extensions: clear aftercallbacks after execution (issue4646)

It was reported that enabling pager without color could cause a hang.
Inserting print statements revealed that the callbacks in
extensions._aftercallbacks were being invoked twice.

extensions.loadall can be called multiple times. If entries in
extensions._aftercallbacks linger between calls, this could result
in double execution of the callbacks. This can lead to unwanted
behavior.

The reproduce steps in the bug seem to only occur when the output of
a command is less than the size of the current screen. This is not
something that can easily be tested. I verified the test case works
with this patch and that pager and color interaction continues to
work. Since we have no existing automated tests for pager, this sadly
appears to be the best testing I can do.

mercurial/extensions.py

@@ -1,439 +1,443
 # extensions.py - extension handling for mercurial
 #
 # Copyright 2005-2007 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 import imp, os
 import util, cmdutil, error
 from i18n import _, gettext
 
 _extensions = {}
 _aftercallbacks = {}
 _order = []
 _ignore = ['hbisect', 'bookmarks', 'parentrevspec', 'interhg', 'inotify']
 
 def extensions(ui=None):
     if ui:
         def enabled(name):
             for format in ['%s', 'hgext.%s']:
                 conf = ui.config('extensions', format % name)
                 if conf is not None and not conf.startswith('!'):
                     return True
     else:
         enabled = lambda name: True
     for name in _order:
         module = _extensions[name]
         if module and enabled(name):
             yield name, module
 
 def find(name):
     '''return module with given extension name'''
     mod = None
     try:
         mod =  _extensions[name]
     except KeyError:
         for k, v in _extensions.iteritems():
             if k.endswith('.' + name) or k.endswith('/' + name):
                 mod = v
                 break
     if not mod:
         raise KeyError(name)
     return mod
 
 def loadpath(path, module_name):
     module_name = module_name.replace('.', '_')
     path = util.normpath(util.expandpath(path))
     if os.path.isdir(path):
         # module/__init__.py style
         d, f = os.path.split(path)
         fd, fpath, desc = imp.find_module(f, [d])
         return imp.load_module(module_name, fd, fpath, desc)
     else:
         try:
             return imp.load_source(module_name, path)
         except IOError, exc:
             if not exc.filename:
                 exc.filename = path # python does not fill this
             raise
 
 def load(ui, name, path):
     if name.startswith('hgext.') or name.startswith('hgext/'):
         shortname = name[6:]
     else:
         shortname = name
     if shortname in _ignore:
         return None
     if shortname in _extensions:
         return _extensions[shortname]
     _extensions[shortname] = None
     if path:
         # the module will be loaded in sys.modules
         # choose an unique name so that it doesn't
         # conflicts with other modules
         mod = loadpath(path, 'hgext.%s' % name)
     else:
         def importh(name):
             mod = __import__(name)
             components = name.split('.')
             for comp in components[1:]:
                 mod = getattr(mod, comp)
             return mod
         try:
             mod = importh("hgext.%s" % name)
         except ImportError, err:
             ui.debug('could not import hgext.%s (%s): trying %s\n'
                      % (name, err, name))
             mod = importh(name)
     _extensions[shortname] = mod
     _order.append(shortname)
     for fn in _aftercallbacks.get(shortname, []):
         fn(loaded=True)
     return mod
 
 def loadall(ui):
     result = ui.configitems("extensions")
     newindex = len(_order)
     for (name, path) in result:
         if path:
             if path[0] == '!':
                 continue
         try:
             load(ui, name, path)
         except KeyboardInterrupt:
             raise
         except Exception, inst:
             if path:
                 ui.warn(_("*** failed to import extension %s from %s: %s\n")
                         % (name, path, inst))
             else:
                 ui.warn(_("*** failed to import extension %s: %s\n")
                         % (name, inst))
 
     for name in _order[newindex:]:
         uisetup = getattr(_extensions[name], 'uisetup', None)
         if uisetup:
             uisetup(ui)
 
     for name in _order[newindex:]:
         extsetup = getattr(_extensions[name], 'extsetup', None)
         if extsetup:
             try:
                 extsetup(ui)
             except TypeError:
                 if extsetup.func_code.co_argcount != 0:
                     raise
                 extsetup() # old extsetup with no ui argument
 
     # Call aftercallbacks that were never met.
     for shortname in _aftercallbacks:
         if shortname in _extensions:
             continue
 
         for fn in _aftercallbacks[shortname]:
             fn(loaded=False)
 
+    # loadall() is called multiple times and lingering _aftercallbacks
+    # entries could result in double execution. See issue4646.
+    _aftercallbacks.clear()
+
 def afterloaded(extension, callback):
     '''Run the specified function after a named extension is loaded.
 
     If the named extension is already loaded, the callback will be called
     immediately.
 
     If the named extension never loads, the callback will be called after
     all extensions have been loaded.
 
     The callback receives the named argument ``loaded``, which is a boolean
     indicating whether the dependent extension actually loaded.
     '''
 
     if extension in _extensions:
         callback(loaded=True)
     else:
         _aftercallbacks.setdefault(extension, []).append(callback)
 
 def bind(func, *args):
     '''Partial function application
 
       Returns a new function that is the partial application of args and kwargs
       to func.  For example,
 
           f(1, 2, bar=3) === bind(f, 1)(2, bar=3)'''
     assert callable(func)
     def closure(*a, **kw):
         return func(*(args + a), **kw)
     return closure
 
 def wrapcommand(table, command, wrapper, synopsis=None, docstring=None):
     '''Wrap the command named `command' in table
 
     Replace command in the command table with wrapper. The wrapped command will
     be inserted into the command table specified by the table argument.
 
     The wrapper will be called like
 
       wrapper(orig, *args, **kwargs)
 
     where orig is the original (wrapped) function, and *args, **kwargs
     are the arguments passed to it.
 
     Optionally append to the command synopsis and docstring, used for help.
     For example, if your extension wraps the ``bookmarks`` command to add the
     flags ``--remote`` and ``--all`` you might call this function like so:
 
       synopsis = ' [-a] [--remote]'
       docstring = """
 
       The ``remotenames`` extension adds the ``--remote`` and ``--all`` (``-a``)
       flags to the bookmarks command. Either flag will show the remote bookmarks
       known to the repository; ``--remote`` will also supress the output of the
       local bookmarks.
       """
 
       extensions.wrapcommand(commands.table, 'bookmarks', exbookmarks,
                              synopsis, docstring)
     '''
     assert callable(wrapper)
     aliases, entry = cmdutil.findcmd(command, table)
     for alias, e in table.iteritems():
         if e is entry:
             key = alias
             break
 
     origfn = entry[0]
     wrap = bind(util.checksignature(wrapper), util.checksignature(origfn))
 
     wrap.__module__ = getattr(origfn, '__module__')
 
     doc = getattr(origfn, '__doc__')
     if docstring is not None:
         doc += docstring
     wrap.__doc__ = doc
 
     newentry = list(entry)
     newentry[0] = wrap
     if synopsis is not None:
         newentry[2] += synopsis
     table[key] = tuple(newentry)
     return entry
 
 def wrapfunction(container, funcname, wrapper):
     '''Wrap the function named funcname in container
 
     Replace the funcname member in the given container with the specified
     wrapper. The container is typically a module, class, or instance.
 
     The wrapper will be called like
 
       wrapper(orig, *args, **kwargs)
 
     where orig is the original (wrapped) function, and *args, **kwargs
     are the arguments passed to it.
 
     Wrapping methods of the repository object is not recommended since
     it conflicts with extensions that extend the repository by
     subclassing. All extensions that need to extend methods of
     localrepository should use this subclassing trick: namely,
     reposetup() should look like
 
       def reposetup(ui, repo):
           class myrepo(repo.__class__):
               def whatever(self, *args, **kwargs):
                   [...extension stuff...]
                   super(myrepo, self).whatever(*args, **kwargs)
                   [...extension stuff...]
 
           repo.__class__ = myrepo
 
     In general, combining wrapfunction() with subclassing does not
     work. Since you cannot control what other extensions are loaded by
     your end users, you should play nicely with others by using the
     subclass trick.
     '''
     assert callable(wrapper)
 
     origfn = getattr(container, funcname)
     assert callable(origfn)
     setattr(container, funcname, bind(wrapper, origfn))
     return origfn
 
 def _disabledpaths(strip_init=False):
     '''find paths of disabled extensions. returns a dict of {name: path}
     removes /__init__.py from packages if strip_init is True'''
     import hgext
     extpath = os.path.dirname(os.path.abspath(hgext.__file__))
     try: # might not be a filesystem path
         files = os.listdir(extpath)
     except OSError:
         return {}
 
     exts = {}
     for e in files:
         if e.endswith('.py'):
             name = e.rsplit('.', 1)[0]
             path = os.path.join(extpath, e)
         else:
             name = e
             path = os.path.join(extpath, e, '__init__.py')
             if not os.path.exists(path):
                 continue
             if strip_init:
                 path = os.path.dirname(path)
         if name in exts or name in _order or name == '__init__':
             continue
         exts[name] = path
     return exts
 
 def _moduledoc(file):
     '''return the top-level python documentation for the given file
 
     Loosely inspired by pydoc.source_synopsis(), but rewritten to
     handle triple quotes and to return the whole text instead of just
     the synopsis'''
     result = []
 
     line = file.readline()
     while line[:1] == '#' or not line.strip():
         line = file.readline()
         if not line:
             break
 
     start = line[:3]
     if start == '"""' or start == "'''":
         line = line[3:]
         while line:
             if line.rstrip().endswith(start):
                 line = line.split(start)[0]
                 if line:
                     result.append(line)
                 break
             elif not line:
                 return None # unmatched delimiter
             result.append(line)
             line = file.readline()
     else:
         return None
 
     return ''.join(result)
 
 def _disabledhelp(path):
     '''retrieve help synopsis of a disabled extension (without importing)'''
     try:
         file = open(path)
     except IOError:
         return
     else:
         doc = _moduledoc(file)
         file.close()
 
     if doc: # extracting localized synopsis
         return gettext(doc).splitlines()[0]
     else:
         return _('(no help text available)')
 
 def disabled():
     '''find disabled extensions from hgext. returns a dict of {name: desc}'''
     try:
         from hgext import __index__
         return dict((name, gettext(desc))
                     for name, desc in __index__.docs.iteritems()
                     if name not in _order)
     except (ImportError, AttributeError):
         pass
 
     paths = _disabledpaths()
     if not paths:
         return {}
 
     exts = {}
     for name, path in paths.iteritems():
         doc = _disabledhelp(path)
         if doc:
             exts[name] = doc
 
     return exts
 
 def disabledext(name):
     '''find a specific disabled extension from hgext. returns desc'''
     try:
         from hgext import __index__
         if name in _order:  # enabled
             return
         else:
             return gettext(__index__.docs.get(name))
     except (ImportError, AttributeError):
         pass
 
     paths = _disabledpaths()
     if name in paths:
         return _disabledhelp(paths[name])
 
 def disabledcmd(ui, cmd, strict=False):
     '''import disabled extensions until cmd is found.
     returns (cmdname, extname, module)'''
 
     paths = _disabledpaths(strip_init=True)
     if not paths:
         raise error.UnknownCommand(cmd)
 
     def findcmd(cmd, name, path):
         try:
             mod = loadpath(path, 'hgext.%s' % name)
         except Exception:
             return
         try:
             aliases, entry = cmdutil.findcmd(cmd,
                 getattr(mod, 'cmdtable', {}), strict)
         except (error.AmbiguousCommand, error.UnknownCommand):
             return
         except Exception:
             ui.warn(_('warning: error finding commands in %s\n') % path)
             ui.traceback()
             return
         for c in aliases:
             if c.startswith(cmd):
                 cmd = c
                 break
         else:
             cmd = aliases[0]
         return (cmd, name, mod)
 
     ext = None
     # first, search for an extension with the same name as the command
     path = paths.pop(cmd, None)
     if path:
         ext = findcmd(cmd, cmd, path)
     if not ext:
         # otherwise, interrogate each extension until there's a match
         for name, path in paths.iteritems():
             ext = findcmd(cmd, name, path)
             if ext:
                 break
     if ext and 'DEPRECATED' not in ext.__doc__:
         return ext
 
     raise error.UnknownCommand(cmd)
 
 def enabled(shortname=True):
     '''return a dict of {name: desc} of extensions'''
     exts = {}
     for ename, ext in extensions():
         doc = (gettext(ext.__doc__) or _('(no help text available)'))
         if shortname:
             ename = ename.split('.')[-1]
         exts[ename] = doc.splitlines()[0].strip()
 
     return exts
 
 def moduleversion(module):
     '''return version information from given module as a string'''
     if (util.safehasattr(module, 'getversion')
           and callable(module.getversion)):
         version = module.getversion()
     elif util.safehasattr(module, '__version__'):
         version = module.__version__
     else:
         version = ''
     if isinstance(version, (list, tuple)):
         version = '.'.join(str(o) for o in version)
     return version