extensions: gracefully warn when doing min version check with no local version

After doing a `make clean`, I started getting cryptic failures to import
extensions with the `minimumhgversion` attribute on py3:

    *** failed to import extension evolve: '>' not supported between instances of 'int' and 'NoneType'
    *** failed to import extension topic: '>' not supported between instances of 'int' and 'NoneType'

This now handles the `(None, None)` tuple before comparing, and disables the
extension with the same friendly message as in py2.

Differential Revision: https://phab.mercurial-scm.org/D9363

mercurial/extensions.py

@@ -1,941 +1,944 b''
 # 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.
 
 from __future__ import absolute_import
 
 import ast
 import collections
 import functools
 import imp
 import inspect
 import os
 
 from .i18n import (
     _,
     gettext,
 )
 from .pycompat import (
     getattr,
     open,
     setattr,
 )
 
 from . import (
     cmdutil,
     configitems,
     error,
     pycompat,
     util,
 )
 
 from .utils import stringutil
 
 _extensions = {}
 _disabledextensions = {}
 _aftercallbacks = {}
 _order = []
 _builtin = {
     b'hbisect',
     b'bookmarks',
     b'color',
     b'parentrevspec',
     b'progress',
     b'interhg',
     b'inotify',
     b'hgcia',
     b'shelve',
 }
 
 
 def extensions(ui=None):
     if ui:
 
         def enabled(name):
             for format in [b'%s', b'hgext.%s']:
                 conf = ui.config(b'extensions', format % name)
                 if conf is not None and not conf.startswith(b'!'):
                     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 pycompat.iteritems(_extensions):
             if k.endswith(b'.' + name) or k.endswith(b'/' + name):
                 mod = v
                 break
     if not mod:
         raise KeyError(name)
     return mod
 
 
 def loadpath(path, module_name):
     module_name = module_name.replace(b'.', b'_')
     path = util.normpath(util.expandpath(path))
     module_name = pycompat.fsdecode(module_name)
     path = pycompat.fsdecode(path)
     if os.path.isdir(path):
         # module/__init__.py style
         d, f = os.path.split(path)
         fd, fpath, desc = imp.find_module(f, [d])
         # When https://github.com/python/typeshed/issues/3466 is fixed
         # and in a pytype release we can drop this disable.
         return imp.load_module(
             module_name, fd, fpath, desc  # pytype: disable=wrong-arg-types
         )
     else:
         try:
             return imp.load_source(module_name, path)
         except IOError as exc:
             if not exc.filename:
                 exc.filename = path  # python does not fill this
             raise
 
 
 def _importh(name):
     """import and return the <name> module"""
     mod = __import__(pycompat.sysstr(name))
     components = name.split(b'.')
     for comp in components[1:]:
         mod = getattr(mod, comp)
     return mod
 
 
 def _importext(name, path=None, reportfunc=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, b'hgext.%s' % name)
     else:
         try:
             mod = _importh(b"hgext.%s" % name)
         except ImportError as err:
             if reportfunc:
                 reportfunc(err, b"hgext.%s" % name, b"hgext3rd.%s" % name)
             try:
                 mod = _importh(b"hgext3rd.%s" % name)
             except ImportError as err:
                 if reportfunc:
                     reportfunc(err, b"hgext3rd.%s" % name, name)
                 mod = _importh(name)
     return mod
 
 
 def _reportimporterror(ui, err, failed, next):
     # note: this ui.log happens before --debug is processed,
     #       Use --config ui.debug=1 to see them.
     ui.log(
         b'extension',
         b'    - could not import %s (%s): trying %s\n',
         failed,
         stringutil.forcebytestr(err),
         next,
     )
     if ui.debugflag and ui.configbool(b'devel', b'debug.extensions'):
         ui.traceback()
 
 
 def _rejectunicode(name, xs):
     if isinstance(xs, (list, set, tuple)):
         for x in xs:
             _rejectunicode(name, x)
     elif isinstance(xs, dict):
         for k, v in xs.items():
             _rejectunicode(name, k)
             _rejectunicode(b'%s.%s' % (name, stringutil.forcebytestr(k)), v)
     elif isinstance(xs, type(u'')):
         raise error.ProgrammingError(
             b"unicode %r found in %s" % (xs, name),
             hint=b"use b'' to make it byte string",
         )
 
 
 # attributes set by registrar.command
 _cmdfuncattrs = (b'norepo', b'optionalrepo', b'inferrepo')
 
 
 def _validatecmdtable(ui, cmdtable):
     """Check if extension commands have required attributes"""
     for c, e in pycompat.iteritems(cmdtable):
         f = e[0]
         missing = [a for a in _cmdfuncattrs if not util.safehasattr(f, a)]
         if not missing:
             continue
         raise error.ProgrammingError(
             b'missing attributes: %s' % b', '.join(missing),
             hint=b"use @command decorator to register '%s'" % c,
         )
 
 
 def _validatetables(ui, mod):
     """Sanity check for loadable tables provided by extension module"""
     for t in [b'cmdtable', b'colortable', b'configtable']:
         _rejectunicode(t, getattr(mod, t, {}))
     for t in [
         b'filesetpredicate',
         b'internalmerge',
         b'revsetpredicate',
         b'templatefilter',
         b'templatefunc',
         b'templatekeyword',
     ]:
         o = getattr(mod, t, None)
         if o:
             _rejectunicode(t, o._table)
     _validatecmdtable(ui, getattr(mod, 'cmdtable', {}))
 
 
 def load(ui, name, path, loadingtime=None):
     if name.startswith(b'hgext.') or name.startswith(b'hgext/'):
         shortname = name[6:]
     else:
         shortname = name
     if shortname in _builtin:
         return None
     if shortname in _extensions:
         return _extensions[shortname]
     ui.log(b'extension', b'  - loading extension: %s\n', shortname)
     _extensions[shortname] = None
     with util.timedcm('load extension %s', shortname) as stats:
         mod = _importext(name, path, bind(_reportimporterror, ui))
     ui.log(b'extension', b'  > %s extension loaded in %s\n', shortname, stats)
     if loadingtime is not None:
         loadingtime[shortname] += stats.elapsed
 
     # Before we do anything with the extension, check against minimum stated
     # compatibility. This gives extension authors a mechanism to have their
     # extensions short circuit when loaded with a known incompatible version
     # of Mercurial.
     minver = getattr(mod, 'minimumhgversion', None)
-    if minver and util.versiontuple(minver, 2) > util.versiontuple(n=2):
-        msg = _(
-            b'(third party extension %s requires version %s or newer '
-            b'of Mercurial (current: %s); disabling)\n'
-        )
-        ui.warn(msg % (shortname, minver, util.version()))
-        return
+    if minver:
+        curver = util.versiontuple(n=2)
+
+        if None in curver or util.versiontuple(minver, 2) > curver:
+            msg = _(
+                b'(third party extension %s requires version %s or newer '
+                b'of Mercurial (current: %s); disabling)\n'
+            )
+            ui.warn(msg % (shortname, minver, util.version()))
+            return
     ui.log(b'extension', b'    - validating extension tables: %s\n', shortname)
     _validatetables(ui, mod)
 
     _extensions[shortname] = mod
     _order.append(shortname)
     ui.log(
         b'extension', b'    - invoking registered callbacks: %s\n', shortname
     )
     with util.timedcm('callbacks extension %s', shortname) as stats:
         for fn in _aftercallbacks.get(shortname, []):
             fn(loaded=True)
     ui.log(b'extension', b'    > callbacks completed in %s\n', stats)
     return mod
 
 
 def _runuisetup(name, ui):
     uisetup = getattr(_extensions[name], 'uisetup', None)
     if uisetup:
         try:
             uisetup(ui)
         except Exception as inst:
             ui.traceback(force=True)
             msg = stringutil.forcebytestr(inst)
             ui.warn(_(b"*** failed to set up extension %s: %s\n") % (name, msg))
             return False
     return True
 
 
 def _runextsetup(name, ui):
     extsetup = getattr(_extensions[name], 'extsetup', None)
     if extsetup:
         try:
             extsetup(ui)
         except Exception as inst:
             ui.traceback(force=True)
             msg = stringutil.forcebytestr(inst)
             ui.warn(_(b"*** failed to set up extension %s: %s\n") % (name, msg))
             return False
     return True
 
 
 def loadall(ui, whitelist=None):
     loadingtime = collections.defaultdict(int)
     result = ui.configitems(b"extensions")
     if whitelist is not None:
         result = [(k, v) for (k, v) in result if k in whitelist]
     newindex = len(_order)
     ui.log(
         b'extension',
         b'loading %sextensions\n',
         b'additional ' if newindex else b'',
     )
     ui.log(b'extension', b'- processing %d entries\n', len(result))
     with util.timedcm('load all extensions') as stats:
         for (name, path) in result:
             if path:
                 if path[0:1] == b'!':
                     if name not in _disabledextensions:
                         ui.log(
                             b'extension',
                             b'  - skipping disabled extension: %s\n',
                             name,
                         )
                     _disabledextensions[name] = path[1:]
                     continue
             try:
                 load(ui, name, path, loadingtime)
             except Exception as inst:
                 msg = stringutil.forcebytestr(inst)
                 if path:
                     ui.warn(
                         _(b"*** failed to import extension %s from %s: %s\n")
                         % (name, path, msg)
                     )
                 else:
                     ui.warn(
                         _(b"*** failed to import extension %s: %s\n")
                         % (name, msg)
                     )
                 if isinstance(inst, error.Hint) and inst.hint:
                     ui.warn(_(b"*** (%s)\n") % inst.hint)
                 ui.traceback()
 
     ui.log(
         b'extension',
         b'> loaded %d extensions, total time %s\n',
         len(_order) - newindex,
         stats,
     )
     # list of (objname, loadermod, loadername) tuple:
     # - objname is the name of an object in extension module,
     #   from which extra information is loaded
     # - loadermod is the module where loader is placed
     # - loadername is the name of the function,
     #   which takes (ui, extensionname, extraobj) arguments
     #
     # This one is for the list of item that must be run before running any setup
     earlyextraloaders = [
         (b'configtable', configitems, b'loadconfigtable'),
     ]
 
     ui.log(b'extension', b'- loading configtable attributes\n')
     _loadextra(ui, newindex, earlyextraloaders)
 
     broken = set()
     ui.log(b'extension', b'- executing uisetup hooks\n')
     with util.timedcm('all uisetup') as alluisetupstats:
         for name in _order[newindex:]:
             ui.log(b'extension', b'  - running uisetup for %s\n', name)
             with util.timedcm('uisetup %s', name) as stats:
                 if not _runuisetup(name, ui):
                     ui.log(
                         b'extension',
                         b'    - the %s extension uisetup failed\n',
                         name,
                     )
                     broken.add(name)
             ui.log(b'extension', b'  > uisetup for %s took %s\n', name, stats)
             loadingtime[name] += stats.elapsed
     ui.log(b'extension', b'> all uisetup took %s\n', alluisetupstats)
 
     ui.log(b'extension', b'- executing extsetup hooks\n')
     with util.timedcm('all extsetup') as allextetupstats:
         for name in _order[newindex:]:
             if name in broken:
                 continue
             ui.log(b'extension', b'  - running extsetup for %s\n', name)
             with util.timedcm('extsetup %s', name) as stats:
                 if not _runextsetup(name, ui):
                     ui.log(
                         b'extension',
                         b'    - the %s extension extsetup failed\n',
                         name,
                     )
                     broken.add(name)
             ui.log(b'extension', b'  > extsetup for %s took %s\n', name, stats)
             loadingtime[name] += stats.elapsed
     ui.log(b'extension', b'> all extsetup took %s\n', allextetupstats)
 
     for name in broken:
         ui.log(b'extension', b'    - disabling broken %s extension\n', name)
         _extensions[name] = None
 
     # Call aftercallbacks that were never met.
     ui.log(b'extension', b'- executing remaining aftercallbacks\n')
     with util.timedcm('aftercallbacks') as stats:
         for shortname in _aftercallbacks:
             if shortname in _extensions:
                 continue
 
             for fn in _aftercallbacks[shortname]:
                 ui.log(
                     b'extension',
                     b'  - extension %s not loaded, notify callbacks\n',
                     shortname,
                 )
                 fn(loaded=False)
     ui.log(b'extension', b'> remaining aftercallbacks completed in %s\n', stats)
 
     # loadall() is called multiple times and lingering _aftercallbacks
     # entries could result in double execution. See issue4646.
     _aftercallbacks.clear()
 
     # delay importing avoids cyclic dependency (especially commands)
     from . import (
         color,
         commands,
         filemerge,
         fileset,
         revset,
         templatefilters,
         templatefuncs,
         templatekw,
     )
 
     # list of (objname, loadermod, loadername) tuple:
     # - objname is the name of an object in extension module,
     #   from which extra information is loaded
     # - loadermod is the module where loader is placed
     # - loadername is the name of the function,
     #   which takes (ui, extensionname, extraobj) arguments
     ui.log(b'extension', b'- loading extension registration objects\n')
     extraloaders = [
         (b'cmdtable', commands, b'loadcmdtable'),
         (b'colortable', color, b'loadcolortable'),
         (b'filesetpredicate', fileset, b'loadpredicate'),
         (b'internalmerge', filemerge, b'loadinternalmerge'),
         (b'revsetpredicate', revset, b'loadpredicate'),
         (b'templatefilter', templatefilters, b'loadfilter'),
         (b'templatefunc', templatefuncs, b'loadfunction'),
         (b'templatekeyword', templatekw, b'loadkeyword'),
     ]
     with util.timedcm('load registration objects') as stats:
         _loadextra(ui, newindex, extraloaders)
     ui.log(
         b'extension',
         b'> extension registration object loading took %s\n',
         stats,
     )
 
     # Report per extension loading time (except reposetup)
     for name in sorted(loadingtime):
         ui.log(
             b'extension',
             b'> extension %s take a total of %s to load\n',
             name,
             util.timecount(loadingtime[name]),
         )
 
     ui.log(b'extension', b'extension loading complete\n')
 
 
 def _loadextra(ui, newindex, extraloaders):
     for name in _order[newindex:]:
         module = _extensions[name]
         if not module:
             continue  # loading this module failed
 
         for objname, loadermod, loadername in extraloaders:
             extraobj = getattr(module, objname, None)
             if extraobj is not None:
                 getattr(loadermod, loadername)(ui, name, extraobj)
 
 
 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:
         # Report loaded as False if the extension is disabled
         loaded = _extensions[extension] is not None
         callback(loaded=loaded)
     else:
         _aftercallbacks.setdefault(extension, []).append(callback)
 
 
 def populateui(ui):
     """Run extension hooks on the given ui to populate additional members,
     extend the class dynamically, etc.
 
     This will be called after the configuration is loaded, and/or extensions
     are loaded. In general, it's once per ui instance, but in command-server
     and hgweb, this may be called more than once with the same ui.
     """
     for name, mod in extensions(ui):
         hook = getattr(mod, 'uipopulate', None)
         if not hook:
             continue
         try:
             hook(ui)
         except Exception as inst:
             ui.traceback(force=True)
             ui.warn(
                 _(b'*** failed to populate ui by extension %s: %s\n')
                 % (name, stringutil.forcebytestr(inst))
             )
 
 
 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 _updatewrapper(wrap, origfn, unboundwrapper):
     '''Copy and add some useful attributes to wrapper'''
     try:
         wrap.__name__ = origfn.__name__
     except AttributeError:
         pass
     wrap.__module__ = getattr(origfn, '__module__')
     wrap.__doc__ = getattr(origfn, '__doc__')
     wrap.__dict__.update(getattr(origfn, '__dict__', {}))
     wrap._origfunc = origfn
     wrap._unboundwrapper = unboundwrapper
 
 
 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 suppress 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 pycompat.iteritems(table):
         if e is entry:
             key = alias
             break
 
     origfn = entry[0]
     wrap = functools.partial(
         util.checksignature(wrapper), util.checksignature(origfn)
     )
     _updatewrapper(wrap, origfn, wrapper)
     if docstring is not None:
         wrap.__doc__ += docstring
 
     newentry = list(entry)
     newentry[0] = wrap
     if synopsis is not None:
         newentry[2] += synopsis
     table[key] = tuple(newentry)
     return entry
 
 
 def wrapfilecache(cls, propname, wrapper):
     """Wraps a filecache property.
 
     These can't be wrapped using the normal wrapfunction.
     """
     propname = pycompat.sysstr(propname)
     assert callable(wrapper)
     for currcls in cls.__mro__:
         if propname in currcls.__dict__:
             origfn = currcls.__dict__[propname].func
             assert callable(origfn)
 
             def wrap(*args, **kwargs):
                 return wrapper(origfn, *args, **kwargs)
 
             currcls.__dict__[propname].func = wrap
             break
 
     if currcls is object:
         raise AttributeError("type '%s' has no property '%s'" % (cls, propname))
 
 
 class wrappedfunction(object):
     '''context manager for temporarily wrapping a function'''
 
     def __init__(self, container, funcname, wrapper):
         assert callable(wrapper)
         self._container = container
         self._funcname = funcname
         self._wrapper = wrapper
 
     def __enter__(self):
         wrapfunction(self._container, self._funcname, self._wrapper)
 
     def __exit__(self, exctype, excvalue, traceback):
         unwrapfunction(self._container, self._funcname, self._wrapper)
 
 
 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)
     if inspect.ismodule(container):
         # origfn is not an instance or class method. "partial" can be used.
         # "partial" won't insert a frame in traceback.
         wrap = functools.partial(wrapper, origfn)
     else:
         # "partial" cannot be safely used. Emulate its effect by using "bind".
         # The downside is one more frame in traceback.
         wrap = bind(wrapper, origfn)
     _updatewrapper(wrap, origfn, wrapper)
     setattr(container, funcname, wrap)
     return origfn
 
 
 def unwrapfunction(container, funcname, wrapper=None):
     '''undo wrapfunction
 
     If wrappers is None, undo the last wrap. Otherwise removes the wrapper
     from the chain of wrappers.
 
     Return the removed wrapper.
     Raise IndexError if wrapper is None and nothing to unwrap; ValueError if
     wrapper is not None but is not found in the wrapper chain.
     '''
     chain = getwrapperchain(container, funcname)
     origfn = chain.pop()
     if wrapper is None:
         wrapper = chain[0]
     chain.remove(wrapper)
     setattr(container, funcname, origfn)
     for w in reversed(chain):
         wrapfunction(container, funcname, w)
     return wrapper
 
 
 def getwrapperchain(container, funcname):
     '''get a chain of wrappers of a function
 
     Return a list of functions: [newest wrapper, ..., oldest wrapper, origfunc]
 
     The wrapper functions are the ones passed to wrapfunction, whose first
     argument is origfunc.
     '''
     result = []
     fn = getattr(container, funcname)
     while fn:
         assert callable(fn)
         result.append(getattr(fn, '_unboundwrapper', fn))
         fn = getattr(fn, '_origfunc', None)
     return result
 
 
 def _disabledpaths():
     '''find paths of disabled extensions. returns a dict of {name: path}'''
     import hgext
 
     # The hgext might not have a __file__ attribute (e.g. in PyOxidizer) and
     # it might not be on a filesystem even if it does.
     if util.safehasattr(hgext, '__file__'):
         extpath = os.path.dirname(
             os.path.abspath(pycompat.fsencode(hgext.__file__))
         )
         try:
             files = os.listdir(extpath)
         except OSError:
             return {}
     else:
         return {}
 
     exts = {}
     for e in files:
         if e.endswith(b'.py'):
             name = e.rsplit(b'.', 1)[0]
             path = os.path.join(extpath, e)
         else:
             name = e
             path = os.path.join(extpath, e, b'__init__.py')
             if not os.path.exists(path):
                 continue
         if name in exts or name in _order or name == b'__init__':
             continue
         exts[name] = path
     for name, path in pycompat.iteritems(_disabledextensions):
         # If no path was provided for a disabled extension (e.g. "color=!"),
         # don't replace the path we already found by the scan above.
         if path:
             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] == b'#' or not line.strip():
         line = file.readline()
         if not line:
             break
 
     start = line[:3]
     if start == b'"""' or start == b"'''":
         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 b''.join(result)
 
 
 def _disabledhelp(path):
     '''retrieve help synopsis of a disabled extension (without importing)'''
     try:
         with open(path, b'rb') as src:
             doc = _moduledoc(src)
     except IOError:
         return
 
     if doc:  # extracting localized synopsis
         return gettext(doc)
     else:
         return _(b'(no help text available)')
 
 
 def disabled():
     '''find disabled extensions from hgext. returns a dict of {name: desc}'''
     try:
         from hgext import __index__  # pytype: disable=import-error
 
         return {
             name: gettext(desc)
             for name, desc in pycompat.iteritems(__index__.docs)
             if name not in _order
         }
     except (ImportError, AttributeError):
         pass
 
     paths = _disabledpaths()
     if not paths:
         return {}
 
     exts = {}
     for name, path in pycompat.iteritems(paths):
         doc = _disabledhelp(path)
         if doc:
             exts[name] = doc.splitlines()[0]
 
     return exts
 
 
 def disabled_help(name):
     """Obtain the full help text for a disabled extension, or None."""
     paths = _disabledpaths()
     if name in paths:
         return _disabledhelp(paths[name])
 
 
 def _walkcommand(node):
     """Scan @command() decorators in the tree starting at node"""
     todo = collections.deque([node])
     while todo:
         node = todo.popleft()
         if not isinstance(node, ast.FunctionDef):
             todo.extend(ast.iter_child_nodes(node))
             continue
         for d in node.decorator_list:
             if not isinstance(d, ast.Call):
                 continue
             if not isinstance(d.func, ast.Name):
                 continue
             if d.func.id != 'command':
                 continue
             yield d
 
 
 def _disabledcmdtable(path):
     """Construct a dummy command table without loading the extension module
 
     This may raise IOError or SyntaxError.
     """
     with open(path, b'rb') as src:
         root = ast.parse(src.read(), path)
     cmdtable = {}
     for node in _walkcommand(root):
         if not node.args:
             continue
         a = node.args[0]
         if isinstance(a, ast.Str):
             name = pycompat.sysbytes(a.s)
         elif pycompat.ispy3 and isinstance(a, ast.Bytes):
             name = a.s
         else:
             continue
         cmdtable[name] = (None, [], b'')
     return cmdtable
 
 
 def _finddisabledcmd(ui, cmd, name, path, strict):
     try:
         cmdtable = _disabledcmdtable(path)
     except (IOError, SyntaxError):
         return
     try:
         aliases, entry = cmdutil.findcmd(cmd, cmdtable, strict)
     except (error.AmbiguousCommand, error.UnknownCommand):
         return
     for c in aliases:
         if c.startswith(cmd):
             cmd = c
             break
     else:
         cmd = aliases[0]
     doc = _disabledhelp(path)
     return (cmd, name, doc)
 
 
 def disabledcmd(ui, cmd, strict=False):
     '''find cmd from disabled extensions without importing.
     returns (cmdname, extname, doc)'''
 
     paths = _disabledpaths()
     if not paths:
         raise error.UnknownCommand(cmd)
 
     ext = None
     # first, search for an extension with the same name as the command
     path = paths.pop(cmd, None)
     if path:
         ext = _finddisabledcmd(ui, cmd, cmd, path, strict=strict)
     if not ext:
         # otherwise, interrogate each extension until there's a match
         for name, path in pycompat.iteritems(paths):
             ext = _finddisabledcmd(ui, cmd, name, path, strict=strict)
             if ext:
                 break
     if ext:
         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 _(b'(no help text available)')
         if shortname:
             ename = ename.split(b'.')[-1]
         exts[ename] = doc.splitlines()[0].strip()
 
     return exts
 
 
 def notloaded():
     '''return short names of extensions that failed to load'''
     return [
         name for name, mod in pycompat.iteritems(_extensions) if mod is None
     ]
 
 
 def moduleversion(module):
     '''return version information from given module as a string'''
     if util.safehasattr(module, b'getversion') and callable(module.getversion):
         version = module.getversion()
     elif util.safehasattr(module, b'__version__'):
         version = module.__version__
     else:
         version = b''
     if isinstance(version, (list, tuple)):
         version = b'.'.join(pycompat.bytestr(o) for o in version)
     return version
 
 
 def ismoduleinternal(module):
     exttestedwith = getattr(module, 'testedwith', None)
     return exttestedwith == b"ships-with-hg-core"