From patchwork Sat May 10 23:39:55 2014
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Subject: [1,of,3] demandimport: pass proper level to __import__ in Python 3
From: Gregory Szorc <gregory.szorc@gmail.com>
X-Patchwork-Id: 4726
Message-Id: <c59dd2bd4a28c4ce6438.1399765195@vm-ubuntu-main.gateway.sonic.net>
To: mercurial-devel@selenic.com
Date: Sat, 10 May 2014 16:39:55 -0700

# HG changeset patch
# User Gregory Szorc <gregory.szorc@gmail.com>
# Date 1399759045 25200
#      Sat May 10 14:57:25 2014 -0700
# Node ID c59dd2bd4a28c4ce6438f15c9cfa612bb1e74162
# Parent  bcddddcf0b540b1d98f0dc1f1a1bef9337e2e567
demandimport: pass proper level to __import__ in Python 3

demandimport was failing in Python 3 with a ValueError because
__import__'s level=-1 has gone away (-1 means to try both relative
and absolute imports and relative imports don't exist in Python 3).

With this patch, demandimport still doesn't work in Python 3 (it
fails when importing a non-package module).

diff --git a/mercurial/demandimport.py b/mercurial/demandimport.py
--- a/mercurial/demandimport.py
+++ b/mercurial/demandimport.py
@@ -23,15 +23,19 @@ These imports will not be delayed:
   from a import *
   b = __import__(a)
 '''
 
-import __builtin__, os
+import __builtin__, os, sys
 _origimport = __import__
 
 nothing = object()
 
 try:
-    _origimport(__builtin__.__name__, {}, {}, None, -1)
+    # Python 3 doesn't have relative imports nor level -1.
+    level = -1
+    if sys.version_info[0] >= 3:
+        level = 0
+    _origimport(__builtin__.__name__, {}, {}, None, level)
 except TypeError: # no level argument
     def _import(name, globals, locals, fromlist, level):
         "call _origimport with no level argument"
         return _origimport(name, globals, locals, fromlist)
@@ -54,9 +58,9 @@ def _hgextimport(importfunc, name, globa
         return importfunc(hgextname, globals, *args)
 
 class _demandmod(object):
     """module demand-loader and proxy"""
-    def __init__(self, name, globals, locals, level=-1):
+    def __init__(self, name, globals, locals, level=level):
         if '.' in name:
             head, rest = name.split('.', 1)
             after = [rest]
         else:
@@ -104,9 +108,9 @@ class _demandmod(object):
     def __setattr__(self, attr, val):
         self._load()
         setattr(self._module, attr, val)
 
-def _demandimport(name, globals=None, locals=None, fromlist=None, level=-1):
+def _demandimport(name, globals=None, locals=None, fromlist=None, level=level):
     if not locals or name in ignore or fromlist == ('*',):
         # these cases we can't really delay
         return _hgextimport(_import, name, globals, locals, fromlist, level)
     elif not fromlist: