dispatch: ignore failure to flush ui

When the pager dies, we get a `SIGPIPE`. That causes
`error.SignalInterrupt` to be raised ` (from `ui._catchterm()`). Any
further writes or flushes will cause further `SIGPIPE`s and furhter
`error.SignalInterrupt`. If we write or flush outside of the
try/except that handle `KeyboardInterrupt` (which
`error.SignalInterrupt` is a subclass of), then control will escape
from the `dispatch` module. Let's fix that by ignoring errors from
flushing the ui.

I would have rather fixed this by restoring the stdout and stderr
streams when the pager dies, but it gets complicated because of
multiple ui instances (ui/lui) and different pager setups between
regular hg and chg.

This changes a test in `test-pager.t`, but I don't understand why. I
would have thought that all the output from the command should have
gone to the broken pager.

Differential Revision: https://phab.mercurial-scm.org/D11627

mercurial/dispatch.py

@@ -1,1390 +1,1404 b''
 # dispatch.py - command dispatching for mercurial
 #
 # Copyright 2005-2007 Olivia 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 errno
 import getopt
 import io
 import os
 import pdb
 import re
 import signal
 import sys
 import traceback
 
 
 from .i18n import _
 from .pycompat import getattr
 
 from hgdemandimport import tracing
 
 from . import (
     cmdutil,
     color,
     commands,
     demandimport,
     encoding,
     error,
     extensions,
     fancyopts,
     help,
     hg,
     hook,
     localrepo,
     profiling,
     pycompat,
     rcutil,
     registrar,
     requirements as requirementsmod,
     scmutil,
     ui as uimod,
     util,
     vfs,
 )
 
 from .utils import (
     procutil,
     stringutil,
     urlutil,
 )
 
 
 class request(object):
     def __init__(
         self,
         args,
         ui=None,
         repo=None,
         fin=None,
         fout=None,
         ferr=None,
         fmsg=None,
         prereposetups=None,
     ):
         self.args = args
         self.ui = ui
         self.repo = repo
 
         # input/output/error streams
         self.fin = fin
         self.fout = fout
         self.ferr = ferr
         # separate stream for status/error messages
         self.fmsg = fmsg
 
         # remember options pre-parsed by _earlyparseopts()
         self.earlyoptions = {}
 
         # reposetups which run before extensions, useful for chg to pre-fill
         # low-level repo state (for example, changelog) before extensions.
         self.prereposetups = prereposetups or []
 
         # store the parsed and canonical command
         self.canonical_command = None
 
     def _runexithandlers(self):
         exc = None
         handlers = self.ui._exithandlers
         try:
             while handlers:
                 func, args, kwargs = handlers.pop()
                 try:
                     func(*args, **kwargs)
                 except:  # re-raises below
                     if exc is None:
                         exc = sys.exc_info()[1]
                     self.ui.warnnoi18n(b'error in exit handlers:\n')
                     self.ui.traceback(force=True)
         finally:
             if exc is not None:
                 raise exc
 
 
 def _flushstdio(ui, err):
     status = None
     # In all cases we try to flush stdio streams.
     if util.safehasattr(ui, b'fout'):
         assert ui is not None  # help pytype
         assert ui.fout is not None  # help pytype
         try:
             ui.fout.flush()
         except IOError as e:
             err = e
             status = -1
 
     if util.safehasattr(ui, b'ferr'):
         assert ui is not None  # help pytype
         assert ui.ferr is not None  # help pytype
         try:
             if err is not None and err.errno != errno.EPIPE:
                 ui.ferr.write(
                     b'abort: %s\n' % encoding.strtolocal(err.strerror)
                 )
             ui.ferr.flush()
         # There's not much we can do about an I/O error here. So (possibly)
         # change the status code and move on.
         except IOError:
             status = -1
 
     return status
 
 
 def run():
     """run the command in sys.argv"""
     try:
         initstdio()
         with tracing.log('parse args into request'):
             req = request(pycompat.sysargv[1:])
 
         status = dispatch(req)
         _silencestdio()
     except KeyboardInterrupt:
         # Catch early/late KeyboardInterrupt as last ditch. Here nothing will
         # be printed to console to avoid another IOError/KeyboardInterrupt.
         status = -1
     sys.exit(status & 255)
 
 
 if pycompat.ispy3:
 
     def initstdio():
         # stdio streams on Python 3 are io.TextIOWrapper instances proxying another
         # buffer. These streams will normalize \n to \r\n by default. Mercurial's
         # preferred mechanism for writing output (ui.write()) uses io.BufferedWriter
         # instances, which write to the underlying stdio file descriptor in binary
         # mode. ui.write() uses \n for line endings and no line ending normalization
         # is attempted through this interface. This "just works," even if the system
         # preferred line ending is not \n.
         #
         # But some parts of Mercurial (e.g. hooks) can still send data to sys.stdout
         # and sys.stderr. They will inherit the line ending normalization settings,
         # potentially causing e.g. \r\n to be emitted. Since emitting \n should
         # "just work," here we change the sys.* streams to disable line ending
         # normalization, ensuring compatibility with our ui type.
 
         if sys.stdout is not None:
             # write_through is new in Python 3.7.
             kwargs = {
                 "newline": "\n",
                 "line_buffering": sys.stdout.line_buffering,
             }
             if util.safehasattr(sys.stdout, "write_through"):
                 # pytype: disable=attribute-error
                 kwargs["write_through"] = sys.stdout.write_through
                 # pytype: enable=attribute-error
             sys.stdout = io.TextIOWrapper(
                 sys.stdout.buffer,
                 sys.stdout.encoding,
                 sys.stdout.errors,
                 **kwargs
             )
 
         if sys.stderr is not None:
             kwargs = {
                 "newline": "\n",
                 "line_buffering": sys.stderr.line_buffering,
             }
             if util.safehasattr(sys.stderr, "write_through"):
                 # pytype: disable=attribute-error
                 kwargs["write_through"] = sys.stderr.write_through
                 # pytype: enable=attribute-error
             sys.stderr = io.TextIOWrapper(
                 sys.stderr.buffer,
                 sys.stderr.encoding,
                 sys.stderr.errors,
                 **kwargs
             )
 
         if sys.stdin is not None:
             # No write_through on read-only stream.
             sys.stdin = io.TextIOWrapper(
                 sys.stdin.buffer,
                 sys.stdin.encoding,
                 sys.stdin.errors,
                 # None is universal newlines mode.
                 newline=None,
                 line_buffering=sys.stdin.line_buffering,
             )
 
     def _silencestdio():
         for fp in (sys.stdout, sys.stderr):
             if fp is None:
                 continue
             # Check if the file is okay
             try:
                 fp.flush()
                 continue
             except IOError:
                 pass
             # Otherwise mark it as closed to silence "Exception ignored in"
             # message emitted by the interpreter finalizer.
             try:
                 fp.close()
             except IOError:
                 pass
 
 
 else:
 
     def initstdio():
         for fp in (sys.stdin, sys.stdout, sys.stderr):
             procutil.setbinary(fp)
 
     def _silencestdio():
         pass
 
 
 def _formatargs(args):
     return b' '.join(procutil.shellquote(a) for a in args)
 
 
 def dispatch(req):
     """run the command specified in req.args; returns an integer status code"""
     err = None
     try:
         status = _rundispatch(req)
     except error.StdioError as e:
         err = e
         status = -1
 
-    ret = _flushstdio(req.ui, err)
-    if ret and not status:
-        status = ret
+    # Somehow we have to catcht he exception here; catching it inside
+    # _flushstdio() doesn't work.
+    try:
+        ret = _flushstdio(req.ui, err)
+        if ret and not status:
+            status = ret
+    except BaseException:
+        pass
     return status
 
 
 def _rundispatch(req):
     with tracing.log('dispatch._rundispatch'):
         if req.ferr:
             ferr = req.ferr
         elif req.ui:
             ferr = req.ui.ferr
         else:
             ferr = procutil.stderr
 
         try:
             if not req.ui:
                 req.ui = uimod.ui.load()
             req.earlyoptions.update(_earlyparseopts(req.ui, req.args))
             if req.earlyoptions[b'traceback']:
                 req.ui.setconfig(b'ui', b'traceback', b'on', b'--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
             if req.fmsg:
                 req.ui.fmsg = req.fmsg
         except error.Abort as inst:
             ferr.write(inst.format())
             return -1
 
         msg = _formatargs(req.args)
         starttime = util.timer()
         ret = 1  # default of Python exit code on unhandled exception
         try:
             ret = _runcatch(req) or 0
         except error.ProgrammingError as inst:
             req.ui.error(_(b'** ProgrammingError: %s\n') % inst)
             if inst.hint:
                 req.ui.error(_(b'** (%s)\n') % inst.hint)
             raise
         except KeyboardInterrupt as inst:
             try:
                 if isinstance(inst, error.SignalInterrupt):
                     msg = _(b"killed!\n")
                 else:
                     msg = _(b"interrupted!\n")
                 req.ui.error(msg)
             except error.SignalInterrupt:
                 # maybe pager would quit without consuming all the output, and
                 # SIGPIPE was raised. we cannot print anything in this case.
                 pass
             except IOError as inst:
                 if inst.errno != errno.EPIPE:
                     raise
             ret = -1
         finally:
             duration = util.timer() - starttime
-            req.ui.flush()  # record blocked times
+            try:
+                req.ui.flush()  # record blocked times
+            except BaseException:
+                pass
             if req.ui.logblockedtimes:
                 req.ui._blockedtimes[b'command_duration'] = duration * 1000
                 req.ui.log(
                     b'uiblocked',
                     b'ui blocked ms\n',
                     **pycompat.strkwargs(req.ui._blockedtimes)
                 )
             return_code = ret & 255
             req.ui.log(
                 b"commandfinish",
                 b"%s exited %d after %0.2f seconds\n",
                 msg,
                 return_code,
                 duration,
                 return_code=return_code,
                 duration=duration,
                 canonical_command=req.canonical_command,
             )
             try:
                 req._runexithandlers()
             except:  # exiting, so no re-raises
                 ret = ret or -1
             # do flush again since ui.log() and exit handlers may write to ui
-            req.ui.flush()
+            try:
+                req.ui.flush()
+            except BaseException:
+                pass
         return ret
 
 
 def _runcatch(req):
     with tracing.log('dispatch._runcatch'):
 
         def catchterm(*args):
             raise error.SignalInterrupt
 
         ui = req.ui
         try:
             for name in b'SIGBREAK', b'SIGHUP', b'SIGTERM':
                 num = getattr(signal, name, None)
                 if num:
                     signal.signal(num, catchterm)
         except ValueError:
             pass  # happens if called in a thread
 
         def _runcatchfunc():
             realcmd = None
             try:
                 cmdargs = fancyopts.fancyopts(
                     req.args[:], commands.globalopts, {}
                 )
                 cmd = cmdargs[0]
                 aliases, entry = cmdutil.findcmd(cmd, commands.table, False)
                 realcmd = aliases[0]
             except (
                 error.UnknownCommand,
                 error.AmbiguousCommand,
                 IndexError,
                 getopt.GetoptError,
             ):
                 # Don't handle this here. We know the command is
                 # invalid, but all we're worried about for now is that
                 # it's not a command that server operators expect to
                 # be safe to offer to users in a sandbox.
                 pass
             if realcmd == b'serve' and b'--stdio' in cmdargs:
                 # We want to constrain 'hg serve --stdio' instances pretty
                 # closely, as many shared-ssh access tools want to grant
                 # access to run *only* 'hg -R $repo serve --stdio'. We
                 # restrict to exactly that set of arguments, and prohibit
                 # any repo name that starts with '--' to prevent
                 # shenanigans wherein a user does something like pass
                 # --debugger or --config=ui.debugger=1 as a repo
                 # name. This used to actually run the debugger.
                 if (
                     len(req.args) != 4
                     or req.args[0] != b'-R'
                     or req.args[1].startswith(b'--')
                     or req.args[2] != b'serve'
                     or req.args[3] != b'--stdio'
                 ):
                     raise error.Abort(
                         _(b'potentially unsafe serve --stdio invocation: %s')
                         % (stringutil.pprint(req.args),)
                     )
 
             try:
                 debugger = b'pdb'
                 debugtrace = {b'pdb': pdb.set_trace}
                 debugmortem = {b'pdb': pdb.post_mortem}
 
                 # read --config before doing anything else
                 # (e.g. to change trust settings for reading .hg/hgrc)
                 cfgs = _parseconfig(req.ui, req.earlyoptions[b'config'])
 
                 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=b'--config'
                         )
 
                 # developer config: ui.debugger
                 debugger = ui.config(b"ui", b"debugger")
                 debugmod = pdb
                 if not debugger or ui.plain():
                     # if we are in HGPLAIN mode, then disable custom debugging
                     debugger = b'pdb'
                 elif req.earlyoptions[b'debugger']:
                     # 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 req.earlyoptions[b'debugger']:
                     ui.warn(
                         _(
                             b"entering debugger - "
                             b"type c to continue starting hg or h for help\n"
                         )
                     )
 
                     if (
                         debugger != b'pdb'
                         and debugtrace[debugger] == debugtrace[b'pdb']
                     ):
                         ui.warn(
                             _(
                                 b"%s debugger specified "
                                 b"but its module was not found\n"
                             )
                             % debugger
                         )
                     with demandimport.deactivated():
                         debugtrace[debugger]()
                 try:
                     return _dispatch(req)
                 finally:
-                    ui.flush()
+                    try:
+                        ui.flush()  # record blocked times
+                    except BaseException:
+                        pass
             except:  # re-raises
                 # enter the debugger when we hit an exception
                 if req.earlyoptions[b'debugger']:
                     traceback.print_exc()
                     debugmortem[debugger](sys.exc_info()[2])
                 raise
 
         return _callcatch(ui, _runcatchfunc)
 
 
 def _callcatch(ui, func):
     """like scmutil.callcatch but handles more high-level exceptions about
     config parsing and commands. besides, use handlecommandexception to handle
     uncaught exceptions.
     """
     detailed_exit_code = -1
     try:
         return scmutil.callcatch(ui, func)
     except error.AmbiguousCommand as inst:
         detailed_exit_code = 10
         ui.warn(
             _(b"hg: command '%s' is ambiguous:\n    %s\n")
             % (inst.prefix, b" ".join(inst.matches))
         )
     except error.CommandError as inst:
         detailed_exit_code = 10
         if inst.command:
             ui.pager(b'help')
             msgbytes = pycompat.bytestr(inst.message)
             ui.warn(_(b"hg %s: %s\n") % (inst.command, msgbytes))
             commands.help_(ui, inst.command, full=False, command=True)
         else:
             ui.warn(_(b"hg: %s\n") % inst.message)
             ui.warn(_(b"(use 'hg help -v' for a list of global options)\n"))
     except error.UnknownCommand as inst:
         detailed_exit_code = 10
         nocmdmsg = _(b"hg: unknown command '%s'\n") % inst.command
         try:
             # check if the command is in a disabled extension
             # (but don't check for extensions themselves)
             formatted = help.formattedhelp(
                 ui, commands, inst.command, unknowncmd=True
             )
             ui.warn(nocmdmsg)
             ui.write(formatted)
         except (error.UnknownCommand, error.Abort):
             suggested = False
             if inst.all_commands:
                 sim = error.getsimilar(inst.all_commands, inst.command)
                 if sim:
                     ui.warn(nocmdmsg)
                     ui.warn(b"(%s)\n" % error.similarity_hint(sim))
                     suggested = True
             if not suggested:
                 ui.warn(nocmdmsg)
                 ui.warn(_(b"(use 'hg help' for a list of commands)\n"))
     except IOError:
         raise
     except KeyboardInterrupt:
         raise
     except:  # probably re-raises
         if not handlecommandexception(ui):
             raise
 
     if ui.configbool(b'ui', b'detailed-exit-code'):
         return detailed_exit_code
     else:
         return -1
 
 
 def aliasargs(fn, givenargs):
     args = []
     # only care about alias 'args', ignore 'args' set by extensions.wrapfunction
     if not util.safehasattr(fn, b'_origfunc'):
         args = getattr(fn, 'args', args)
     if args:
         cmd = b' '.join(map(procutil.shellquote, args))
 
         nums = []
 
         def replacer(m):
             num = int(m.group(1)) - 1
             nums.append(num)
             if num < len(givenargs):
                 return givenargs[num]
             raise error.InputError(_(b'too few arguments for command alias'))
 
         cmd = re.sub(br'\$(\d+|\$)', replacer, cmd)
         givenargs = [x for i, x in enumerate(givenargs) if i not in nums]
         args = pycompat.shlexsplit(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 "$@" (with quotes) because it's only
     # built to match prefix + patterns.
     replacemap = {b'$%d' % (i + 1): arg for i, arg in enumerate(args)}
     replacemap[b'$0'] = name
     replacemap[b'$$'] = b'$'
     replacemap[b'$@'] = b' '.join(args)
     # Typical Unix shells interpolate "$@" (with quotes) as all the positional
     # parameters, separated out into words. Emulate the same behavior here by
     # quoting the arguments individually. POSIX shells will then typically
     # tokenize each argument into exactly one word.
     replacemap[b'"$@"'] = b' '.join(procutil.shellquote(arg) for arg in args)
     # escape '\$' for regex
     regex = b'|'.join(replacemap.keys()).replace(b'$', br'\$')
     r = re.compile(regex)
     return r.sub(lambda x: replacemap[x.group()], cmd)
 
 
 class cmdalias(object):
     def __init__(self, ui, name, definition, cmdtable, source):
         self.name = self.cmd = name
         self.cmdname = b''
         self.definition = definition
         self.fn = None
         self.givenargs = []
         self.opts = []
         self.help = b''
         self.badalias = None
         self.unknowncmd = False
         self.source = source
 
         try:
             aliases, entry = cmdutil.findcmd(self.name, cmdtable)
             for alias, e in pycompat.iteritems(cmdtable):
                 if e is entry:
                     self.cmd = alias
                     break
             self.shadows = True
         except error.UnknownCommand:
             self.shadows = False
 
         if not self.definition:
             self.badalias = _(b"no definition for alias '%s'") % self.name
             return
 
         if self.definition.startswith(b'!'):
             shdef = self.definition[1:]
             self.shell = True
 
             def fn(ui, *args):
                 env = {b'HG_ARGS': b' '.join((self.name,) + args)}
 
                 def _checkvar(m):
                     if m.groups()[0] == b'$':
                         return m.group()
                     elif int(m.groups()[0]) <= len(args):
                         return m.group()
                     else:
                         ui.debug(
                             b"No argument found for substitution "
                             b"of %i variable in alias '%s' definition.\n"
                             % (int(m.groups()[0]), self.name)
                         )
                         return b''
 
                 cmd = re.sub(br'\$(\d+|\$)', _checkvar, shdef)
                 cmd = aliasinterpolate(self.name, args, cmd)
                 return ui.system(
                     cmd, environ=env, blockedtag=b'alias_%s' % self.name
                 )
 
             self.fn = fn
             self.alias = True
             self._populatehelp(ui, name, shdef, self.fn)
             return
 
         try:
             args = pycompat.shlexsplit(self.definition)
         except ValueError as inst:
             self.badalias = _(b"error in definition for alias '%s': %s") % (
                 self.name,
                 stringutil.forcebytestr(inst),
             )
             return
         earlyopts, args = _earlysplitopts(args)
         if earlyopts:
             self.badalias = _(
                 b"error in definition for alias '%s': %s may "
                 b"only be given on the command line"
             ) % (self.name, b'/'.join(pycompat.ziplist(*earlyopts)[0]))
             return
         self.cmdname = cmd = args.pop(0)
         self.givenargs = args
 
         try:
             tableentry = cmdutil.findcmd(cmd, cmdtable, False)[1]
             if len(tableentry) > 2:
                 self.fn, self.opts, cmdhelp = tableentry
             else:
                 self.fn, self.opts = tableentry
                 cmdhelp = None
 
             self.alias = True
             self._populatehelp(ui, name, cmd, self.fn, cmdhelp)
 
         except error.UnknownCommand:
             self.badalias = _(
                 b"alias '%s' resolves to unknown command '%s'"
             ) % (
                 self.name,
                 cmd,
             )
             self.unknowncmd = True
         except error.AmbiguousCommand:
             self.badalias = _(
                 b"alias '%s' resolves to ambiguous command '%s'"
             ) % (
                 self.name,
                 cmd,
             )
 
     def _populatehelp(self, ui, name, cmd, fn, defaulthelp=None):
         # confine strings to be passed to i18n.gettext()
         cfg = {}
         for k in (b'doc', b'help', b'category'):
             v = ui.config(b'alias', b'%s:%s' % (name, k), None)
             if v is None:
                 continue
             if not encoding.isasciistr(v):
                 self.badalias = _(
                     b"non-ASCII character in alias definition '%s:%s'"
                 ) % (name, k)
                 return
             cfg[k] = v
 
         self.help = cfg.get(b'help', defaulthelp or b'')
         if self.help and self.help.startswith(b"hg " + cmd):
             # drop prefix in old-style help lines so hg shows the alias
             self.help = self.help[4 + len(cmd) :]
 
         self.owndoc = b'doc' in cfg
         doc = cfg.get(b'doc', pycompat.getdoc(fn))
         if doc is not None:
             doc = pycompat.sysstr(doc)
         self.__doc__ = doc
 
         self.helpcategory = cfg.get(
             b'category', registrar.command.CATEGORY_NONE
         )
 
     @property
     def args(self):
         args = pycompat.maplist(util.expandpath, self.givenargs)
         return aliasargs(self.fn, args)
 
     def __getattr__(self, name):
         adefaults = {
             'norepo': True,
             'intents': set(),
             'optionalrepo': False,
             'inferrepo': False,
         }
         if name not in adefaults:
             raise AttributeError(name)
         if self.badalias or util.safehasattr(self, b'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 = _(b"'%s' is provided by '%s' extension") % (cmd, ext)
                 except error.UnknownCommand:
                     pass
             raise error.ConfigError(self.badalias, hint=hint)
         if self.shadows:
             ui.debug(
                 b"alias '%s' shadows command '%s'\n" % (self.name, self.cmdname)
             )
 
         ui.log(
             b'commandalias',
             b"alias '%s' expands to '%s'\n",
             self.name,
             self.definition,
         )
         if util.safehasattr(self, b'shell'):
             return self.fn(ui, *args, **opts)
         else:
             try:
                 return util.checksignature(self.fn)(ui, *args, **opts)
             except error.SignatureError:
                 args = b' '.join([self.cmdname] + self.args)
                 ui.debug(b"alias '%s' expands to '%s'\n" % (self.name, args))
                 raise
 
 
 class lazyaliasentry(object):
     """like a typical command entry (func, opts, help), but is lazy"""
 
     def __init__(self, ui, name, definition, cmdtable, source):
         self.ui = ui
         self.name = name
         self.definition = definition
         self.cmdtable = cmdtable.copy()
         self.source = source
         self.alias = True
 
     @util.propertycache
     def _aliasdef(self):
         return cmdalias(
             self.ui, self.name, self.definition, self.cmdtable, self.source
         )
 
     def __getitem__(self, n):
         aliasdef = self._aliasdef
         if n == 0:
             return aliasdef
         elif n == 1:
             return aliasdef.opts
         elif n == 2:
             return aliasdef.help
         else:
             raise IndexError
 
     def __iter__(self):
         for i in range(3):
             yield self[i]
 
     def __len__(self):
         return 3
 
 
 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(b'alias', ignoresub=True):
         try:
             if cmdtable[alias].definition == definition:
                 continue
         except (KeyError, AttributeError):
             # definition might not exist or it might not be a cmdalias
             pass
 
         source = ui.configsource(b'alias', alias)
         entry = lazyaliasentry(ui, alias, definition, cmdtable, source)
         cmdtable[alias] = entry
 
 
 def _parse(ui, args):
     options = {}
     cmdoptions = {}
 
     try:
         args = fancyopts.fancyopts(args, commands.globalopts, options)
     except getopt.GetoptError as inst:
         raise error.CommandError(None, stringutil.forcebytestr(inst))
 
     if args:
         cmd, args = args[0], args[1:]
         aliases, entry = cmdutil.findcmd(
             cmd, commands.table, ui.configbool(b"ui", b"strict")
         )
         cmd = aliases[0]
         args = aliasargs(entry[0], args)
         defaults = ui.config(b"defaults", cmd)
         if defaults:
             args = (
                 pycompat.maplist(util.expandpath, pycompat.shlexsplit(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, gnu=True)
     except getopt.GetoptError as inst:
         raise error.CommandError(cmd, stringutil.forcebytestr(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(b'=', 1)]
             section, name = name.split(b'.', 1)
             if not section or not name:
                 raise IndexError
             ui.setconfig(section, name, value, b'--config')
             configs.append((section, name, value))
         except (IndexError, ValueError):
             raise error.InputError(
                 _(
                     b'malformed --config option: %r '
                     b'(use --config section.name=value)'
                 )
                 % pycompat.bytestr(cfg)
             )
 
     return configs
 
 
 def _earlyparseopts(ui, args):
     options = {}
     fancyopts.fancyopts(
         args,
         commands.globalopts,
         options,
         gnu=not ui.plain(b'strictflags'),
         early=True,
         optaliases={b'repository': [b'repo']},
     )
     return options
 
 
 def _earlysplitopts(args):
     """Split args into a list of possible early options and remainder args"""
     shortoptions = b'R:'
     # TODO: perhaps 'debugger' should be included
     longoptions = [b'cwd=', b'repository=', b'repo=', b'config=']
     return fancyopts.earlygetopt(
         args, shortoptions, longoptions, gnu=True, keepsep=True
     )
 
 
 def runcommand(lui, repo, cmd, fullargs, ui, options, d, cmdpats, cmdoptions):
     # run pre-hook, and abort if it fails
     hook.hook(
         lui,
         repo,
         b"pre-%s" % cmd,
         True,
         args=b" ".join(fullargs),
         pats=cmdpats,
         opts=cmdoptions,
     )
     try:
         ret = _runcommand(ui, options, cmd, d)
         # run post-hook, passing command result
         hook.hook(
             lui,
             repo,
             b"post-%s" % cmd,
             False,
             args=b" ".join(fullargs),
             result=ret,
             pats=cmdpats,
             opts=cmdoptions,
         )
     except Exception:
         # run failure hook and re-raise
         hook.hook(
             lui,
             repo,
             b"fail-%s" % cmd,
             False,
             args=b" ".join(fullargs),
             pats=cmdpats,
             opts=cmdoptions,
         )
         raise
     return ret
 
 
 def _readsharedsourceconfig(ui, path):
     """if the current repository is shared one, this tries to read
     .hg/hgrc of shared source if we are in share-safe mode
 
     Config read is loaded into the ui object passed
 
     This should be called before reading .hg/hgrc or the main repo
     as that overrides config set in shared source"""
     try:
         with open(os.path.join(path, b".hg", b"requires"), "rb") as fp:
             requirements = set(fp.read().splitlines())
             if not (
                 requirementsmod.SHARESAFE_REQUIREMENT in requirements
                 and requirementsmod.SHARED_REQUIREMENT in requirements
             ):
                 return
             hgvfs = vfs.vfs(os.path.join(path, b".hg"))
             sharedvfs = localrepo._getsharedvfs(hgvfs, requirements)
             root = sharedvfs.base
             ui.readconfig(sharedvfs.join(b"hgrc"), root)
     except IOError:
         pass
 
 
 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 = encoding.getcwd()
         except OSError as e:
             raise error.Abort(
                 _(b"error getting current working directory: %s")
                 % encoding.strtolocal(e.strerror)
             )
 
     path = cmdutil.findrepo(wd) or b""
     if not path:
         lui = ui
     else:
         lui = ui.copy()
         if rcutil.use_repo_hgrc():
             _readsharedsourceconfig(lui, path)
             lui.readconfig(os.path.join(path, b".hg", b"hgrc"), path)
             lui.readconfig(os.path.join(path, b".hg", b"hgrc-not-shared"), path)
 
     if rpath:
         path = urlutil.get_clone_path(lui, rpath)[0]
         lui = ui.copy()
         if rcutil.use_repo_hgrc():
             _readsharedsourceconfig(lui, path)
             lui.readconfig(os.path.join(path, b".hg", b"hgrc"), path)
             lui.readconfig(os.path.join(path, b".hg", b"hgrc-not-shared"), path)
 
     return path, lui
 
 
 def _checkshellalias(lui, ui, args):
     """Return the function to run the shell alias, if it is required"""
     options = {}
 
     try:
         args = fancyopts.fancyopts(args, commands.globalopts, options)
     except getopt.GetoptError:
         return
 
     if not args:
         return
 
     cmdtable = commands.table
 
     cmd = args[0]
     try:
         strict = ui.configbool(b"ui", b"strict")
         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, b'shell'):
         # shell alias shouldn't receive early options which are consumed by hg
         _earlyopts, args = _earlysplitopts(args)
         d = lambda: fn(ui, *args[1:])
         return lambda: runcommand(
             lui, None, cmd, args[:1], ui, options, d, [], {}
         )
 
 
 def _dispatch(req):
     args = req.args
     ui = req.ui
 
     # check for cwd
     cwd = req.earlyoptions[b'cwd']
     if cwd:
         os.chdir(cwd)
 
     rpath = req.earlyoptions[b'repository']
     path, lui = _getlocal(ui, rpath)
 
     uis = {ui, lui}
 
     if req.repo:
         uis.add(req.repo.ui)
 
     if (
         req.earlyoptions[b'verbose']
         or req.earlyoptions[b'debug']
         or req.earlyoptions[b'quiet']
     ):
         for opt in (b'verbose', b'debug', b'quiet'):
             val = pycompat.bytestr(bool(req.earlyoptions[opt]))
             for ui_ in uis:
                 ui_.setconfig(b'ui', opt, val, b'--' + opt)
 
     if req.earlyoptions[b'profile']:
         for ui_ in uis:
             ui_.setconfig(b'profiling', b'enabled', b'true', b'--profile')
     elif req.earlyoptions[b'profile'] is False:
         # Check for it being set already, so that we don't pollute the config
         # with this when using chg in the very common case that it's not
         # enabled.
         if lui.configbool(b'profiling', b'enabled'):
             # Only do this on lui so that `chg foo` with a user config setting
             # profiling.enabled=1 still shows profiling information (chg will
             # specify `--no-profile` when `hg serve` is starting up, we don't
             # want that to propagate to every later invocation).
             lui.setconfig(b'profiling', b'enabled', b'false', b'--no-profile')
 
     profile = lui.configbool(b'profiling', b'enabled')
     with profiling.profile(lui, enabled=profile) as profiler:
         # Configure extensions in phases: uisetup, extsetup, cmdtable, and
         # reposetup
         extensions.loadall(lui)
         # Propagate any changes to lui.__class__ by extensions
         ui.__class__ = lui.__class__
 
         # (uisetup and extsetup are handled in extensions.loadall)
 
         # (reposetup is handled in hg.repository)
 
         addaliases(lui, commands.table)
 
         # All aliases and commands are completely defined, now.
         # Check abbreviation/ambiguity of shell alias.
         shellaliasfn = _checkshellalias(lui, ui, args)
         if shellaliasfn:
             # no additional configs will be set, set up the ui instances
             for ui_ in uis:
                 extensions.populateui(ui_)
             return shellaliasfn()
 
         # check for fallback encoding
         fallback = lui.config(b'ui', b'fallbackencoding')
         if fallback:
             encoding.fallbackencoding = fallback
 
         fullargs = args
         cmd, func, args, options, cmdoptions = _parse(lui, args)
 
         # store the canonical command name in request object for later access
         req.canonical_command = cmd
 
         if options[b"config"] != req.earlyoptions[b"config"]:
             raise error.InputError(_(b"option --config may not be abbreviated"))
         if options[b"cwd"] != req.earlyoptions[b"cwd"]:
             raise error.InputError(_(b"option --cwd may not be abbreviated"))
         if options[b"repository"] != req.earlyoptions[b"repository"]:
             raise error.InputError(
                 _(
                     b"option -R has to be separated from other options (e.g. not "
                     b"-qR) and --repository may only be abbreviated as --repo"
                 )
             )
         if options[b"debugger"] != req.earlyoptions[b"debugger"]:
             raise error.InputError(
                 _(b"option --debugger may not be abbreviated")
             )
         # don't validate --profile/--traceback, which can be enabled from now
 
         if options[b"encoding"]:
             encoding.encoding = options[b"encoding"]
         if options[b"encodingmode"]:
             encoding.encodingmode = options[b"encodingmode"]
         if options[b"time"]:
 
             def get_times():
                 t = os.times()
                 if t[4] == 0.0:
                     # Windows leaves this as zero, so use time.perf_counter()
                     t = (t[0], t[1], t[2], t[3], util.timer())
                 return t
 
             s = get_times()
 
             def print_time():
                 t = get_times()
                 ui.warn(
                     _(b"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],
                     )
                 )
 
             ui.atexit(print_time)
         if options[b"profile"]:
             profiler.start()
 
         # if abbreviated version of this were used, take them in account, now
         if options[b'verbose'] or options[b'debug'] or options[b'quiet']:
             for opt in (b'verbose', b'debug', b'quiet'):
                 if options[opt] == req.earlyoptions[opt]:
                     continue
                 val = pycompat.bytestr(bool(options[opt]))
                 for ui_ in uis:
                     ui_.setconfig(b'ui', opt, val, b'--' + opt)
 
         if options[b'traceback']:
             for ui_ in uis:
                 ui_.setconfig(b'ui', b'traceback', b'on', b'--traceback')
 
         if options[b'noninteractive']:
             for ui_ in uis:
                 ui_.setconfig(b'ui', b'interactive', b'off', b'-y')
 
         if cmdoptions.get(b'insecure', False):
             for ui_ in uis:
                 ui_.insecureconnections = True
 
         # setup color handling before pager, because setting up pager
         # might cause incorrect console information
         coloropt = options[b'color']
         for ui_ in uis:
             if coloropt:
                 ui_.setconfig(b'ui', b'color', coloropt, b'--color')
             color.setup(ui_)
 
         if stringutil.parsebool(options[b'pager']):
             # ui.pager() expects 'internal-always-' prefix in this case
             ui.pager(b'internal-always-' + cmd)
         elif options[b'pager'] != b'auto':
             for ui_ in uis:
                 ui_.disablepager()
 
         # configs are fully loaded, set up the ui instances
         for ui_ in uis:
             extensions.populateui(ui_)
 
         if options[b'version']:
             return commands.version_(ui)
         if options[b'help']:
             return commands.help_(ui, cmd, command=cmd is not None)
         elif not cmd:
             return commands.help_(ui, b'shortlist')
 
         repo = None
         cmdpats = args[:]
         assert func is not None  # help out pytype
         if not 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
                 repo.ui.fmsg = ui.fmsg
             else:
                 try:
                     repo = hg.repository(
                         ui,
                         path=path,
                         presetupfuncs=req.prereposetups,
                         intents=func.intents,
                     )
                     if not repo.local():
                         raise error.InputError(
                             _(b"repository '%s' is not local") % path
                         )
                     repo.ui.setconfig(
                         b"bundle", b"mainreporoot", repo.root, b'repo'
                     )
                 except error.RequirementError:
                     raise
                 except error.RepoError:
                     if rpath:  # invalid -R path
                         raise
                     if not func.optionalrepo:
                         if func.inferrepo and args and not path:
                             # try to infer -R from command args
                             repos = pycompat.maplist(cmdutil.findrepo, args)
                             guess = repos[0]
                             if guess and repos.count(guess) == len(repos):
                                 req.args = [b'--repository', guess] + fullargs
                                 req.earlyoptions[b'repository'] = guess
                                 return _dispatch(req)
                         if not path:
                             raise error.InputError(
                                 _(
                                     b"no repository found in"
                                     b" '%s' (.hg not found)"
                                 )
                                 % encoding.getcwd()
                             )
                         raise
             if repo:
                 ui = repo.ui
                 if options[b'hidden']:
                     repo = repo.unfiltered()
             args.insert(0, repo)
         elif rpath:
             ui.warn(_(b"warning: --repository ignored\n"))
 
         msg = _formatargs(fullargs)
         ui.log(b"command", b'%s\n', msg)
         strcmdopt = pycompat.strkwargs(cmdoptions)
         d = lambda: util.checksignature(func)(ui, *args, **strcmdopt)
         try:
             return runcommand(
                 lui, repo, cmd, fullargs, ui, options, d, cmdpats, cmdoptions
             )
         finally:
             if repo and repo != req.repo:
                 repo.close()
 
 
 def _runcommand(ui, options, cmd, cmdfunc):
     """Run a command function, possibly with profiling enabled."""
     try:
         with tracing.log("Running %s command" % cmd):
             return cmdfunc()
     except error.SignatureError:
         raise error.CommandError(cmd, _(b'invalid arguments'))
 
 
 def _exceptionwarning(ui):
     """Produce a warning message for the current active exception"""
 
     # 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, b'', b''
     if ui.config(b'ui', b'supportcontact') is None:
         for name, mod in extensions.extensions():
             # 'testedwith' should be bytes, but not all extensions are ported
             # to py3 and we don't want UnicodeException because of that.
             testedwith = stringutil.forcebytestr(
                 getattr(mod, 'testedwith', b'')
             )
             version = extensions.moduleversion(mod)
             report = getattr(mod, 'buglink', _(b'the extension author.'))
             if not testedwith.strip():
                 # We found an untested extension. It's likely the culprit.
                 worst = name, b'unknown', report, version
                 break
 
             # Never blame on extensions bundled with Mercurial.
             if extensions.ismoduleinternal(mod):
                 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, version
     if worst[0] is not None:
         name, testedwith, report, version = worst
         if not isinstance(testedwith, (bytes, str)):
             testedwith = b'.'.join(
                 [stringutil.forcebytestr(c) for c in testedwith]
             )
         extver = version or _(b"(version N/A)")
         warning = _(
             b'** Unknown exception encountered with '
             b'possibly-broken third-party extension "%s" %s\n'
             b'** which supports versions %s of Mercurial.\n'
             b'** Please disable "%s" and try your action again.\n'
             b'** If that fixes the bug please report it to %s\n'
         ) % (name, extver, testedwith, name, stringutil.forcebytestr(report))
     else:
         bugtracker = ui.config(b'ui', b'supportcontact')
         if bugtracker is None:
             bugtracker = _(b"https://mercurial-scm.org/wiki/BugTracker")
         warning = (
             _(
                 b"** unknown exception encountered, "
                 b"please report by visiting\n** "
             )
             + bugtracker
             + b'\n'
         )
     sysversion = pycompat.sysbytes(sys.version).replace(b'\n', b'')
 
     def ext_with_ver(x):
         ext = x[0]
         ver = extensions.moduleversion(x[1])
         if ver:
             ext += b' ' + ver
         return ext
 
     warning += (
         (_(b"** Python %s\n") % sysversion)
         + (_(b"** Mercurial Distributed SCM (version %s)\n") % util.version())
         + (
             _(b"** Extensions loaded: %s\n")
             % b", ".join(
                 [ext_with_ver(x) for x in sorted(extensions.extensions())]
             )
         )
     )
     return warning
 
 
 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.
     """
     warning = _exceptionwarning(ui)
     ui.log(
         b"commandexception",
         b"%s\n%s\n",
         warning,
         pycompat.sysbytes(traceback.format_exc()),
     )
     ui.warn(warning)
     return False  # re-raise the exception

tests/test-pager.t

@@ -1,438 +1,432 b''
   $ cat >> fakepager.py <<EOF
   > import sys
   > printed = False
   > for line in sys.stdin:
   >     sys.stdout.write('paged! %r\n' % line)
   >     printed = True
   > if not printed:
   >     sys.stdout.write('paged empty output!\n')
   > EOF
 
 Enable ui.formatted because pager won't fire without it, and set up
 pager and tell it to use our fake pager that lets us see when the
 pager was running.
   $ cat >> $HGRCPATH <<EOF
   > [ui]
   > formatted = yes
   > color = no
   > [pager]
   > pager = "$PYTHON" $TESTTMP/fakepager.py
   > EOF
 
   $ hg init repo
   $ cd repo
   $ echo a >> a
   $ hg add a
   $ hg ci -m 'add a'
   $ for x in `"$PYTHON" $TESTDIR/seq.py 1 10`; do
   >   echo a $x >> a
   >   hg ci -m "modify a $x"
   > done
 
 By default diff and log are paged, but id is not:
 
   $ hg diff -c 2 --pager=yes
   paged! 'diff -r f4be7687d414 -r bce265549556 a\n'
   paged! '--- a/a\tThu Jan 01 00:00:00 1970 +0000\n'
   paged! '+++ b/a\tThu Jan 01 00:00:00 1970 +0000\n'
   paged! '@@ -1,2 +1,3 @@\n'
   paged! ' a\n'
   paged! ' a 1\n'
   paged! '+a 2\n'
 
   $ hg log --limit 2
   paged! 'changeset:   10:46106edeeb38\n'
   paged! 'tag:         tip\n'
   paged! 'user:        test\n'
   paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
   paged! 'summary:     modify a 10\n'
   paged! '\n'
   paged! 'changeset:   9:6dd8ea7dd621\n'
   paged! 'user:        test\n'
   paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
   paged! 'summary:     modify a 9\n'
   paged! '\n'
 
   $ hg id
   46106edeeb38 tip
 
 We can control the pager from the config
 
   $ hg log --limit 1 --config 'ui.paginate=False'
   changeset:   10:46106edeeb38
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     modify a 10
   
   $ hg log --limit 1 --config 'ui.paginate=0'
   changeset:   10:46106edeeb38
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     modify a 10
   
   $ hg log --limit 1 --config 'ui.paginate=1'
   paged! 'changeset:   10:46106edeeb38\n'
   paged! 'tag:         tip\n'
   paged! 'user:        test\n'
   paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
   paged! 'summary:     modify a 10\n'
   paged! '\n'
 
 explicit --pager=on should take precedence over other configurations
 (issue5580)
 
   $ cat >> $HGRCPATH <<EOF
   > [ui]
   > paginate = false
   > EOF
   $ hg log --limit 1 --pager=on
   paged! 'changeset:   10:46106edeeb38\n'
   paged! 'tag:         tip\n'
   paged! 'user:        test\n'
   paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
   paged! 'summary:     modify a 10\n'
   paged! '\n'
 
   $ cat >> $HGRCPATH <<EOF
   > [ui]
   > # true is default value of ui.paginate
   > paginate = true
   > EOF
   $ hg log --limit 1 --pager=off
   changeset:   10:46106edeeb38
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     modify a 10
   
 
 We can enable the pager on id:
 
 BROKEN: should be paged
   $ hg --config pager.attend-id=yes id
   46106edeeb38 tip
 
 Setting attend-$COMMAND to a false value works, even with pager in
 core:
   $ hg --config pager.attend-diff=no diff -c 2
   diff -r f4be7687d414 -r bce265549556 a
   --- a/a	Thu Jan 01 00:00:00 1970 +0000
   +++ b/a	Thu Jan 01 00:00:00 1970 +0000
   @@ -1,2 +1,3 @@
    a
    a 1
   +a 2
 
 Command aliases should have same behavior as main command
 
   $ hg history --limit 2
   paged! 'changeset:   10:46106edeeb38\n'
   paged! 'tag:         tip\n'
   paged! 'user:        test\n'
   paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
   paged! 'summary:     modify a 10\n'
   paged! '\n'
   paged! 'changeset:   9:6dd8ea7dd621\n'
   paged! 'user:        test\n'
   paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
   paged! 'summary:     modify a 9\n'
   paged! '\n'
 
 Abbreviated command alias should also be paged
 
   $ hg hist -l 1
   paged! 'changeset:   10:46106edeeb38\n'
   paged! 'tag:         tip\n'
   paged! 'user:        test\n'
   paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
   paged! 'summary:     modify a 10\n'
   paged! '\n'
 
 Attend for an abbreviated command does not work
 
   $ hg --config pager.attend-ident=true ident
   46106edeeb38 tip
 
   $ hg --config extensions.pager= --config pager.attend-ident=true ident
   46106edeeb38 tip
 
 Pager should not start if stdout is not a tty.
 
   $ hg log -l1 -q --config ui.formatted=False
   10:46106edeeb38
 
 Pager should be disabled if pager.pager is empty (otherwise the output would
 be silently lost.)
 
   $ hg log -l1 -q --config pager.pager=
   10:46106edeeb38
 
 Pager with color enabled allows colors to come through by default,
 even though stdout is no longer a tty.
   $ cat >> $HGRCPATH <<EOF
   > [ui]
   > color = always
   > [color]
   > mode = ansi
   > EOF
   $ hg log --limit 3
   paged! '\x1b[0;33mchangeset:   10:46106edeeb38\x1b[0m\n'
   paged! 'tag:         tip\n'
   paged! 'user:        test\n'
   paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
   paged! 'summary:     modify a 10\n'
   paged! '\n'
   paged! '\x1b[0;33mchangeset:   9:6dd8ea7dd621\x1b[0m\n'
   paged! 'user:        test\n'
   paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
   paged! 'summary:     modify a 9\n'
   paged! '\n'
   paged! '\x1b[0;33mchangeset:   8:cff05a6312fe\x1b[0m\n'
   paged! 'user:        test\n'
   paged! 'date:        Thu Jan 01 00:00:00 1970 +0000\n'
   paged! 'summary:     modify a 8\n'
   paged! '\n'
 
 #if no-chg
 An invalid pager command name is reported sensibly if we don't have to
 use shell=True in the subprocess call:
   $ hg log --limit 3 --config pager.pager=this-command-better-never-exist
   missing pager command 'this-command-better-never-exist', skipping pager
   \x1b[0;33mchangeset:   10:46106edeeb38\x1b[0m (esc)
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     modify a 10
   
   \x1b[0;33mchangeset:   9:6dd8ea7dd621\x1b[0m (esc)
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     modify a 9
   
   \x1b[0;33mchangeset:   8:cff05a6312fe\x1b[0m (esc)
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     modify a 8
   
 #endif
 
 A complicated pager command gets worse behavior. Bonus points if you can
-improve this. Windows apparently does this better, but only sometimes?
-#if windows
+improve this.
   $ hg log --limit 3 \
   >   --config pager.pager='this-command-better-never-exist --seriously' \
   >  2>/dev/null || true
   \x1b[0;33mchangeset:   10:46106edeeb38\x1b[0m (esc) (?)
   tag:         tip (?)
   user:        test (?)
   date:        Thu Jan 01 00:00:00 1970 +0000 (?)
   summary:     modify a 10 (?)
    (?)
   \x1b[0;33mchangeset:   9:6dd8ea7dd621\x1b[0m (esc) (?)
   user:        test (?)
   date:        Thu Jan 01 00:00:00 1970 +0000 (?)
   summary:     modify a 9 (?)
    (?)
   \x1b[0;33mchangeset:   8:cff05a6312fe\x1b[0m (esc) (?)
   user:        test (?)
   date:        Thu Jan 01 00:00:00 1970 +0000 (?)
   summary:     modify a 8 (?)
    (?)
-#else
-  $ hg log --limit 3 \
-  >   --config pager.pager='this-command-better-never-exist --seriously' \
-  >  2>/dev/null || true
-#endif
 
 Pager works with shell aliases.
 
   $ cat >> $HGRCPATH <<EOF
   > [alias]
   > echoa = !echo a
   > EOF
 
   $ hg echoa
   a
 BROKEN: should be paged
   $ hg --config pager.attend-echoa=yes echoa
   a
 
 Pager works with hg aliases including environment variables.
 
   $ cat >> $HGRCPATH <<'EOF'
   > [alias]
   > printa = log -T "$A\n" -r 0
   > EOF
 
   $ A=1 hg --config pager.attend-printa=yes printa
   paged! '1\n'
   $ A=2 hg --config pager.attend-printa=yes printa
   paged! '2\n'
 
 Something that's explicitly attended is still not paginated if the
 pager is globally set to off using a flag:
   $ A=2 hg --config pager.attend-printa=yes printa --pager=no
   2
 
 Pager should not override the exit code of other commands
 
   $ cat >> $TESTTMP/fortytwo.py <<'EOF'
   > from mercurial import commands, registrar
   > cmdtable = {}
   > command = registrar.command(cmdtable)
   > @command(b'fortytwo', [], b'fortytwo', norepo=True)
   > def fortytwo(ui, *opts):
   >     ui.write(b'42\n')
   >     return 42
   > EOF
 
   $ cat >> $HGRCPATH <<'EOF'
   > [extensions]
   > fortytwo = $TESTTMP/fortytwo.py
   > EOF
 
   $ hg fortytwo --pager=on
   paged! '42\n'
   [42]
 
 A command that asks for paging using ui.pager() directly works:
   $ hg blame a
   paged! ' 0: a\n'
   paged! ' 1: a 1\n'
   paged! ' 2: a 2\n'
   paged! ' 3: a 3\n'
   paged! ' 4: a 4\n'
   paged! ' 5: a 5\n'
   paged! ' 6: a 6\n'
   paged! ' 7: a 7\n'
   paged! ' 8: a 8\n'
   paged! ' 9: a 9\n'
   paged! '10: a 10\n'
 but not with HGPLAIN
   $ HGPLAIN=1 hg blame a
    0: a
    1: a 1
    2: a 2
    3: a 3
    4: a 4
    5: a 5
    6: a 6
    7: a 7
    8: a 8
    9: a 9
   10: a 10
 explicit flags work too:
   $ hg blame --pager=no a
    0: a
    1: a 1
    2: a 2
    3: a 3
    4: a 4
    5: a 5
    6: a 6
    7: a 7
    8: a 8
    9: a 9
   10: a 10
 
 A command with --output option:
 
   $ hg cat -r0 a
   paged! 'a\n'
   $ hg cat -r0 a --output=-
   paged! 'a\n'
   $ hg cat -r0 a --output=out
 
   $ hg export -r0
   paged! '# HG changeset patch\n'
   paged! '# User test\n'
   paged! '# Date 0 0\n'
   paged! '#      Thu Jan 01 00:00:00 1970 +0000\n'
   paged! '# Node ID 1f0dee641bb7258c56bd60e93edfa2405381c41e\n'
   paged! '# Parent  0000000000000000000000000000000000000000\n'
   paged! 'add a\n'
   paged! '\n'
   paged! '\x1b[0;1mdiff -r 000000000000 -r 1f0dee641bb7 a\x1b[0m\n'
   paged! '\x1b[0;31;1m--- /dev/null\tThu Jan 01 00:00:00 1970 +0000\x1b[0m\n'
   paged! '\x1b[0;32;1m+++ b/a\tThu Jan 01 00:00:00 1970 +0000\x1b[0m\n'
   paged! '\x1b[0;35m@@ -0,0 +1,1 @@\x1b[0m\n'
   paged! '\x1b[0;32m+a\x1b[0m\n'
   $ hg export -r0 -o -
   paged! '# HG changeset patch\n'
   paged! '# User test\n'
   paged! '# Date 0 0\n'
   paged! '#      Thu Jan 01 00:00:00 1970 +0000\n'
   paged! '# Node ID 1f0dee641bb7258c56bd60e93edfa2405381c41e\n'
   paged! '# Parent  0000000000000000000000000000000000000000\n'
   paged! 'add a\n'
   paged! '\n'
   paged! '\x1b[0;1mdiff -r 000000000000 -r 1f0dee641bb7 a\x1b[0m\n'
   paged! '\x1b[0;31;1m--- /dev/null\tThu Jan 01 00:00:00 1970 +0000\x1b[0m\n'
   paged! '\x1b[0;32;1m+++ b/a\tThu Jan 01 00:00:00 1970 +0000\x1b[0m\n'
   paged! '\x1b[0;35m@@ -0,0 +1,1 @@\x1b[0m\n'
   paged! '\x1b[0;32m+a\x1b[0m\n'
   $ hg export -r0 -o out
 
   $ rm out
 
 Put annotate in the ignore list for pager:
   $ cat >> $HGRCPATH <<EOF
   > [pager]
   > ignore = annotate
   > EOF
   $ hg blame a
    0: a
    1: a 1
    2: a 2
    3: a 3
    4: a 4
    5: a 5
    6: a 6
    7: a 7
    8: a 8
    9: a 9
   10: a 10
 
 During pushbuffer, pager should not start:
   $ cat > $TESTTMP/pushbufferpager.py <<EOF
   > def uisetup(ui):
   >     ui.pushbuffer()
   >     ui.pager(b'mycmd')
   >     ui.write(b'content\n')
   >     ui.write(ui.popbuffer())
   > EOF
 
   $ echo append >> a
   $ hg --config extensions.pushbuffer=$TESTTMP/pushbufferpager.py status --color=off
   content
   paged! 'M a\n'
 
 Environment variables like LESS and LV are set automatically:
   $ cat > $TESTTMP/printlesslv.py <<EOF
   > from __future__ import absolute_import
   > import os
   > import sys
   > sys.stdin.read()
   > for name in ['LESS', 'LV']:
   >     sys.stdout.write(('%s=%s\n') % (name, os.environ.get(name, '-')))
   > sys.stdout.flush()
   > EOF
 
   $ cat >> $HGRCPATH <<EOF
   > [alias]
   > noop = log -r 0 -T ''
   > [ui]
   > formatted=1
   > [pager]
   > pager = "$PYTHON" $TESTTMP/printlesslv.py
   > EOF
   $ unset LESS
   $ unset LV
   $ hg noop --pager=on
   LESS=FRX
   LV=-c
   $ LESS=EFGH hg noop --pager=on
   LESS=EFGH
   LV=-c