hook: disable demandimport before importing hooks

This solved an obscure bug for me. In upgrading Distribute on the server, a
patch was added to has a try: import a except ImportError thing that's only
supposed to work with Python 3.3. I'm using 2.7. My hook failed with an
ImportError because of this. It seems kind of sensible to turn off
demandimport before importing the hook, since the except ImportError pattern
is used quite a bit in Python code (including in other Distribute code).

mercurial/hook.py

@@ -1,189 +1,193
 # hook.py - hook support for mercurial
 #
 # Copyright 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 i18n import _
 import os, sys
-import extensions, util
+import extensions, util, demandimport
 
 def _pythonhook(ui, repo, name, hname, funcname, args, throw):
     '''call python hook. hook is callable object, looked up as
     name in python module. if callable returns "true", hook
     fails, else passes. if hook raises exception, treated as
     hook failure. exception propagates if throw is "true".
 
     reason for "true" meaning "hook failed" is so that
     unmodified commands (e.g. mercurial.commands.update) can
     be run as hooks without wrappers to convert return values.'''
 
     ui.note(_("calling hook %s: %s\n") % (hname, funcname))
     obj = funcname
     if not util.safehasattr(obj, '__call__'):
         d = funcname.rfind('.')
         if d == -1:
             raise util.Abort(_('%s hook is invalid ("%s" not in '
                                'a module)') % (hname, funcname))
         modname = funcname[:d]
         oldpaths = sys.path
         if util.mainfrozen():
             # binary installs require sys.path manipulation
             modpath, modfile = os.path.split(modname)
             if modpath and modfile:
                 sys.path = sys.path[:] + [modpath]
                 modname = modfile
         try:
+            demandimport.disable()
             obj = __import__(modname)
+            demandimport.enable()
         except ImportError:
             e1 = sys.exc_type, sys.exc_value, sys.exc_traceback
             try:
                 # extensions are loaded with hgext_ prefix
                 obj = __import__("hgext_%s" % modname)
+                demandimport.enable()
             except ImportError:
+                demandimport.enable()
                 e2 = sys.exc_type, sys.exc_value, sys.exc_traceback
                 if ui.tracebackflag:
                     ui.warn(_('exception from first failed import attempt:\n'))
                 ui.traceback(e1)
                 if ui.tracebackflag:
                     ui.warn(_('exception from second failed import attempt:\n'))
                 ui.traceback(e2)
                 raise util.Abort(_('%s hook is invalid '
                                    '(import of "%s" failed)') %
                                  (hname, modname))
         sys.path = oldpaths
         try:
             for p in funcname.split('.')[1:]:
                 obj = getattr(obj, p)
         except AttributeError:
             raise util.Abort(_('%s hook is invalid '
                                '("%s" is not defined)') %
                              (hname, funcname))
         if not util.safehasattr(obj, '__call__'):
             raise util.Abort(_('%s hook is invalid '
                                '("%s" is not callable)') %
                              (hname, funcname))
     try:
         try:
             # redirect IO descriptors to the ui descriptors so hooks
             # that write directly to these don't mess up the command
             # protocol when running through the command server
             old = sys.stdout, sys.stderr, sys.stdin
             sys.stdout, sys.stderr, sys.stdin = ui.fout, ui.ferr, ui.fin
 
             r = obj(ui=ui, repo=repo, hooktype=name, **args)
         except KeyboardInterrupt:
             raise
         except Exception, exc:
             if isinstance(exc, util.Abort):
                 ui.warn(_('error: %s hook failed: %s\n') %
                              (hname, exc.args[0]))
             else:
                 ui.warn(_('error: %s hook raised an exception: '
                                '%s\n') % (hname, exc))
             if throw:
                 raise
             ui.traceback()
             return True
     finally:
         sys.stdout, sys.stderr, sys.stdin = old
     if r:
         if throw:
             raise util.Abort(_('%s hook failed') % hname)
         ui.warn(_('warning: %s hook failed\n') % hname)
     return r
 
 def _exthook(ui, repo, name, cmd, args, throw):
     ui.note(_("running hook %s: %s\n") % (name, cmd))
 
     env = {}
     for k, v in args.iteritems():
         if util.safehasattr(v, '__call__'):
             v = v()
         if isinstance(v, dict):
             # make the dictionary element order stable across Python
             # implementations
             v = ('{' +
                  ', '.join('%r: %r' % i for i in sorted(v.iteritems())) +
                  '}')
         env['HG_' + k.upper()] = v
 
     if repo:
         cwd = repo.root
     else:
         cwd = os.getcwd()
     if 'HG_URL' in env and env['HG_URL'].startswith('remote:http'):
         r = util.system(cmd, environ=env, cwd=cwd, out=ui)
     else:
         r = util.system(cmd, environ=env, cwd=cwd, out=ui.fout)
     if r:
         desc, r = util.explainexit(r)
         if throw:
             raise util.Abort(_('%s hook %s') % (name, desc))
         ui.warn(_('warning: %s hook %s\n') % (name, desc))
     return r
 
 def _allhooks(ui):
     hooks = []
     for name, cmd in ui.configitems('hooks'):
         if not name.startswith('priority'):
             priority = ui.configint('hooks', 'priority.%s' % name, 0)
             hooks.append((-priority, len(hooks), name, cmd))
     return [(k, v) for p, o, k, v in sorted(hooks)]
 
 _redirect = False
 def redirect(state):
     global _redirect
     _redirect = state
 
 def hook(ui, repo, name, throw=False, **args):
     if not ui.callhooks:
         return False
 
     r = False
     oldstdout = -1
 
     try:
         for hname, cmd in _allhooks(ui):
             if hname.split('.')[0] != name or not cmd:
                 continue
 
             if oldstdout == -1 and _redirect:
                 try:
                     stdoutno = sys.__stdout__.fileno()
                     stderrno = sys.__stderr__.fileno()
                     # temporarily redirect stdout to stderr, if possible
                     if stdoutno >= 0 and stderrno >= 0:
                         sys.__stdout__.flush()
                         oldstdout = os.dup(stdoutno)
                         os.dup2(stderrno, stdoutno)
                 except (OSError, AttributeError):
                     # files seem to be bogus, give up on redirecting (WSGI, etc)
                     pass
 
             if util.safehasattr(cmd, '__call__'):
                 r = _pythonhook(ui, repo, name, hname, cmd, args, throw) or r
             elif cmd.startswith('python:'):
                 if cmd.count(':') >= 2:
                     path, cmd = cmd[7:].rsplit(':', 1)
                     path = util.expandpath(path)
                     if repo:
                         path = os.path.join(repo.root, path)
                     try:
                         mod = extensions.loadpath(path, 'hghook.%s' % hname)
                     except Exception:
                         ui.write(_("loading %s hook failed:\n") % hname)
                         raise
                     hookfn = getattr(mod, cmd)
                 else:
                     hookfn = cmd[7:].strip()
                 r = _pythonhook(ui, repo, name, hname, hookfn, args, throw) or r
             else:
                 r = _exthook(ui, repo, hname, cmd, args, throw) or r
     finally:
         if _redirect and oldstdout >= 0:
             os.dup2(oldstdout, stdoutno)
             os.close(oldstdout)
 
     return r