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comparison mercurial/demandimport.py @ 3886:abaee83ce0a6

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Replace demandload with new demandimport
author Matt Mackall <mpm@selenic.com>
date Wed, 13 Dec 2006 13:27:09 -0600
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children 3b628b5da9e9 f47afa2401a2
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3885:1e0b94cfba0e 3886:abaee83ce0a6
1 # demandimport.py - global demand-loading of modules for Mercurial
2 #
3 # Copyright 2006 Matt Mackall <mpm@selenic.com>
4 #
5 # This software may be used and distributed according to the terms
6 # of the GNU General Public License, incorporated herein by reference.
7
8 '''
9 demandimport - automatic demandloading of modules
10
11 To enable this module, do:
12
13 import demandimport; demandimport.enable()
14
15 Imports of the following forms will be demand-loaded:
16
17 import a, b.c
18 import a.b as c
19 from a import b,c # a will be loaded immediately
20
21 These imports will not be delayed:
22
23 from a import *
24 b = __import__(a)
25 '''
26
27 _origimport = __import__
28
29 class _demandmod(object):
30 """module demand-loader and proxy"""
31 def __init__(self, name, globals, locals):
32 if '.' in name:
33 head, rest = name.split('.', 1)
34 after = [rest]
35 else:
36 head = name
37 after = []
38 self.__dict__["_data"] = (head, globals, locals, after)
39 self.__dict__["_module"] = None
40 def _extend(self, name):
41 """add to the list of submodules to load"""
42 self._data[3].append(name)
43 def _load(self):
44 if not self._module:
45 head, globals, locals, after = self._data
46 mod = _origimport(head, globals, locals)
47 # load submodules
48 for x in after:
49 hx = x
50 if '.' in x:
51 hx = x.split('.')[0]
52 if not hasattr(mod, hx):
53 setattr(mod, hx, _demandmod(x, mod.__dict__, mod.__dict__))
54 # are we in the locals dictionary still?
55 if locals and locals.get(head) == self:
56 locals[head] = mod
57 self.__dict__["_module"] = mod
58 def __repr__(self):
59 return "<unloaded module '%s'>" % self._data[0]
60 def __call__(self, *args, **kwargs):
61 raise TypeError("'unloaded module' object is not callable")
62 def __getattr__(self, attr):
63 self._load()
64 return getattr(self._module, attr)
65 def __setattr__(self, attr, val):
66 self._load()
67 setattr(self._module, attr, val)
68
69 def _demandimport(name, globals=None, locals=None, fromlist=None):
70 if not locals or name in ignore or fromlist == ('*',):
71 # these cases we can't really delay
72 return _origimport(name, globals, locals, fromlist)
73 elif not fromlist:
74 # import a [as b]
75 if '.' in name: # a.b
76 base, rest = name.split('.', 1)
77 # if a is already demand-loaded, add b to its submodule list
78 if base in locals:
79 if isinstance(locals[base], _demandmod):
80 locals[base]._extend(rest)
81 return locals[base]
82 return _demandmod(name, globals, locals)
83 else:
84 # from a import b,c,d
85 mod = _origimport(name, globals, locals)
86 # recurse down the module chain
87 for comp in name.split('.')[1:]:
88 mod = getattr(mod, comp)
89 for x in fromlist:
90 # set requested submodules for demand load
91 if not(hasattr(mod, x)):
92 setattr(mod, x, _demandmod(x, mod.__dict__, mod.__dict__))
93 return mod
94
95 ignore = []
96
97 def enable():
98 "enable global demand-loading of modules"
99 __builtins__["__import__"] = _demandimport
100
101 def disable():
102 "disable global demand-loading of modules"
103 __builtins__["__import__"] = _origimport
104