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 or any later version. |
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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 from __future__ import absolute_import |
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28 |
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29 import contextlib |
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30 import os |
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31 import sys |
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32 |
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33 # __builtin__ in Python 2, builtins in Python 3. |
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34 try: |
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35 import __builtin__ as builtins |
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36 except ImportError: |
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37 import builtins |
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38 |
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39 contextmanager = contextlib.contextmanager |
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40 |
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41 _origimport = __import__ |
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42 |
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43 nothing = object() |
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44 |
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45 # Python 3 doesn't have relative imports nor level -1. |
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46 level = -1 |
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47 if sys.version_info[0] >= 3: |
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48 level = 0 |
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49 _import = _origimport |
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50 |
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51 def _hgextimport(importfunc, name, globals, *args, **kwargs): |
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52 try: |
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53 return importfunc(name, globals, *args, **kwargs) |
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54 except ImportError: |
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55 if not globals: |
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56 raise |
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57 # extensions are loaded with "hgext_" prefix |
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58 hgextname = 'hgext_%s' % name |
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59 nameroot = hgextname.split('.', 1)[0] |
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60 contextroot = globals.get('__name__', '').split('.', 1)[0] |
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61 if nameroot != contextroot: |
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62 raise |
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63 # retry to import with "hgext_" prefix |
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64 return importfunc(hgextname, globals, *args, **kwargs) |
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65 |
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66 class _demandmod(object): |
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67 """module demand-loader and proxy |
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68 |
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69 Specify 1 as 'level' argument at construction, to import module |
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70 relatively. |
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71 """ |
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72 def __init__(self, name, globals, locals, level): |
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73 if '.' in name: |
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74 head, rest = name.split('.', 1) |
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75 after = [rest] |
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76 else: |
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77 head = name |
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78 after = [] |
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79 object.__setattr__(self, r"_data", |
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80 (head, globals, locals, after, level, set())) |
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81 object.__setattr__(self, r"_module", None) |
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82 def _extend(self, name): |
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83 """add to the list of submodules to load""" |
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84 self._data[3].append(name) |
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85 |
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86 def _addref(self, name): |
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87 """Record that the named module ``name`` imports this module. |
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88 |
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89 References to this proxy class having the name of this module will be |
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90 replaced at module load time. We assume the symbol inside the importing |
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91 module is identical to the "head" name of this module. We don't |
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92 actually know if "as X" syntax is being used to change the symbol name |
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93 because this information isn't exposed to __import__. |
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94 """ |
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95 self._data[5].add(name) |
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96 |
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97 def _load(self): |
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98 if not self._module: |
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99 head, globals, locals, after, level, modrefs = self._data |
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100 mod = _hgextimport(_import, head, globals, locals, None, level) |
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101 if mod is self: |
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102 # In this case, _hgextimport() above should imply |
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103 # _demandimport(). Otherwise, _hgextimport() never |
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104 # returns _demandmod. This isn't intentional behavior, |
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105 # in fact. (see also issue5304 for detail) |
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106 # |
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107 # If self._module is already bound at this point, self |
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108 # should be already _load()-ed while _hgextimport(). |
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109 # Otherwise, there is no way to import actual module |
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110 # as expected, because (re-)invoking _hgextimport() |
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111 # should cause same result. |
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112 # This is reason why _load() returns without any more |
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113 # setup but assumes self to be already bound. |
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114 mod = self._module |
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115 assert mod and mod is not self, "%s, %s" % (self, mod) |
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116 return |
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117 |
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118 # load submodules |
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119 def subload(mod, p): |
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120 h, t = p, None |
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121 if '.' in p: |
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122 h, t = p.split('.', 1) |
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123 if getattr(mod, h, nothing) is nothing: |
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124 setattr(mod, h, _demandmod(p, mod.__dict__, mod.__dict__, |
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125 level=1)) |
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126 elif t: |
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127 subload(getattr(mod, h), t) |
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128 |
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129 for x in after: |
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130 subload(mod, x) |
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131 |
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132 # Replace references to this proxy instance with the actual module. |
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133 if locals and locals.get(head) == self: |
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134 locals[head] = mod |
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135 |
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136 for modname in modrefs: |
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137 modref = sys.modules.get(modname, None) |
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138 if modref and getattr(modref, head, None) == self: |
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139 setattr(modref, head, mod) |
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140 |
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141 object.__setattr__(self, r"_module", mod) |
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142 |
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143 def __repr__(self): |
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144 if self._module: |
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145 return "<proxied module '%s'>" % self._data[0] |
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146 return "<unloaded module '%s'>" % self._data[0] |
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147 def __call__(self, *args, **kwargs): |
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148 raise TypeError("%s object is not callable" % repr(self)) |
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149 def __getattribute__(self, attr): |
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150 if attr in ('_data', '_extend', '_load', '_module', '_addref'): |
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151 return object.__getattribute__(self, attr) |
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152 self._load() |
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153 return getattr(self._module, attr) |
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154 def __setattr__(self, attr, val): |
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155 self._load() |
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156 setattr(self._module, attr, val) |
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157 |
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158 _pypy = '__pypy__' in sys.builtin_module_names |
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159 |
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160 def _demandimport(name, globals=None, locals=None, fromlist=None, level=level): |
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161 if not locals or name in ignore or fromlist == ('*',): |
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162 # these cases we can't really delay |
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163 return _hgextimport(_import, name, globals, locals, fromlist, level) |
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164 elif not fromlist: |
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165 # import a [as b] |
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166 if '.' in name: # a.b |
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167 base, rest = name.split('.', 1) |
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168 # email.__init__ loading email.mime |
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169 if globals and globals.get('__name__', None) == base: |
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170 return _import(name, globals, locals, fromlist, level) |
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171 # if a is already demand-loaded, add b to its submodule list |
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172 if base in locals: |
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173 if isinstance(locals[base], _demandmod): |
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174 locals[base]._extend(rest) |
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175 return locals[base] |
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176 return _demandmod(name, globals, locals, level) |
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177 else: |
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178 # There is a fromlist. |
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179 # from a import b,c,d |
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180 # from . import b,c,d |
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181 # from .a import b,c,d |
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182 |
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183 # level == -1: relative and absolute attempted (Python 2 only). |
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184 # level >= 0: absolute only (Python 2 w/ absolute_import and Python 3). |
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185 # The modern Mercurial convention is to use absolute_import everywhere, |
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186 # so modern Mercurial code will have level >= 0. |
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187 |
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188 # The name of the module the import statement is located in. |
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189 globalname = globals.get('__name__') |
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190 |
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191 def processfromitem(mod, attr): |
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192 """Process an imported symbol in the import statement. |
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193 |
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194 If the symbol doesn't exist in the parent module, and if the |
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195 parent module is a package, it must be a module. We set missing |
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196 modules up as _demandmod instances. |
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197 """ |
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198 symbol = getattr(mod, attr, nothing) |
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199 nonpkg = getattr(mod, '__path__', nothing) is nothing |
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200 if symbol is nothing: |
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201 if nonpkg: |
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202 # do not try relative import, which would raise ValueError, |
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203 # and leave unknown attribute as the default __import__() |
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204 # would do. the missing attribute will be detected later |
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205 # while processing the import statement. |
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206 return |
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207 mn = '%s.%s' % (mod.__name__, attr) |
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208 if mn in ignore: |
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209 importfunc = _origimport |
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210 else: |
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211 importfunc = _demandmod |
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212 symbol = importfunc(attr, mod.__dict__, locals, level=1) |
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213 setattr(mod, attr, symbol) |
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214 |
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215 # Record the importing module references this symbol so we can |
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216 # replace the symbol with the actual module instance at load |
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217 # time. |
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218 if globalname and isinstance(symbol, _demandmod): |
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219 symbol._addref(globalname) |
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220 |
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221 def chainmodules(rootmod, modname): |
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222 # recurse down the module chain, and return the leaf module |
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223 mod = rootmod |
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224 for comp in modname.split('.')[1:]: |
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225 if getattr(mod, comp, nothing) is nothing: |
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226 setattr(mod, comp, _demandmod(comp, mod.__dict__, |
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227 mod.__dict__, level=1)) |
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228 mod = getattr(mod, comp) |
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229 return mod |
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230 |
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231 if level >= 0: |
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232 if name: |
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233 # "from a import b" or "from .a import b" style |
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234 rootmod = _hgextimport(_origimport, name, globals, locals, |
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235 level=level) |
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236 mod = chainmodules(rootmod, name) |
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237 elif _pypy: |
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238 # PyPy's __import__ throws an exception if invoked |
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239 # with an empty name and no fromlist. Recreate the |
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240 # desired behaviour by hand. |
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241 mn = globalname |
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242 mod = sys.modules[mn] |
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243 if getattr(mod, '__path__', nothing) is nothing: |
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244 mn = mn.rsplit('.', 1)[0] |
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245 mod = sys.modules[mn] |
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246 if level > 1: |
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247 mn = mn.rsplit('.', level - 1)[0] |
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248 mod = sys.modules[mn] |
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249 else: |
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250 mod = _hgextimport(_origimport, name, globals, locals, |
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251 level=level) |
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252 |
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253 for x in fromlist: |
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254 processfromitem(mod, x) |
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255 |
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256 return mod |
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257 |
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258 # But, we still need to support lazy loading of standard library and 3rd |
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259 # party modules. So handle level == -1. |
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260 mod = _hgextimport(_origimport, name, globals, locals) |
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261 mod = chainmodules(mod, name) |
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262 |
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263 for x in fromlist: |
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264 processfromitem(mod, x) |
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265 |
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266 return mod |
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267 |
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268 ignore = [ |
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269 '__future__', |
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270 '_hashlib', |
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271 # ImportError during pkg_resources/__init__.py:fixup_namespace_package |
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272 '_imp', |
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273 '_xmlplus', |
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274 'fcntl', |
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275 'nt', # pathlib2 tests the existence of built-in 'nt' module |
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276 'win32com.gen_py', |
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277 'win32com.shell', # 'appdirs' tries to import win32com.shell |
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278 '_winreg', # 2.7 mimetypes needs immediate ImportError |
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279 'pythoncom', |
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280 # imported by tarfile, not available under Windows |
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281 'pwd', |
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282 'grp', |
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283 # imported by profile, itself imported by hotshot.stats, |
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284 # not available under Windows |
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285 'resource', |
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286 # this trips up many extension authors |
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287 'gtk', |
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288 # setuptools' pkg_resources.py expects "from __main__ import x" to |
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289 # raise ImportError if x not defined |
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290 '__main__', |
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291 '_ssl', # conditional imports in the stdlib, issue1964 |
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292 '_sre', # issue4920 |
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293 'rfc822', |
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294 'mimetools', |
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295 'sqlalchemy.events', # has import-time side effects (issue5085) |
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296 # setuptools 8 expects this module to explode early when not on windows |
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297 'distutils.msvc9compiler', |
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298 '__builtin__', |
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299 'builtins', |
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300 ] |
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301 |
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302 if _pypy: |
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303 ignore.extend([ |
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304 # _ctypes.pointer is shadowed by "from ... import pointer" (PyPy 5) |
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305 '_ctypes.pointer', |
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306 ]) |
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307 |
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308 def isenabled(): |
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309 return builtins.__import__ == _demandimport |
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310 |
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311 def enable(): |
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312 "enable global demand-loading of modules" |
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313 if os.environ.get('HGDEMANDIMPORT') != 'disable': |
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314 builtins.__import__ = _demandimport |
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315 |
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316 def disable(): |
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317 "disable global demand-loading of modules" |
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318 builtins.__import__ = _origimport |
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319 |
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320 @contextmanager |
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321 def deactivated(): |
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322 "context manager for disabling demandimport in 'with' blocks" |
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323 demandenabled = isenabled() |
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324 if demandenabled: |
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325 disable() |
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326 |
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327 try: |
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328 yield |
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329 finally: |
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330 if demandenabled: |
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331 enable() |
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