wrapfunction: use functools.partial if possible

Every `extensions.bind` call inserts a frame in traceback:

   ... in closure
     return func(*(args + a), **kw)

which makes traceback noisy.

The Python stdlib has a `functools.partial` which is backed by C code and
does not pollute traceback. However it does not support instancemethod and
sets `args` attribute which could be problematic for alias handling.

This patch makes `wrapfunction` use `functools.partial` if we are wrapping a
function directly exported by a module (so it's impossible to be a class or
instance method), and special handles `wrapfunction` results so alias
handling code could handle `args` just fine.

As an example, `hg rebase -s . -d . --traceback` got 6 lines removed in my
setup:

   File "hg/mercurial/dispatch.py", line 898, in _dispatch
     cmdpats, cmdoptions)
  -File "hg/mercurial/extensions.py", line 333, in closure
  -  return func(*(args + a), **kw)
   File "hg/hgext/journal.py", line 84, in runcommand
     return orig(lui, repo, cmd, fullargs, *args)
  -File "hg/mercurial/extensions.py", line 333, in closure
  -  return func(*(args + a), **kw)
   File "fb-hgext/hgext3rd/fbamend/hiddenoverride.py", line 119, in runcommand
     result = orig(lui, repo, cmd, fullargs, *args)
   File "hg/mercurial/dispatch.py", line 660, in runcommand
     ret = _runcommand(ui, options, cmd, d)
  -File "hg/mercurial/extensions.py", line 333, in closure
  -  return func(*(args + a), **kw)
   File "hg/hgext/pager.py", line 69, in pagecmd
     return orig(ui, options, cmd, cmdfunc)
   ....

Differential Revision: https://phab.mercurial-scm.org/D632

mercurial/dispatch.py

@@ -357,7 +357,10 b' def _callcatch(ui, func):'
     return -1
 
 def aliasargs(fn, givenargs):
-    args = getattr(fn, 'args', [])
+    args = []
+    # only care about alias 'args', ignore 'args' set by extensions.wrapfunction
+    if not util.safehasattr(fn, '_origfunc'):
+        args = getattr(fn, 'args', args)
     if args:
         cmd = ' '.join(map(util.shellquote, args))
 

mercurial/extensions.py

@@ -7,6 +7,7 b''
 
 from __future__ import absolute_import
 
+import functools
 import imp
 import inspect
 import os
@@ -332,6 +333,7 b' def bind(func, *args):'
 
 def _updatewrapper(wrap, origfn, unboundwrapper):
     '''Copy and add some useful attributes to wrapper'''
+    wrap.__name__ = origfn.__name__
     wrap.__module__ = getattr(origfn, '__module__')
     wrap.__doc__ = getattr(origfn, '__doc__')
     wrap.__dict__.update(getattr(origfn, '__dict__', {}))
@@ -459,7 +461,14 b' def wrapfunction(container, funcname, wr'
 
     origfn = getattr(container, funcname)
     assert callable(origfn)
-    wrap = bind(wrapper, 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