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1 # demandimport.py - global demand-loading of modules for Mercurial
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2 #
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3 # Copyright 2006, 2007 Matt Mackall <mpm@selenic.com>
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4 #
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5 # This software may be used and distributed according to the terms of the
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6 # GNU General Public License version 2, incorporated herein by reference.
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7
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8 '''
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9 demandimport - automatic demandloading of modules
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10
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11 To enable this module, do:
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12
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13 import demandimport; demandimport.enable()
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14
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15 Imports of the following forms will be demand-loaded:
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16
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17 import a, b.c
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18 import a.b as c
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19 from a import b,c # a will be loaded immediately
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20
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21 These imports will not be delayed:
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22
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23 from a import *
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24 b = __import__(a)
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25 '''
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26
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27 import __builtin__
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28 _origimport = __import__
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29
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30 class _demandmod(object):
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31 """module demand-loader and proxy"""
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32 def __init__(self, name, globals, locals):
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33 if '.' in name:
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34 head, rest = name.split('.', 1)
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35 after = [rest]
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36 else:
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37 head = name
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38 after = []
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39 object.__setattr__(self, "_data", (head, globals, locals, after))
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40 object.__setattr__(self, "_module", None)
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41 def _extend(self, name):
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42 """add to the list of submodules to load"""
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43 self._data[3].append(name)
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44 def _load(self):
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45 if not self._module:
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46 head, globals, locals, after = self._data
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47 mod = _origimport(head, globals, locals)
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48 # load submodules
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49 def subload(mod, p):
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50 h, t = p, None
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51 if '.' in p:
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52 h, t = p.split('.', 1)
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53 if not hasattr(mod, h):
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54 setattr(mod, h, _demandmod(p, mod.__dict__, mod.__dict__))
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55 elif t:
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56 subload(getattr(mod, h), t)
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57
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58 for x in after:
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59 subload(mod, x)
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60
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61 # are we in the locals dictionary still?
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62 if locals and locals.get(head) == self:
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63 locals[head] = mod
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64 object.__setattr__(self, "_module", mod)
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65
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66 def __repr__(self):
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67 if self._module:
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68 return "<proxied module '%s'>" % self._data[0]
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69 return "<unloaded module '%s'>" % self._data[0]
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70 def __call__(self, *args, **kwargs):
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71 raise TypeError("%s object is not callable" % repr(self))
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72 def __getattribute__(self, attr):
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73 if attr in ('_data', '_extend', '_load', '_module'):
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74 return object.__getattribute__(self, attr)
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75 self._load()
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76 return getattr(self._module, attr)
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77 def __setattr__(self, attr, val):
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78 self._load()
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79 setattr(self._module, attr, val)
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80
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81 def _demandimport(name, globals=None, locals=None, fromlist=None, level=None):
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82 if not locals or name in ignore or fromlist == ('*',):
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83 # these cases we can't really delay
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84 return _origimport(name, globals, locals, fromlist)
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85 elif not fromlist:
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86 # import a [as b]
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87 if '.' in name: # a.b
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88 base, rest = name.split('.', 1)
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89 # email.__init__ loading email.mime
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90 if globals and globals.get('__name__', None) == base:
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91 return _origimport(name, globals, locals, fromlist)
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92 # if a is already demand-loaded, add b to its submodule list
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93 if base in locals:
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94 if isinstance(locals[base], _demandmod):
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95 locals[base]._extend(rest)
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96 return locals[base]
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97 return _demandmod(name, globals, locals)
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98 else:
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99 if level is not None:
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100 # from . import b,c,d or from .a import b,c,d
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101 return _origimport(name, globals, locals, fromlist, level)
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102 # from a import b,c,d
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103 mod = _origimport(name, globals, locals)
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104 # recurse down the module chain
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105 for comp in name.split('.')[1:]:
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106 if not hasattr(mod, comp):
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107 setattr(mod, comp, _demandmod(comp, mod.__dict__, mod.__dict__))
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108 mod = getattr(mod, comp)
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109 for x in fromlist:
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110 # set requested submodules for demand load
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111 if not(hasattr(mod, x)):
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112 setattr(mod, x, _demandmod(x, mod.__dict__, locals))
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113 return mod
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114
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115 ignore = [
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116 '_hashlib',
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117 '_xmlplus',
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118 'fcntl',
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119 'win32com.gen_py',
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120 'pythoncom',
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121 # imported by tarfile, not available under Windows
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122 'pwd',
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123 'grp',
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124 # imported by profile, itself imported by hotshot.stats,
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125 # not available under Windows
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126 'resource',
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127 ]
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128
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129 def enable():
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130 "enable global demand-loading of modules"
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131 __builtin__.__import__ = _demandimport
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132
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133 def disable():
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134 "disable global demand-loading of modules"
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135 __builtin__.__import__ = _origimport
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136
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