dispatch: factor out command failure handling into a function

Moving the warning generation to a function allows for wrapping and
alternative error handling.

mercurial/dispatch.py

@@ -1,1068 +1,1077 b''
 # dispatch.py - command dispatching for mercurial
 #
 # Copyright 2005-2007 Matt Mackall <[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.
 
 from __future__ import absolute_import, print_function
 
 import atexit
 import difflib
 import errno
 import os
 import pdb
 import re
 import shlex
 import signal
 import socket
 import sys
 import time
 import traceback
 
 
 from .i18n import _
 
 from . import (
     cmdutil,
     commands,
     demandimport,
     encoding,
     error,
     extensions,
     fancyopts,
     fileset,
     hg,
     hook,
     revset,
     templatefilters,
     templatekw,
     templater,
     ui as uimod,
     util,
 )
 
 class request(object):
     def __init__(self, args, ui=None, repo=None, fin=None, fout=None,
                  ferr=None):
         self.args = args
         self.ui = ui
         self.repo = repo
 
         # input/output/error streams
         self.fin = fin
         self.fout = fout
         self.ferr = ferr
 
 def run():
     "run the command in sys.argv"
     sys.exit((dispatch(request(sys.argv[1:])) or 0) & 255)
 
 def _getsimilar(symbols, value):
     sim = lambda x: difflib.SequenceMatcher(None, value, x).ratio()
     # The cutoff for similarity here is pretty arbitrary. It should
     # probably be investigated and tweaked.
     return [s for s in symbols if sim(s) > 0.6]
 
 def _reportsimilar(write, similar):
     if len(similar) == 1:
         write(_("(did you mean %s?)\n") % similar[0])
     elif similar:
         ss = ", ".join(sorted(similar))
         write(_("(did you mean one of %s?)\n") % ss)
 
 def _formatparse(write, inst):
     similar = []
     if isinstance(inst, error.UnknownIdentifier):
         # make sure to check fileset first, as revset can invoke fileset
         similar = _getsimilar(inst.symbols, inst.function)
     if len(inst.args) > 1:
         write(_("hg: parse error at %s: %s\n") %
                          (inst.args[1], inst.args[0]))
         if (inst.args[0][0] == ' '):
             write(_("unexpected leading whitespace\n"))
     else:
         write(_("hg: parse error: %s\n") % inst.args[0])
         _reportsimilar(write, similar)
     if inst.hint:
         write(_("(%s)\n") % inst.hint)
 
 def dispatch(req):
     "run the command specified in req.args"
     if req.ferr:
         ferr = req.ferr
     elif req.ui:
         ferr = req.ui.ferr
     else:
         ferr = sys.stderr
 
     try:
         if not req.ui:
             req.ui = uimod.ui()
         if '--traceback' in req.args:
             req.ui.setconfig('ui', 'traceback', 'on', '--traceback')
 
         # set ui streams from the request
         if req.fin:
             req.ui.fin = req.fin
         if req.fout:
             req.ui.fout = req.fout
         if req.ferr:
             req.ui.ferr = req.ferr
     except error.Abort as inst:
         ferr.write(_("abort: %s\n") % inst)
         if inst.hint:
             ferr.write(_("(%s)\n") % inst.hint)
         return -1
     except error.ParseError as inst:
         _formatparse(ferr.write, inst)
         return -1
 
     msg = ' '.join(' ' in a and repr(a) or a for a in req.args)
     starttime = time.time()
     ret = None
     try:
         ret = _runcatch(req)
     except KeyboardInterrupt:
         try:
             req.ui.warn(_("interrupted!\n"))
         except IOError as inst:
             if inst.errno != errno.EPIPE:
                 raise
         ret = -1
     finally:
         duration = time.time() - starttime
         req.ui.flush()
         req.ui.log("commandfinish", "%s exited %s after %0.2f seconds\n",
                    msg, ret or 0, duration)
     return ret
 
 def _runcatch(req):
     def catchterm(*args):
         raise error.SignalInterrupt
 
     ui = req.ui
     try:
         for name in 'SIGBREAK', 'SIGHUP', 'SIGTERM':
             num = getattr(signal, name, None)
             if num:
                 signal.signal(num, catchterm)
     except ValueError:
         pass # happens if called in a thread
 
     try:
         try:
             debugger = 'pdb'
             debugtrace = {
                 'pdb' : pdb.set_trace
             }
             debugmortem = {
                 'pdb' : pdb.post_mortem
             }
 
             # read --config before doing anything else
             # (e.g. to change trust settings for reading .hg/hgrc)
             cfgs = _parseconfig(req.ui, _earlygetopt(['--config'], req.args))
 
             if req.repo:
                 # copy configs that were passed on the cmdline (--config) to
                 # the repo ui
                 for sec, name, val in cfgs:
                     req.repo.ui.setconfig(sec, name, val, source='--config')
 
             # developer config: ui.debugger
             debugger = ui.config("ui", "debugger")
             debugmod = pdb
             if not debugger or ui.plain():
                 # if we are in HGPLAIN mode, then disable custom debugging
                 debugger = 'pdb'
             elif '--debugger' in req.args:
                 # This import can be slow for fancy debuggers, so only
                 # do it when absolutely necessary, i.e. when actual
                 # debugging has been requested
                 with demandimport.deactivated():
                     try:
                         debugmod = __import__(debugger)
                     except ImportError:
                         pass # Leave debugmod = pdb
 
             debugtrace[debugger] = debugmod.set_trace
             debugmortem[debugger] = debugmod.post_mortem
 
             # enter the debugger before command execution
             if '--debugger' in req.args:
                 ui.warn(_("entering debugger - "
                         "type c to continue starting hg or h for help\n"))
 
                 if (debugger != 'pdb' and
                     debugtrace[debugger] == debugtrace['pdb']):
                     ui.warn(_("%s debugger specified "
                               "but its module was not found\n") % debugger)
                 with demandimport.deactivated():
                     debugtrace[debugger]()
             try:
                 return _dispatch(req)
             finally:
                 ui.flush()
         except: # re-raises
             # enter the debugger when we hit an exception
             if '--debugger' in req.args:
                 traceback.print_exc()
                 debugmortem[debugger](sys.exc_info()[2])
             ui.traceback()
             raise
 
     # Global exception handling, alphabetically
     # Mercurial-specific first, followed by built-in and library exceptions
     except error.AmbiguousCommand as inst:
         ui.warn(_("hg: command '%s' is ambiguous:\n    %s\n") %
                 (inst.args[0], " ".join(inst.args[1])))
     except error.ParseError as inst:
         _formatparse(ui.warn, inst)
         return -1
     except error.LockHeld as inst:
         if inst.errno == errno.ETIMEDOUT:
             reason = _('timed out waiting for lock held by %s') % inst.locker
         else:
             reason = _('lock held by %s') % inst.locker
         ui.warn(_("abort: %s: %s\n") % (inst.desc or inst.filename, reason))
     except error.LockUnavailable as inst:
         ui.warn(_("abort: could not lock %s: %s\n") %
                (inst.desc or inst.filename, inst.strerror))
     except error.CommandError as inst:
         if inst.args[0]:
             ui.warn(_("hg %s: %s\n") % (inst.args[0], inst.args[1]))
             commands.help_(ui, inst.args[0], full=False, command=True)
         else:
             ui.warn(_("hg: %s\n") % inst.args[1])
             commands.help_(ui, 'shortlist')
     except error.OutOfBandError as inst:
         if inst.args:
             msg = _("abort: remote error:\n")
         else:
             msg = _("abort: remote error\n")
         ui.warn(msg)
         if inst.args:
             ui.warn(''.join(inst.args))
         if inst.hint:
             ui.warn('(%s)\n' % inst.hint)
     except error.RepoError as inst:
         ui.warn(_("abort: %s!\n") % inst)
         if inst.hint:
             ui.warn(_("(%s)\n") % inst.hint)
     except error.ResponseError as inst:
         ui.warn(_("abort: %s") % inst.args[0])
         if not isinstance(inst.args[1], basestring):
             ui.warn(" %r\n" % (inst.args[1],))
         elif not inst.args[1]:
             ui.warn(_(" empty string\n"))
         else:
             ui.warn("\n%r\n" % util.ellipsis(inst.args[1]))
     except error.CensoredNodeError as inst:
         ui.warn(_("abort: file censored %s!\n") % inst)
     except error.RevlogError as inst:
         ui.warn(_("abort: %s!\n") % inst)
     except error.SignalInterrupt:
         ui.warn(_("killed!\n"))
     except error.UnknownCommand as inst:
         ui.warn(_("hg: unknown command '%s'\n") % inst.args[0])
         try:
             # check if the command is in a disabled extension
             # (but don't check for extensions themselves)
             commands.help_(ui, inst.args[0], unknowncmd=True)
         except (error.UnknownCommand, error.Abort):
             suggested = False
             if len(inst.args) == 2:
                 sim = _getsimilar(inst.args[1], inst.args[0])
                 if sim:
                     _reportsimilar(ui.warn, sim)
                     suggested = True
             if not suggested:
                 commands.help_(ui, 'shortlist')
     except error.InterventionRequired as inst:
         ui.warn("%s\n" % inst)
         if inst.hint:
             ui.warn(_("(%s)\n") % inst.hint)
         return 1
     except error.Abort as inst:
         ui.warn(_("abort: %s\n") % inst)
         if inst.hint:
             ui.warn(_("(%s)\n") % inst.hint)
     except ImportError as inst:
         ui.warn(_("abort: %s!\n") % inst)
         m = str(inst).split()[-1]
         if m in "mpatch bdiff".split():
             ui.warn(_("(did you forget to compile extensions?)\n"))
         elif m in "zlib".split():
             ui.warn(_("(is your Python install correct?)\n"))
     except IOError as inst:
         if util.safehasattr(inst, "code"):
             ui.warn(_("abort: %s\n") % inst)
         elif util.safehasattr(inst, "reason"):
             try: # usually it is in the form (errno, strerror)
                 reason = inst.reason.args[1]
             except (AttributeError, IndexError):
                 # it might be anything, for example a string
                 reason = inst.reason
             if isinstance(reason, unicode):
                 # SSLError of Python 2.7.9 contains a unicode
                 reason = reason.encode(encoding.encoding, 'replace')
             ui.warn(_("abort: error: %s\n") % reason)
         elif (util.safehasattr(inst, "args")
               and inst.args and inst.args[0] == errno.EPIPE):
             pass
         elif getattr(inst, "strerror", None):
             if getattr(inst, "filename", None):
                 ui.warn(_("abort: %s: %s\n") % (inst.strerror, inst.filename))
             else:
                 ui.warn(_("abort: %s\n") % inst.strerror)
         else:
             raise
     except OSError as inst:
         if getattr(inst, "filename", None) is not None:
             ui.warn(_("abort: %s: '%s'\n") % (inst.strerror, inst.filename))
         else:
             ui.warn(_("abort: %s\n") % inst.strerror)
     except KeyboardInterrupt:
         raise
     except MemoryError:
         ui.warn(_("abort: out of memory\n"))
     except SystemExit as inst:
         # Commands shouldn't sys.exit directly, but give a return code.
         # Just in case catch this and and pass exit code to caller.
         return inst.code
     except socket.error as inst:
         ui.warn(_("abort: %s\n") % inst.args[-1])
-    except: # re-raises
-        # For compatibility checking, we discard the portion of the hg
-        # version after the + on the assumption that if a "normal
-        # user" is running a build with a + in it the packager
-        # probably built from fairly close to a tag and anyone with a
-        # 'make local' copy of hg (where the version number can be out
-        # of date) will be clueful enough to notice the implausible
-        # version number and try updating.
-        ct = util.versiontuple(n=2)
-        worst = None, ct, ''
-        if ui.config('ui', 'supportcontact', None) is None:
-            for name, mod in extensions.extensions():
-                testedwith = getattr(mod, 'testedwith', '')
-                report = getattr(mod, 'buglink', _('the extension author.'))
-                if not testedwith.strip():
-                    # We found an untested extension. It's likely the culprit.
-                    worst = name, 'unknown', report
-                    break
-
-                # Never blame on extensions bundled with Mercurial.
-                if testedwith == 'internal':
-                    continue
-
-                tested = [util.versiontuple(t, 2) for t in testedwith.split()]
-                if ct in tested:
-                    continue
-
-                lower = [t for t in tested if t < ct]
-                nearest = max(lower or tested)
-                if worst[0] is None or nearest < worst[1]:
-                    worst = name, nearest, report
-        if worst[0] is not None:
-            name, testedwith, report = worst
-            if not isinstance(testedwith, str):
-                testedwith = '.'.join([str(c) for c in testedwith])
-            warning = (_('** Unknown exception encountered with '
-                         'possibly-broken third-party extension %s\n'
-                         '** which supports versions %s of Mercurial.\n'
-                         '** Please disable %s and try your action again.\n'
-                         '** If that fixes the bug please report it to %s\n')
-                       % (name, testedwith, name, report))
-        else:
-            bugtracker = ui.config('ui', 'supportcontact', None)
-            if bugtracker is None:
-                bugtracker = _("https://mercurial-scm.org/wiki/BugTracker")
-            warning = (_("** unknown exception encountered, "
-                         "please report by visiting\n** ") + bugtracker + '\n')
-        warning += ((_("** Python %s\n") % sys.version.replace('\n', '')) +
-                    (_("** Mercurial Distributed SCM (version %s)\n") %
-                     util.version()) +
-                    (_("** Extensions loaded: %s\n") %
-                     ", ".join([x[0] for x in extensions.extensions()])))
-        ui.log("commandexception", "%s\n%s\n", warning, traceback.format_exc())
-        ui.warn(warning)
+    except:  # perhaps re-raises
+        if not handlecommandexception(ui):
         raise
 
     return -1
 
 def aliasargs(fn, givenargs):
     args = getattr(fn, 'args', [])
     if args:
         cmd = ' '.join(map(util.shellquote, args))
 
         nums = []
         def replacer(m):
             num = int(m.group(1)) - 1
             nums.append(num)
             if num < len(givenargs):
                 return givenargs[num]
             raise error.Abort(_('too few arguments for command alias'))
         cmd = re.sub(r'\$(\d+|\$)', replacer, cmd)
         givenargs = [x for i, x in enumerate(givenargs)
                      if i not in nums]
         args = shlex.split(cmd)
     return args + givenargs
 
 def aliasinterpolate(name, args, cmd):
     '''interpolate args into cmd for shell aliases
 
     This also handles $0, $@ and "$@".
     '''
     # util.interpolate can't deal with "$@" (with quotes) because it's only
     # built to match prefix + patterns.
     replacemap = dict(('$%d' % (i + 1), arg) for i, arg in enumerate(args))
     replacemap['$0'] = name
     replacemap['$$'] = '$'
     replacemap['$@'] = ' '.join(args)
     # Typical Unix shells interpolate "$@" (with quotes) as all the positional
     # parameters, separated out into words. Emulate the same behavior here by
     # quoting the arguments individually. POSIX shells will then typically
     # tokenize each argument into exactly one word.
     replacemap['"$@"'] = ' '.join(util.shellquote(arg) for arg in args)
     # escape '\$' for regex
     regex = '|'.join(replacemap.keys()).replace('$', r'\$')
     r = re.compile(regex)
     return r.sub(lambda x: replacemap[x.group()], cmd)
 
 class cmdalias(object):
     def __init__(self, name, definition, cmdtable):
         self.name = self.cmd = name
         self.cmdname = ''
         self.definition = definition
         self.fn = None
         self.args = []
         self.opts = []
         self.help = ''
         self.badalias = None
         self.unknowncmd = False
 
         try:
             aliases, entry = cmdutil.findcmd(self.name, cmdtable)
             for alias, e in cmdtable.iteritems():
                 if e is entry:
                     self.cmd = alias
                     break
             self.shadows = True
         except error.UnknownCommand:
             self.shadows = False
 
         if not self.definition:
             self.badalias = _("no definition for alias '%s'") % self.name
             return
 
         if self.definition.startswith('!'):
             self.shell = True
             def fn(ui, *args):
                 env = {'HG_ARGS': ' '.join((self.name,) + args)}
                 def _checkvar(m):
                     if m.groups()[0] == '$':
                         return m.group()
                     elif int(m.groups()[0]) <= len(args):
                         return m.group()
                     else:
                         ui.debug("No argument found for substitution "
                                  "of %i variable in alias '%s' definition."
                                  % (int(m.groups()[0]), self.name))
                         return ''
                 cmd = re.sub(r'\$(\d+|\$)', _checkvar, self.definition[1:])
                 cmd = aliasinterpolate(self.name, args, cmd)
                 return ui.system(cmd, environ=env)
             self.fn = fn
             return
 
         try:
             args = shlex.split(self.definition)
         except ValueError as inst:
             self.badalias = (_("error in definition for alias '%s': %s")
                              % (self.name, inst))
             return
         self.cmdname = cmd = args.pop(0)
         args = map(util.expandpath, args)
 
         for invalidarg in ("--cwd", "-R", "--repository", "--repo", "--config"):
             if _earlygetopt([invalidarg], args):
                 self.badalias = (_("error in definition for alias '%s': %s may "
                                    "only be given on the command line")
                                  % (self.name, invalidarg))
                 return
 
         try:
             tableentry = cmdutil.findcmd(cmd, cmdtable, False)[1]
             if len(tableentry) > 2:
                 self.fn, self.opts, self.help = tableentry
             else:
                 self.fn, self.opts = tableentry
 
             self.args = aliasargs(self.fn, args)
             if self.help.startswith("hg " + cmd):
                 # drop prefix in old-style help lines so hg shows the alias
                 self.help = self.help[4 + len(cmd):]
             self.__doc__ = self.fn.__doc__
 
         except error.UnknownCommand:
             self.badalias = (_("alias '%s' resolves to unknown command '%s'")
                              % (self.name, cmd))
             self.unknowncmd = True
         except error.AmbiguousCommand:
             self.badalias = (_("alias '%s' resolves to ambiguous command '%s'")
                              % (self.name, cmd))
 
     def __getattr__(self, name):
         adefaults = {'norepo': True, 'optionalrepo': False, 'inferrepo': False}
         if name not in adefaults:
             raise AttributeError(name)
         if self.badalias or util.safehasattr(self, 'shell'):
             return adefaults[name]
         return getattr(self.fn, name)
 
     def __call__(self, ui, *args, **opts):
         if self.badalias:
             hint = None
             if self.unknowncmd:
                 try:
                     # check if the command is in a disabled extension
                     cmd, ext = extensions.disabledcmd(ui, self.cmdname)[:2]
                     hint = _("'%s' is provided by '%s' extension") % (cmd, ext)
                 except error.UnknownCommand:
                     pass
             raise error.Abort(self.badalias, hint=hint)
         if self.shadows:
             ui.debug("alias '%s' shadows command '%s'\n" %
                      (self.name, self.cmdname))
 
         if util.safehasattr(self, 'shell'):
             return self.fn(ui, *args, **opts)
         else:
             try:
                 return util.checksignature(self.fn)(ui, *args, **opts)
             except error.SignatureError:
                 args = ' '.join([self.cmdname] + self.args)
                 ui.debug("alias '%s' expands to '%s'\n" % (self.name, args))
                 raise
 
 def addaliases(ui, cmdtable):
     # aliases are processed after extensions have been loaded, so they
     # may use extension commands. Aliases can also use other alias definitions,
     # but only if they have been defined prior to the current definition.
     for alias, definition in ui.configitems('alias'):
         aliasdef = cmdalias(alias, definition, cmdtable)
 
         try:
             olddef = cmdtable[aliasdef.cmd][0]
             if olddef.definition == aliasdef.definition:
                 continue
         except (KeyError, AttributeError):
             # definition might not exist or it might not be a cmdalias
             pass
 
         cmdtable[aliasdef.name] = (aliasdef, aliasdef.opts, aliasdef.help)
 
 def _parse(ui, args):
     options = {}
     cmdoptions = {}
 
     try:
         args = fancyopts.fancyopts(args, commands.globalopts, options)
     except fancyopts.getopt.GetoptError as inst:
         raise error.CommandError(None, inst)
 
     if args:
         cmd, args = args[0], args[1:]
         aliases, entry = cmdutil.findcmd(cmd, commands.table,
                                          ui.configbool("ui", "strict"))
         cmd = aliases[0]
         args = aliasargs(entry[0], args)
         defaults = ui.config("defaults", cmd)
         if defaults:
             args = map(util.expandpath, shlex.split(defaults)) + args
         c = list(entry[1])
     else:
         cmd = None
         c = []
 
     # combine global options into local
     for o in commands.globalopts:
         c.append((o[0], o[1], options[o[1]], o[3]))
 
     try:
         args = fancyopts.fancyopts(args, c, cmdoptions, True)
     except fancyopts.getopt.GetoptError as inst:
         raise error.CommandError(cmd, inst)
 
     # separate global options back out
     for o in commands.globalopts:
         n = o[1]
         options[n] = cmdoptions[n]
         del cmdoptions[n]
 
     return (cmd, cmd and entry[0] or None, args, options, cmdoptions)
 
 def _parseconfig(ui, config):
     """parse the --config options from the command line"""
     configs = []
 
     for cfg in config:
         try:
             name, value = [cfgelem.strip()
                            for cfgelem in cfg.split('=', 1)]
             section, name = name.split('.', 1)
             if not section or not name:
                 raise IndexError
             ui.setconfig(section, name, value, '--config')
             configs.append((section, name, value))
         except (IndexError, ValueError):
             raise error.Abort(_('malformed --config option: %r '
                                '(use --config section.name=value)') % cfg)
 
     return configs
 
 def _earlygetopt(aliases, args):
     """Return list of values for an option (or aliases).
 
     The values are listed in the order they appear in args.
     The options and values are removed from args.
 
     >>> args = ['x', '--cwd', 'foo', 'y']
     >>> _earlygetopt(['--cwd'], args), args
     (['foo'], ['x', 'y'])
 
     >>> args = ['x', '--cwd=bar', 'y']
     >>> _earlygetopt(['--cwd'], args), args
     (['bar'], ['x', 'y'])
 
     >>> args = ['x', '-R', 'foo', 'y']
     >>> _earlygetopt(['-R'], args), args
     (['foo'], ['x', 'y'])
 
     >>> args = ['x', '-Rbar', 'y']
     >>> _earlygetopt(['-R'], args), args
     (['bar'], ['x', 'y'])
     """
     try:
         argcount = args.index("--")
     except ValueError:
         argcount = len(args)
     shortopts = [opt for opt in aliases if len(opt) == 2]
     values = []
     pos = 0
     while pos < argcount:
         fullarg = arg = args[pos]
         equals = arg.find('=')
         if equals > -1:
             arg = arg[:equals]
         if arg in aliases:
             del args[pos]
             if equals > -1:
                 values.append(fullarg[equals + 1:])
                 argcount -= 1
             else:
                 if pos + 1 >= argcount:
                     # ignore and let getopt report an error if there is no value
                     break
                 values.append(args.pop(pos))
                 argcount -= 2
         elif arg[:2] in shortopts:
             # short option can have no following space, e.g. hg log -Rfoo
             values.append(args.pop(pos)[2:])
             argcount -= 1
         else:
             pos += 1
     return values
 
 def runcommand(lui, repo, cmd, fullargs, ui, options, d, cmdpats, cmdoptions):
     # run pre-hook, and abort if it fails
     hook.hook(lui, repo, "pre-%s" % cmd, True, args=" ".join(fullargs),
               pats=cmdpats, opts=cmdoptions)
     ret = _runcommand(ui, options, cmd, d)
     # run post-hook, passing command result
     hook.hook(lui, repo, "post-%s" % cmd, False, args=" ".join(fullargs),
               result=ret, pats=cmdpats, opts=cmdoptions)
     return ret
 
 def _getlocal(ui, rpath, wd=None):
     """Return (path, local ui object) for the given target path.
 
     Takes paths in [cwd]/.hg/hgrc into account."
     """
     if wd is None:
         try:
             wd = os.getcwd()
         except OSError as e:
             raise error.Abort(_("error getting current working directory: %s") %
                               e.strerror)
     path = cmdutil.findrepo(wd) or ""
     if not path:
         lui = ui
     else:
         lui = ui.copy()
         lui.readconfig(os.path.join(path, ".hg", "hgrc"), path)
 
     if rpath and rpath[-1]:
         path = lui.expandpath(rpath[-1])
         lui = ui.copy()
         lui.readconfig(os.path.join(path, ".hg", "hgrc"), path)
 
     return path, lui
 
 def _checkshellalias(lui, ui, args, precheck=True):
     """Return the function to run the shell alias, if it is required
 
     'precheck' is whether this function is invoked before adding
     aliases or not.
     """
     options = {}
 
     try:
         args = fancyopts.fancyopts(args, commands.globalopts, options)
     except fancyopts.getopt.GetoptError:
         return
 
     if not args:
         return
 
     if precheck:
         strict = True
         cmdtable = commands.table.copy()
         addaliases(lui, cmdtable)
     else:
         strict = False
         cmdtable = commands.table
 
     cmd = args[0]
     try:
         aliases, entry = cmdutil.findcmd(cmd, cmdtable, strict)
     except (error.AmbiguousCommand, error.UnknownCommand):
         return
 
     cmd = aliases[0]
     fn = entry[0]
 
     if cmd and util.safehasattr(fn, 'shell'):
         d = lambda: fn(ui, *args[1:])
         return lambda: runcommand(lui, None, cmd, args[:1], ui, options, d,
                                   [], {})
 
 def _cmdattr(ui, cmd, func, attr):
     try:
         return getattr(func, attr)
     except AttributeError:
         ui.deprecwarn("missing attribute '%s', use @command decorator "
                       "to register '%s'" % (attr, cmd), '3.8')
         return False
 
 _loaded = set()
 
 # list of (objname, loadermod, loadername) tuple:
 # - objname is the name of an object in extension module, from which
 #   extra information is loaded
 # - loadermod is the module where loader is placed
 # - loadername is the name of the function, which takes (ui, extensionname,
 #   extraobj) arguments
 extraloaders = [
     ('cmdtable', commands, 'loadcmdtable'),
     ('filesetpredicate', fileset, 'loadpredicate'),
     ('revsetpredicate', revset, 'loadpredicate'),
     ('templatefilter', templatefilters, 'loadfilter'),
     ('templatefunc', templater, 'loadfunction'),
     ('templatekeyword', templatekw, 'loadkeyword'),
 ]
 
 def _dispatch(req):
     args = req.args
     ui = req.ui
 
     # check for cwd
     cwd = _earlygetopt(['--cwd'], args)
     if cwd:
         os.chdir(cwd[-1])
 
     rpath = _earlygetopt(["-R", "--repository", "--repo"], args)
     path, lui = _getlocal(ui, rpath)
 
     # Now that we're operating in the right directory/repository with
     # the right config settings, check for shell aliases
     shellaliasfn = _checkshellalias(lui, ui, args)
     if shellaliasfn:
         return shellaliasfn()
 
     # Configure extensions in phases: uisetup, extsetup, cmdtable, and
     # reposetup. Programs like TortoiseHg will call _dispatch several
     # times so we keep track of configured extensions in _loaded.
     extensions.loadall(lui)
     exts = [ext for ext in extensions.extensions() if ext[0] not in _loaded]
     # Propagate any changes to lui.__class__ by extensions
     ui.__class__ = lui.__class__
 
     # (uisetup and extsetup are handled in extensions.loadall)
 
     for name, module in exts:
         for objname, loadermod, loadername in extraloaders:
             extraobj = getattr(module, objname, None)
             if extraobj is not None:
                 getattr(loadermod, loadername)(ui, name, extraobj)
         _loaded.add(name)
 
     # (reposetup is handled in hg.repository)
 
     addaliases(lui, commands.table)
 
     if not lui.configbool("ui", "strict"):
         # All aliases and commands are completely defined, now.
         # Check abbreviation/ambiguity of shell alias again, because shell
         # alias may cause failure of "_parse" (see issue4355)
         shellaliasfn = _checkshellalias(lui, ui, args, precheck=False)
         if shellaliasfn:
             return shellaliasfn()
 
     # check for fallback encoding
     fallback = lui.config('ui', 'fallbackencoding')
     if fallback:
         encoding.fallbackencoding = fallback
 
     fullargs = args
     cmd, func, args, options, cmdoptions = _parse(lui, args)
 
     if options["config"]:
         raise error.Abort(_("option --config may not be abbreviated!"))
     if options["cwd"]:
         raise error.Abort(_("option --cwd may not be abbreviated!"))
     if options["repository"]:
         raise error.Abort(_(
             "option -R has to be separated from other options (e.g. not -qR) "
             "and --repository may only be abbreviated as --repo!"))
 
     if options["encoding"]:
         encoding.encoding = options["encoding"]
     if options["encodingmode"]:
         encoding.encodingmode = options["encodingmode"]
     if options["time"]:
         def get_times():
             t = os.times()
             if t[4] == 0.0: # Windows leaves this as zero, so use time.clock()
                 t = (t[0], t[1], t[2], t[3], time.clock())
             return t
         s = get_times()
         def print_time():
             t = get_times()
             ui.warn(_("time: real %.3f secs (user %.3f+%.3f sys %.3f+%.3f)\n") %
                 (t[4]-s[4], t[0]-s[0], t[2]-s[2], t[1]-s[1], t[3]-s[3]))
         atexit.register(print_time)
 
     uis = set([ui, lui])
 
     if req.repo:
         uis.add(req.repo.ui)
 
     if options['verbose'] or options['debug'] or options['quiet']:
         for opt in ('verbose', 'debug', 'quiet'):
             val = str(bool(options[opt]))
             for ui_ in uis:
                 ui_.setconfig('ui', opt, val, '--' + opt)
 
     if options['traceback']:
         for ui_ in uis:
             ui_.setconfig('ui', 'traceback', 'on', '--traceback')
 
     if options['noninteractive']:
         for ui_ in uis:
             ui_.setconfig('ui', 'interactive', 'off', '-y')
 
     if cmdoptions.get('insecure', False):
         for ui_ in uis:
             ui_.setconfig('web', 'cacerts', '!', '--insecure')
 
     if options['version']:
         return commands.version_(ui)
     if options['help']:
         return commands.help_(ui, cmd, command=cmd is not None)
     elif not cmd:
         return commands.help_(ui, 'shortlist')
 
     repo = None
     cmdpats = args[:]
     if not _cmdattr(ui, cmd, func, 'norepo'):
         # use the repo from the request only if we don't have -R
         if not rpath and not cwd:
             repo = req.repo
 
         if repo:
             # set the descriptors of the repo ui to those of ui
             repo.ui.fin = ui.fin
             repo.ui.fout = ui.fout
             repo.ui.ferr = ui.ferr
         else:
             try:
                 repo = hg.repository(ui, path=path)
                 if not repo.local():
                     raise error.Abort(_("repository '%s' is not local") % path)
                 repo.ui.setconfig("bundle", "mainreporoot", repo.root, 'repo')
             except error.RequirementError:
                 raise
             except error.RepoError:
                 if rpath and rpath[-1]: # invalid -R path
                     raise
                 if not _cmdattr(ui, cmd, func, 'optionalrepo'):
                     if (_cmdattr(ui, cmd, func, 'inferrepo') and
                         args and not path):
                         # try to infer -R from command args
                         repos = map(cmdutil.findrepo, args)
                         guess = repos[0]
                         if guess and repos.count(guess) == len(repos):
                             req.args = ['--repository', guess] + fullargs
                             return _dispatch(req)
                     if not path:
                         raise error.RepoError(_("no repository found in '%s'"
                                                 " (.hg not found)")
                                               % os.getcwd())
                     raise
         if repo:
             ui = repo.ui
             if options['hidden']:
                 repo = repo.unfiltered()
         args.insert(0, repo)
     elif rpath:
         ui.warn(_("warning: --repository ignored\n"))
 
     msg = ' '.join(' ' in a and repr(a) or a for a in fullargs)
     ui.log("command", '%s\n', msg)
     d = lambda: util.checksignature(func)(ui, *args, **cmdoptions)
     try:
         return runcommand(lui, repo, cmd, fullargs, ui, options, d,
                           cmdpats, cmdoptions)
     finally:
         if repo and repo != req.repo:
             repo.close()
 
 def lsprofile(ui, func, fp):
     format = ui.config('profiling', 'format', default='text')
     field = ui.config('profiling', 'sort', default='inlinetime')
     limit = ui.configint('profiling', 'limit', default=30)
     climit = ui.configint('profiling', 'nested', default=0)
 
     if format not in ['text', 'kcachegrind']:
         ui.warn(_("unrecognized profiling format '%s'"
                     " - Ignored\n") % format)
         format = 'text'
 
     try:
         from . import lsprof
     except ImportError:
         raise error.Abort(_(
             'lsprof not available - install from '
             'http://codespeak.net/svn/user/arigo/hack/misc/lsprof/'))
     p = lsprof.Profiler()
     p.enable(subcalls=True)
     try:
         return func()
     finally:
         p.disable()
 
         if format == 'kcachegrind':
             from . import lsprofcalltree
             calltree = lsprofcalltree.KCacheGrind(p)
             calltree.output(fp)
         else:
             # format == 'text'
             stats = lsprof.Stats(p.getstats())
             stats.sort(field)
             stats.pprint(limit=limit, file=fp, climit=climit)
 
 def flameprofile(ui, func, fp):
     try:
         from flamegraph import flamegraph
     except ImportError:
         raise error.Abort(_(
             'flamegraph not available - install from '
             'https://github.com/evanhempel/python-flamegraph'))
     # developer config: profiling.freq
     freq = ui.configint('profiling', 'freq', default=1000)
     filter_ = None
     collapse_recursion = True
     thread = flamegraph.ProfileThread(fp, 1.0 / freq,
                                       filter_, collapse_recursion)
     start_time = time.clock()
     try:
         thread.start()
         func()
     finally:
         thread.stop()
         thread.join()
         print('Collected %d stack frames (%d unique) in %2.2f seconds.' % (
             time.clock() - start_time, thread.num_frames(),
             thread.num_frames(unique=True)))
 
 
 def statprofile(ui, func, fp):
     try:
         import statprof
     except ImportError:
         raise error.Abort(_(
             'statprof not available - install using "easy_install statprof"'))
 
     freq = ui.configint('profiling', 'freq', default=1000)
     if freq > 0:
         statprof.reset(freq)
     else:
         ui.warn(_("invalid sampling frequency '%s' - ignoring\n") % freq)
 
     statprof.start()
     try:
         return func()
     finally:
         statprof.stop()
         statprof.display(fp)
 
 def _runcommand(ui, options, cmd, cmdfunc):
     """Enables the profiler if applicable.
 
     ``profiling.enabled`` - boolean config that enables or disables profiling
     """
     def checkargs():
         try:
             return cmdfunc()
         except error.SignatureError:
             raise error.CommandError(cmd, _("invalid arguments"))
 
     if options['profile'] or ui.configbool('profiling', 'enabled'):
         profiler = os.getenv('HGPROF')
         if profiler is None:
             profiler = ui.config('profiling', 'type', default='ls')
         if profiler not in ('ls', 'stat', 'flame'):
             ui.warn(_("unrecognized profiler '%s' - ignored\n") % profiler)
             profiler = 'ls'
 
         output = ui.config('profiling', 'output')
 
         if output == 'blackbox':
             import StringIO
             fp = StringIO.StringIO()
         elif output:
             path = ui.expandpath(output)
             fp = open(path, 'wb')
         else:
             fp = sys.stderr
 
         try:
             if profiler == 'ls':
                 return lsprofile(ui, checkargs, fp)
             elif profiler == 'flame':
                 return flameprofile(ui, checkargs, fp)
             else:
                 return statprofile(ui, checkargs, fp)
         finally:
             if output:
                 if output == 'blackbox':
                     val = "Profile:\n%s" % fp.getvalue()
                     # ui.log treats the input as a format string,
                     # so we need to escape any % signs.
                     val = val.replace('%', '%%')
                     ui.log('profile', val)
                 fp.close()
     else:
         return checkargs()
+
+def handlecommandexception(ui):
+    """Produce a warning message for broken commands
+
+    Called when handling an exception; the exception is reraised if
+    this function returns False, ignored otherwise.
+    """
+    # For compatibility checking, we discard the portion of the hg
+    # version after the + on the assumption that if a "normal
+    # user" is running a build with a + in it the packager
+    # probably built from fairly close to a tag and anyone with a
+    # 'make local' copy of hg (where the version number can be out
+    # of date) will be clueful enough to notice the implausible
+    # version number and try updating.
+    ct = util.versiontuple(n=2)
+    worst = None, ct, ''
+    if ui.config('ui', 'supportcontact', None) is None:
+        for name, mod in extensions.extensions():
+            testedwith = getattr(mod, 'testedwith', '')
+            report = getattr(mod, 'buglink', _('the extension author.'))
+            if not testedwith.strip():
+                # We found an untested extension. It's likely the culprit.
+                worst = name, 'unknown', report
+                break
+
+            # Never blame on extensions bundled with Mercurial.
+            if testedwith == 'internal':
+                continue
+
+            tested = [util.versiontuple(t, 2) for t in testedwith.split()]
+            if ct in tested:
+                continue
+
+            lower = [t for t in tested if t < ct]
+            nearest = max(lower or tested)
+            if worst[0] is None or nearest < worst[1]:
+                worst = name, nearest, report
+    if worst[0] is not None:
+        name, testedwith, report = worst
+        if not isinstance(testedwith, str):
+            testedwith = '.'.join([str(c) for c in testedwith])
+        warning = (_('** Unknown exception encountered with '
+                     'possibly-broken third-party extension %s\n'
+                     '** which supports versions %s of Mercurial.\n'
+                     '** Please disable %s and try your action again.\n'
+                     '** If that fixes the bug please report it to %s\n')
+                   % (name, testedwith, name, report))
+    else:
+        bugtracker = ui.config('ui', 'supportcontact', None)
+        if bugtracker is None:
+            bugtracker = _("https://mercurial-scm.org/wiki/BugTracker")
+        warning = (_("** unknown exception encountered, "
+                     "please report by visiting\n** ") + bugtracker + '\n')
+    warning += ((_("** Python %s\n") % sys.version.replace('\n', '')) +
+                (_("** Mercurial Distributed SCM (version %s)\n") %
+                 util.version()) +
+                (_("** Extensions loaded: %s\n") %
+                 ", ".join([x[0] for x in extensions.extensions()])))
+    ui.log("commandexception", "%s\n%s\n", warning, traceback.format_exc())
+    ui.warn(warning)
+    return False  # re-raise the exception