.locker ) def _trylock(self): if self.held: self.held += 1 return if lock._host is None: lock._host = _getlockprefix() lockname = b'%s:%d' % (lock._host, self.pid) retry = 5 while not self.held and retry: retry -= 1 try: with self._maybedelayedinterrupt(): self.vfs.makelock(lockname, self.f) self.held = 1 except (OSError, IOError) as why: if why.errno == errno.EEXIST: locker = self._readlock() if locker is None: continue locker = self._testlock(locker) if locker is not None: raise error.LockHeld( errno.EAGAIN, self.vfs.join(self.f), self.desc, locker, ) else: raise error.LockUnavailable( why.errno, why.strerror, why.filename, self.desc ) if not self.held: # use empty locker to mean "busy for frequent lock/unlock # by many processes" raise error.LockHeld( errno.EAGAIN, self.vfs.join(self.f), self.desc, b"" ) def _readlock(self): """read lock and return its value Returns None if no lock exists, pid for old-style locks, and host:pid for new-style locks. """ try: return self.vfs.readlock(self.f) except (OSError, IOError) as why: if why.errno == errno.ENOENT: return None raise def _lockshouldbebroken(self, locker): if locker is None: return False try: host, pid = locker.split(b":", 1) except ValueError: return False if host != lock._host: return False try: pid = int(pid) except ValueError: return False if procutil.testpid(pid): return False return True def _testlock(self, locker): if not self._lockshouldbebroken(locker): return locker # if locker dead, break lock. must do this with another lock # held, or can race and break valid lock. try: with lock(self.vfs, self.f + b'.break', timeout=0): locker = self._readlock() if not self._lockshouldbebroken(locker): return locker self.vfs.unlink(self.f) except error.LockError: return locker def testlock(self): """return id of locker if lock is valid, else None. If old-style lock, we cannot tell what machine locker is on. with new-style lock, if locker is on this machine, we can see if locker is alive. If locker is on this machine but not alive, we can safely break lock. The lock file is only deleted when None is returned. """ locker = self._readlock() return self._testlock(locker) def release(self, success=True): """release the lock and execute callback function if any If the lock has been acquired multiple times, the actual release is delayed to the last release call.""" if self.held > 1: self.held -= 1 elif self.held == 1: self.held = 0 if self._getpid() != self.pid: # we forked, and are not the parent return try: if self.releasefn: self.releasefn() finally: try: self.vfs.unlink(self.f) except OSError: pass # The postrelease functions typically assume the lock is not held # at all. for callback in self.postrelease: callback(success) # Prevent double usage and help clear cycles. self.postrelease = None def release(*locks): for lock in locks: if lock is not None: lock.release()