view tests/test-bad-extension.t @ 33289:abd7dedbaa36

sparse: vendor Facebook-developed extension

Facebook has developed an extension to enable "sparse" checkouts -
a working directory with a subset of files. This feature is a critical
component in enabling repositories to scale to infinite number of
files while retaining reasonable performance. It's worth noting
that sparse checkout is only one possible solution to this problem:
another is virtual filesystems that realize files on first access.
But given that virtual filesystems may not be accessible to all
users, sparse checkout is necessary as a fallback.

Per mailing list discussion at
https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-March/095868.html
we want to add sparse checkout to the Mercurial distribution via
roughly the following mechanism:

1. Vendor extension as-is with minimal modifications (this patch)
2. Refactor extension so it is more clearly experimental and inline
   with Mercurial practices
3. Move code from extension into core where possible
4. Drop experimental labeling and/or move feature into core
   after sign-off from narrow clone feature owners

This commit essentially copies the sparse extension and tests
from revision 71e0a2aeca92a4078fe1b8c76e32c88ff1929737 of the
https://bitbucket.org/facebook/hg-experimental repository.

A list of modifications made as part of vendoring is as follows:

* "EXPERIMENTAL" added to module docstring
* Imports were changed to match Mercurial style conventions
* "testedwith" value was updated to core Mercurial special value and
  comment boilerplate was inserted
* A "clone_sparse" function was renamed to "clonesparse" to appease
  the style checker
* Paths to the sparse extension in tests reflect built-in location
* test-sparse-extensions.t was renamed to test-sparse-fsmonitor.t
  and references to "simplecache" were removed. The test always skips
  because it isn't trivial to run it given the way we currently run
  fsmonitor tests
* A double empty line was removed from test-sparse-profiles.t

There are aspects of the added code that are obviously not ideal.
The goal is to make a minimal number of modifications as part of
the vendoring to make it easier to track changes from the original
implementation. Refactoring will occur in subsequent patches.

ensure that failing ui.atexit handlers report sensibly

  $ cat > $TESTTMP/bailatexit.py <<EOF
  > from mercurial import util
  > def bail():
  >     raise RuntimeError('ui.atexit handler exception')
  > 
  > def extsetup(ui):
  >     ui.atexit(bail)
  > EOF
  $ hg -q --config extensions.bailatexit=$TESTTMP/bailatexit.py \
  >  help help
  hg help [-ecks] [TOPIC]
  
  show help for a given topic or a help overview
  error in exit handlers:
  Traceback (most recent call last):
    File "*/mercurial/dispatch.py", line *, in _runexithandlers (glob)
      func(*args, **kwargs)
    File "$TESTTMP/bailatexit.py", line *, in bail (glob)
      raise RuntimeError('ui.atexit handler exception')
  RuntimeError: ui.atexit handler exception
  [255]

  $ rm $TESTTMP/bailatexit.py

another bad extension

  $ 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 commands, extensions, registrar
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > @command(b'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
  could not import hgext.badext2 (No module named *badext2): trying hgext3rd.badext2 (glob)
  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