view tests/test-devel-warnings.t @ 50195:11e6eee4b063

transaction: use the standard transaction mechanism to backup branch

Branch is a bit special :
- It currently does not collaborate with the transaction (or any scoping) for
  writing (this is bad)
- It can change without the lock being taken (it is protected by `wlock`)

So we rely on the same mechanism as for the backup of the other dirstate file:
- we only do a backup if we hold the wlock
- we force a backup though the transaction


Since "branch" write does not collaborate with the transaction, we cannot back
it up "at the last minute" as we do for the dirstate. We have to back it up
"upfront". Since we have a backup, the transaction is no longer doing its
"quick_abort" and get noisy. Which is quite annoying. To work around this, and
to avoid jumping in yet-another-rabbit-hole of "getting branch written
properly", I am doing horrible things to the transaction in the meantime.
We should be able to get this code go away during the next cycle.

In the meantime, I prefer to take this small stop so that we stop abusing the
"journal" and "undo" mechanism instead of the proper backup mechanism of the
transaction.


Also note that this change regress the warning message for the legacy fallback
introduced in 2008 when issue902 got fixed in dd5a501cb97f (Mercurial 1.0).

I feel like this is fine as issue 902 remains fixed, and this would only affect
people deploying a mix of 15 year old Mercurial and modern mercurial, and using
branch and rollback extensively.

  $ cat << EOF > buggylocking.py
  > """A small extension that tests our developer warnings
  > """
  > 
  > from mercurial import error, registrar, repair, util
  > 
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > 
  > @command(b'buggylocking', [], '')
  > def buggylocking(ui, repo):
  >     lo = repo.lock()
  >     wl = repo.wlock()
  >     wl.release()
  >     lo.release()
  > 
  > @command(b'buggytransaction', [], '')
  > def buggylocking(ui, repo):
  >     tr = repo.transaction(b'buggy')
  >     # make sure we rollback the transaction as we don't want to rely on the__del__
  >     tr.release()
  > 
  > @command(b'properlocking', [], '')
  > def properlocking(ui, repo):
  >     """check that reentrance is fine"""
  >     wl = repo.wlock()
  >     lo = repo.lock()
  >     tr = repo.transaction(b'proper')
  >     tr2 = repo.transaction(b'proper')
  >     lo2 = repo.lock()
  >     wl2 = repo.wlock()
  >     wl2.release()
  >     lo2.release()
  >     tr2.close()
  >     tr.close()
  >     lo.release()
  >     wl.release()
  > 
  > @command(b'nowaitlocking', [], '')
  > def nowaitlocking(ui, repo):
  >     lo = repo.lock()
  >     wl = repo.wlock(wait=False)
  >     wl.release()
  >     lo.release()
  > 
  > @command(b'no-wlock-write', [], '')
  > def nowlockwrite(ui, repo):
  >     with repo.vfs(b'branch', b'a'):
  >         pass
  > 
  > @command(b'no-lock-write', [], '')
  > def nolockwrite(ui, repo):
  >     with repo.svfs(b'fncache', b'a'):
  >         pass
  > 
  > @command(b'stripintr', [], '')
  > def stripintr(ui, repo):
  >     lo = repo.lock()
  >     tr = repo.transaction(b'foobar')
  >     try:
  >         repair.strip(repo.ui, repo, [repo[b'.'].node()])
  >     finally:
  >         lo.release()
  > @command(b'oldanddeprecated', [], '')
  > def oldanddeprecated(ui, repo):
  >     """test deprecation warning API"""
  >     def foobar(ui):
  >         ui.deprecwarn(b'foorbar is deprecated, go shopping', b'42.1337')
  >     foobar(ui)
  > @command(b'nouiwarning', [], '')
  > def nouiwarning(ui, repo):
  >     util.nouideprecwarn(b'this is a test', b'13.37')
  > @command(b'programmingerror', [], '')
  > def programmingerror(ui, repo):
  >     raise error.ProgrammingError(b'something went wrong', hint=b'try again')
  > EOF

  $ cat << EOF >> $HGRCPATH
  > [extensions]
  > buggylocking=$TESTTMP/buggylocking.py
  > mock=$TESTDIR/mockblackbox.py
  > blackbox=
  > [devel]
  > all-warnings=1
  > [blackbox]
  > track = command, commandexception, commandfinish, develwarn
  > EOF

  $ hg init lock-checker
  $ cd lock-checker
  $ hg buggylocking
  devel-warn: "wlock" acquired after "lock" at: $TESTTMP/buggylocking.py:* (buggylocking) (glob)
  $ cat << EOF >> $HGRCPATH
  > [devel]
  > all=0
  > check-locks=1
  > EOF
  $ hg buggylocking
  devel-warn: "wlock" acquired after "lock" at: $TESTTMP/buggylocking.py:* (buggylocking) (glob)
#if no-chg no-pyoxidizer
  $ hg buggylocking --traceback
  devel-warn: "wlock" acquired after "lock" at:
   */hg:* in <module> (glob) (?)
   */mercurial/dispatch.py:* in run (glob)
   */mercurial/dispatch.py:* in dispatch (glob)
   */mercurial/dispatch.py:* in _rundispatch (glob)
   */mercurial/dispatch.py:* in _runcatch (glob)
   */mercurial/dispatch.py:* in _callcatch (glob)
   */mercurial/scmutil.py* in callcatch (glob)
   */mercurial/dispatch.py:* in _runcatchfunc (glob)
   */mercurial/dispatch.py:* in _dispatch (glob)
   */mercurial/dispatch.py:* in runcommand (glob)
   */mercurial/dispatch.py:* in _runcommand (glob)
   */mercurial/dispatch.py:* in <lambda> (glob)
   */mercurial/util.py:* in check (glob)
   $TESTTMP/buggylocking.py:* in buggylocking (glob)
#endif
#if chg no-pyoxidizer
  $ hg buggylocking --traceback
  devel-warn: "wlock" acquired after "lock" at:
   */hg:* in <module> (glob) (?)
   */mercurial/dispatch.py:* in run (glob)
   */mercurial/dispatch.py:* in dispatch (glob)
   */mercurial/dispatch.py:* in _rundispatch (glob)
   */mercurial/dispatch.py:* in _runcatch (glob)
   */mercurial/dispatch.py:* in _callcatch (glob)
   */mercurial/scmutil.py:* in callcatch (glob)
   */mercurial/dispatch.py:* in _runcatchfunc (glob)
   */mercurial/dispatch.py:* in _dispatch (glob)
   */mercurial/dispatch.py:* in runcommand (glob)
   */mercurial/dispatch.py:* in _runcommand (glob)
   */mercurial/dispatch.py:* in <lambda> (glob)
   */mercurial/util.py:* in check (glob)
   */mercurial/commands.py:* in serve (glob)
   */mercurial/server.py:* in runservice (glob)
   */mercurial/commandserver.py:* in run (glob)
   */mercurial/commandserver.py:* in _mainloop (glob)
   */mercurial/commandserver.py:* in _acceptnewconnection (glob)
   */mercurial/commandserver.py:* in _runworker (glob)
   */mercurial/commandserver.py:* in _serverequest (glob)
   */mercurial/commandserver.py:* in serve (glob)
   */mercurial/commandserver.py:* in serveone (glob)
   */mercurial/chgserver.py:* in runcommand (glob)
   */mercurial/commandserver.py:* in runcommand (glob)
   */mercurial/commandserver.py:* in _dispatchcommand (glob)
   */mercurial/dispatch.py:* in dispatch (glob)
   */mercurial/dispatch.py:* in _rundispatch (glob)
   */mercurial/dispatch.py:* in _runcatch (glob)
   */mercurial/dispatch.py:* in _callcatch (glob)
   */mercurial/scmutil.py:* in callcatch (glob)
   */mercurial/dispatch.py:* in _runcatchfunc (glob)
   */mercurial/dispatch.py:* in _dispatch (glob)
   */mercurial/dispatch.py:* in runcommand (glob)
   */mercurial/dispatch.py:* in _runcommand (glob)
   */mercurial/dispatch.py:* in <lambda> (glob)
   */mercurial/util.py:* in check (glob)
   $TESTTMP/buggylocking.py:* in buggylocking (glob)
#endif
#if pyoxidizer
  $ hg buggylocking --traceback
  devel-warn: "wlock" acquired after "lock" at:
   <string>:* (glob)
   mercurial.dispatch:* in run (glob)
   mercurial.dispatch:* in dispatch (glob)
   mercurial.dispatch:* in _rundispatch (glob)
   mercurial.dispatch:* in _runcatch (glob)
   mercurial.dispatch:* in _callcatch (glob)
   mercurial.scmutil:* in callcatch (glob)
   mercurial.dispatch:* in _runcatchfunc (glob)
   mercurial.dispatch:* in _dispatch (glob)
   mercurial.dispatch:* in runcommand (glob)
   mercurial.dispatch:* in _runcommand (glob)
   mercurial.dispatch:* in <lambda> (glob)
   mercurial.util:* in check (glob)
   $TESTTMP/buggylocking.py:* in buggylocking (glob)
#endif
  $ hg properlocking
  $ hg nowaitlocking

Writing without lock

  $ hg no-wlock-write
  devel-warn: write with no wlock: "branch" at: $TESTTMP/buggylocking.py:* (nowlockwrite) (glob)

  $ hg no-lock-write
  devel-warn: write with no lock: "fncache" at: $TESTTMP/buggylocking.py:* (nolockwrite) (glob)

Stripping from a transaction

  $ echo a > a
  $ hg add a
  $ hg commit -m a
  $ hg stripintr 2>&1 | egrep -v '^(\*\*|  )'
  Traceback (most recent call last):
  *ProgrammingError: cannot strip from inside a transaction (glob)

  $ hg oldanddeprecated
  devel-warn: foorbar is deprecated, go shopping
  (compatibility will be dropped after Mercurial-42.1337, update your code.) at: $TESTTMP/buggylocking.py:* (oldanddeprecated) (glob)

#if no-chg no-pyoxidizer
  $ hg oldanddeprecated --traceback
  devel-warn: foorbar is deprecated, go shopping
  (compatibility will be dropped after Mercurial-42.1337, update your code.) at:
   */hg:* in <module> (glob) (?)
   */mercurial/dispatch.py:* in run (glob)
   */mercurial/dispatch.py:* in dispatch (glob)
   */mercurial/dispatch.py:* in _rundispatch (glob)
   */mercurial/dispatch.py:* in _runcatch (glob)
   */mercurial/dispatch.py:* in _callcatch (glob)
   */mercurial/scmutil.py* in callcatch (glob)
   */mercurial/dispatch.py:* in _runcatchfunc (glob)
   */mercurial/dispatch.py:* in _dispatch (glob)
   */mercurial/dispatch.py:* in runcommand (glob)
   */mercurial/dispatch.py:* in _runcommand (glob)
   */mercurial/dispatch.py:* in <lambda> (glob)
   */mercurial/util.py:* in check (glob)
   $TESTTMP/buggylocking.py:* in oldanddeprecated (glob)
#endif
#if chg no-pyoxidizer
  $ hg oldanddeprecated --traceback
  devel-warn: foorbar is deprecated, go shopping
  (compatibility will be dropped after Mercurial-42.1337, update your code.) at:
   */hg:* in <module> (glob)
   */mercurial/dispatch.py:* in run (glob)
   */mercurial/dispatch.py:* in dispatch (glob)
   */mercurial/dispatch.py:* in _rundispatch (glob)
   */mercurial/dispatch.py:* in _runcatch (glob)
   */mercurial/dispatch.py:* in _callcatch (glob)
   */mercurial/scmutil.py:* in callcatch (glob)
   */mercurial/dispatch.py:* in _runcatchfunc (glob)
   */mercurial/dispatch.py:* in _dispatch (glob)
   */mercurial/dispatch.py:* in runcommand (glob)
   */mercurial/dispatch.py:* in _runcommand (glob)
   */mercurial/dispatch.py:* in <lambda> (glob)
   */mercurial/util.py:* in check (glob)
   */mercurial/commands.py:* in serve (glob)
   */mercurial/server.py:* in runservice (glob)
   */mercurial/commandserver.py:* in run (glob)
   */mercurial/commandserver.py:* in _mainloop (glob)
   */mercurial/commandserver.py:* in _acceptnewconnection (glob)
   */mercurial/commandserver.py:* in _runworker (glob)
   */mercurial/commandserver.py:* in _serverequest (glob)
   */mercurial/commandserver.py:* in serve (glob)
   */mercurial/commandserver.py:* in serveone (glob)
   */mercurial/chgserver.py:* in runcommand (glob)
   */mercurial/commandserver.py:* in runcommand (glob)
   */mercurial/commandserver.py:* in _dispatchcommand (glob)
   */mercurial/dispatch.py:* in dispatch (glob)
   */mercurial/dispatch.py:* in _rundispatch (glob)
   */mercurial/dispatch.py:* in _runcatch (glob)
   */mercurial/dispatch.py:* in _callcatch (glob)
   */mercurial/scmutil.py:* in callcatch (glob)
   */mercurial/dispatch.py:* in _runcatchfunc (glob)
   */mercurial/dispatch.py:* in _dispatch (glob)
   */mercurial/dispatch.py:* in runcommand (glob)
   */mercurial/dispatch.py:* in _runcommand (glob)
   */mercurial/dispatch.py:* in <lambda> (glob)
   */mercurial/util.py:* in check (glob)
   $TESTTMP/buggylocking.py:* in oldanddeprecated (glob)
#endif
#if pyoxidizer
  $ hg oldanddeprecated --traceback
  devel-warn: foorbar is deprecated, go shopping
  (compatibility will be dropped after Mercurial-42.1337, update your code.) at:
   <string>:* (glob)
   mercurial.dispatch:* in run (glob)
   mercurial.dispatch:* in dispatch (glob)
   mercurial.dispatch:* in _rundispatch (glob)
   mercurial.dispatch:* in _runcatch (glob)
   mercurial.dispatch:* in _callcatch (glob)
   mercurial.scmutil:* in callcatch (glob)
   mercurial.dispatch:* in _runcatchfunc (glob)
   mercurial.dispatch:* in _dispatch (glob)
   mercurial.dispatch:* in runcommand (glob)
   mercurial.dispatch:* in _runcommand (glob)
   mercurial.dispatch:* in <lambda> (glob)
   mercurial.util:* in check (glob)
   $TESTTMP/buggylocking.py:* in oldanddeprecated (glob)
#endif

#if no-chg no-pyoxidizer
  $ hg blackbox -l 7
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> devel-warn: foorbar is deprecated, go shopping
  (compatibility will be dropped after Mercurial-42.1337, update your code.) at: $TESTTMP/buggylocking.py:* (oldanddeprecated) (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated exited 0 after * seconds (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated --traceback
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> devel-warn: foorbar is deprecated, go shopping
  (compatibility will be dropped after Mercurial-42.1337, update your code.) at:
   */hg:* in <module> (glob) (?)
   */mercurial/dispatch.py:* in run (glob)
   */mercurial/dispatch.py:* in dispatch (glob)
   */mercurial/dispatch.py:* in _rundispatch (glob)
   */mercurial/dispatch.py:* in _runcatch (glob)
   */mercurial/dispatch.py:* in _callcatch (glob)
   */mercurial/scmutil.py* in callcatch (glob)
   */mercurial/dispatch.py:* in _runcatchfunc (glob)
   */mercurial/dispatch.py:* in _dispatch (glob)
   */mercurial/dispatch.py:* in runcommand (glob)
   */mercurial/dispatch.py:* in _runcommand (glob)
   */mercurial/dispatch.py:* in <lambda> (glob)
   */mercurial/util.py:* in check (glob)
   $TESTTMP/buggylocking.py:* in oldanddeprecated (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated --traceback exited 0 after * seconds (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> blackbox -l 7
#endif
#if chg no-pyoxidizer
  $ hg blackbox -l 7
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> devel-warn: foorbar is deprecated, go shopping
  (compatibility will be dropped after Mercurial-42.1337, update your code.) at: $TESTTMP/buggylocking.py:* (oldanddeprecated) (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated exited 0 after * seconds (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated --traceback
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> devel-warn: foorbar is deprecated, go shopping
  (compatibility will be dropped after Mercurial-42.1337, update your code.) at:
   */hg:* in <module> (glob)
   */mercurial/dispatch.py:* in run (glob)
   */mercurial/dispatch.py:* in dispatch (glob)
   */mercurial/dispatch.py:* in _rundispatch (glob)
   */mercurial/dispatch.py:* in _runcatch (glob)
   */mercurial/dispatch.py:* in _callcatch (glob)
   */mercurial/scmutil.py:* in callcatch (glob)
   */mercurial/dispatch.py:* in _runcatchfunc (glob)
   */mercurial/dispatch.py:* in _dispatch (glob)
   */mercurial/dispatch.py:* in runcommand (glob)
   */mercurial/dispatch.py:* in _runcommand (glob)
   */mercurial/dispatch.py:* in <lambda> (glob)
   */mercurial/util.py:* in check (glob)
   */mercurial/commands.py:* in serve (glob)
   */mercurial/server.py:* in runservice (glob)
   */mercurial/commandserver.py:* in run (glob)
   */mercurial/commandserver.py:* in _mainloop (glob)
   */mercurial/commandserver.py:* in _acceptnewconnection (glob)
   */mercurial/commandserver.py:* in _runworker (glob)
   */mercurial/commandserver.py:* in _serverequest (glob)
   */mercurial/commandserver.py:* in serve (glob)
   */mercurial/commandserver.py:* in serveone (glob)
   */mercurial/chgserver.py:* in runcommand (glob)
   */mercurial/commandserver.py:* in runcommand (glob)
   */mercurial/commandserver.py:* in _dispatchcommand (glob)
   */mercurial/dispatch.py:* in dispatch (glob)
   */mercurial/dispatch.py:* in _rundispatch (glob)
   */mercurial/dispatch.py:* in _runcatch (glob)
   */mercurial/dispatch.py:* in _callcatch (glob)
   */mercurial/scmutil.py:* in callcatch (glob)
   */mercurial/dispatch.py:* in _runcatchfunc (glob)
   */mercurial/dispatch.py:* in _dispatch (glob)
   */mercurial/dispatch.py:* in runcommand (glob)
   */mercurial/dispatch.py:* in _runcommand (glob)
   */mercurial/dispatch.py:* in <lambda> (glob)
   */mercurial/util.py:* in check (glob)
   $TESTTMP/buggylocking.py:* in oldanddeprecated (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated --traceback exited 0 after * seconds (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> blackbox -l 7
#endif
#if pyoxidizer
  $ hg blackbox -l 7
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> devel-warn: foorbar is deprecated, go shopping
  (compatibility will be dropped after Mercurial-42.1337, update your code.) at: $TESTTMP/buggylocking.py:* (oldanddeprecated) (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated exited 0 after * seconds (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated --traceback
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> devel-warn: foorbar is deprecated, go shopping
  (compatibility will be dropped after Mercurial-42.1337, update your code.) at:
   <string>:* in <module> (glob)
   mercurial.dispatch:* in run (glob)
   mercurial.dispatch:* in dispatch (glob)
   mercurial.dispatch:* in _rundispatch (glob)
   mercurial.dispatch:* in _runcatch (glob)
   mercurial.dispatch:* in _callcatch (glob)
   mercurial.scmutil* in callcatch (glob)
   mercurial.dispatch:* in _runcatchfunc (glob)
   mercurial.dispatch:* in _dispatch (glob)
   mercurial.dispatch:* in runcommand (glob)
   mercurial.dispatch:* in _runcommand (glob)
   mercurial.dispatch:* in <lambda> (glob)
   mercurial.util:* in check (glob)
   $TESTTMP/buggylocking.py:* in oldanddeprecated (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated --traceback exited 0 after * seconds (glob)
  1970-01-01 00:00:00.000 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> blackbox -l 7
#endif

Test programming error failure:

  $ hg buggytransaction 2>&1 | egrep -v '^  '
  ** Unknown exception encountered with possibly-broken third-party extension "buggylocking" (version N/A)
  ** which supports versions unknown of Mercurial.
  ** Please disable "buggylocking" and try your action again.
  ** If that fixes the bug please report it to the extension author.
  ** Python * (glob)
  ** Mercurial Distributed SCM (*) (glob)
  ** Extensions loaded: * (glob)
  ** ProgrammingError: transaction requires locking
  Traceback (most recent call last):
  *ProgrammingError: transaction requires locking (glob)

  $ hg programmingerror 2>&1 | egrep -v '^  '
  ** Unknown exception encountered with possibly-broken third-party extension "buggylocking" (version N/A)
  ** which supports versions unknown of Mercurial.
  ** Please disable "buggylocking" and try your action again.
  ** If that fixes the bug please report it to the extension author.
  ** Python * (glob)
  ** Mercurial Distributed SCM (*) (glob)
  ** Extensions loaded: * (glob)
  ** ProgrammingError: something went wrong
  ** (try again)
  Traceback (most recent call last):
  *ProgrammingError: something went wrong (glob)

Old style deprecation warning

  $ hg nouiwarning
  $TESTTMP/buggylocking.py:*: DeprecationWarning: this is a test (glob)
  (compatibility will be dropped after Mercurial-13.37, update your code.)
    util.nouideprecwarn(b'this is a test', b'13.37')

(disabled outside of test run)

  $ HGEMITWARNINGS= hg nouiwarning

Test warning on config option access and registration

  $ cat << EOF > ${TESTTMP}/buggyconfig.py
  > """A small extension that tests our developer warnings for config"""
  > 
  > from mercurial import configitems, registrar
  > 
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > 
  > configtable = {}
  > configitem = registrar.configitem(configtable)
  > 
  > configitem(b'test', b'some', default=b'foo')
  > configitem(b'test', b'dynamic', default=configitems.dynamicdefault)
  > configitem(b'test', b'callable', default=list)
  > # overwrite a core config
  > configitem(b'ui', b'quiet', default=False)
  > configitem(b'ui', b'interactive', default=None)
  > 
  > @command(b'buggyconfig')
  > def cmdbuggyconfig(ui, repo):
  >     repo.ui.config(b'ui', b'quiet', True)
  >     repo.ui.config(b'ui', b'interactive', False)
  >     repo.ui.config(b'test', b'some', b'bar')
  >     repo.ui.config(b'test', b'some', b'foo')
  >     repo.ui.config(b'test', b'dynamic', b'some-required-default')
  >     repo.ui.config(b'test', b'dynamic')
  >     repo.ui.config(b'test', b'callable', [])
  >     repo.ui.config(b'test', b'callable', b'foo')
  >     repo.ui.config(b'test', b'unregistered')
  >     repo.ui.config(b'unregistered', b'unregistered')
  > EOF

  $ hg --config "extensions.buggyconfig=${TESTTMP}/buggyconfig.py" buggyconfig
  devel-warn: extension 'buggyconfig' overwrite config item 'ui.interactive' at: */mercurial/extensions.py:* (_loadextra) (glob) (no-pyoxidizer !)
  devel-warn: extension 'buggyconfig' overwrite config item 'ui.quiet' at: */mercurial/extensions.py:* (_loadextra) (glob) (no-pyoxidizer !)
  devel-warn: extension 'buggyconfig' overwrite config item 'ui.interactive' at: mercurial.extensions:* (_loadextra) (glob) (pyoxidizer !)
  devel-warn: extension 'buggyconfig' overwrite config item 'ui.quiet' at: mercurial.extensions:* (_loadextra) (glob) (pyoxidizer !)
  devel-warn: specifying a mismatched default value for a registered config item: 'ui.quiet' 'True' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
  devel-warn: specifying a mismatched default value for a registered config item: 'ui.interactive' 'False' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
  devel-warn: specifying a mismatched default value for a registered config item: 'test.some' 'bar' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
  devel-warn: config item requires an explicit default value: 'test.dynamic' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
  devel-warn: specifying a mismatched default value for a registered config item: 'test.callable' 'foo' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
  devel-warn: accessing unregistered config item: 'test.unregistered' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
  devel-warn: accessing unregistered config item: 'unregistered.unregistered' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)

  $ cd ..