$ echo 'raise Exception("bit bucket overflow")' > badext.py

  $ abspathexc=`pwd`/badext.py

  $ cat >baddocext.py <<EOF

  > """

  > baddocext is bad

  > """

  > EOF

  $ abspathdoc=`pwd`/baddocext.py

  $ cat <<EOF >> $HGRCPATH

  > [extensions]

  > gpg =

  > hgext.gpg =

  > badext = $abspathexc

  > baddocext = $abspathdoc

  > badext2 =

  > EOF

  $ hg -q help help 2>&1 |grep extension

  *** failed to import extension badext from $TESTTMP/badext.py: bit bucket overflow

  *** failed to import extension badext2: No module named badext2

show traceback

  $ hg -q help help --traceback 2>&1 | egrep ' extension|^Exception|Traceback|ImportError'

  *** failed to import extension badext from $TESTTMP/badext.py: bit bucket overflow

  Traceback (most recent call last):

  Exception: bit bucket overflow

  *** failed to import extension badext2: No module named badext2

  Traceback (most recent call last):

  ImportError: No module named badext2

names of extensions failed to load can be accessed via extensions.notloaded()

  $ cat <<EOF > showbadexts.py

  > from mercurial import cmdutil, commands, extensions

  > cmdtable = {}

  > command = cmdutil.command(cmdtable)

  > @command('showbadexts', norepo=True)

  > def showbadexts(ui, *pats, **opts):

  >     ui.write('BADEXTS: %s\n' % ' '.join(sorted(extensions.notloaded())))

  > EOF

  $ hg --config extensions.badexts=showbadexts.py showbadexts 2>&1 | grep '^BADEXTS'

  BADEXTS: badext badext2

show traceback for ImportError of hgext.name if debug is set

(note that --debug option isn't applied yet when loading extensions)

  $ (hg -q help help --traceback --config ui.debug=True 2>&1) \

  > | grep -v '^ ' \

  > | egrep 'extension..[^p]|^Exception|Traceback|ImportError|not import'

  *** failed to import extension badext from $TESTTMP/badext.py: bit bucket overflow

  Traceback (most recent call last):

  Exception: bit bucket overflow

  Traceback (most recent call last):

  ImportError: No module named *badext2 (glob)

  could not import hgext3rd.badext2 (No module named *badext2): trying badext2 (glob)

  Traceback (most recent call last):

  ImportError: No module named *badext2 (glob)

  *** failed to import extension badext2: No module named badext2

  Traceback (most recent call last):

  ImportError: No module named badext2

confirm that there's no crash when an extension's documentation is bad

  $ hg help --keyword baddocext

  *** failed to import extension badext from $TESTTMP/badext.py: bit bucket overflow

  *** failed to import extension badext2: No module named badext2

  Topics:

   extensions Using Additional Features