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1 | # demandimportpy3 - global demand-loading of modules for Mercurial |
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1 | # demandimportpy3 - global demand-loading of modules for Mercurial | |
2 | # |
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2 | # | |
3 | # Copyright 2017 Facebook Inc. |
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3 | # Copyright 2017 Facebook Inc. | |
4 | # |
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4 | # | |
5 | # This software may be used and distributed according to the terms of the |
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5 | # This software may be used and distributed according to the terms of the | |
6 | # GNU General Public License version 2 or any later version. |
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6 | # GNU General Public License version 2 or any later version. | |
7 |
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7 | |||
8 | """Lazy loading for Python 3.6 and above. |
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8 | """Lazy loading for Python 3.6 and above. | |
9 |
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9 | |||
10 | This uses the new importlib finder/loader functionality available in Python 3.5 |
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10 | This uses the new importlib finder/loader functionality available in Python 3.5 | |
11 | and up. The code reuses most of the mechanics implemented inside importlib.util, |
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11 | and up. The code reuses most of the mechanics implemented inside importlib.util, | |
12 | but with a few additions: |
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12 | but with a few additions: | |
13 |
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13 | |||
14 | * Allow excluding certain modules from lazy imports. |
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14 | * Allow excluding certain modules from lazy imports. | |
15 | * Expose an interface that's substantially the same as demandimport for |
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15 | * Expose an interface that's substantially the same as demandimport for | |
16 | Python 2. |
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16 | Python 2. | |
17 |
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17 | |||
18 | This also has some limitations compared to the Python 2 implementation: |
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18 | This also has some limitations compared to the Python 2 implementation: | |
19 |
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19 | |||
20 | * Much of the logic is per-package, not per-module, so any packages loaded |
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20 | * Much of the logic is per-package, not per-module, so any packages loaded | |
21 | before demandimport is enabled will not be lazily imported in the future. In |
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21 | before demandimport is enabled will not be lazily imported in the future. In | |
22 | practice, we only expect builtins to be loaded before demandimport is |
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22 | practice, we only expect builtins to be loaded before demandimport is | |
23 | enabled. |
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23 | enabled. | |
24 | """ |
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24 | """ | |
25 |
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25 | |||
26 | # This line is unnecessary, but it satisfies test-check-py3-compat.t. |
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26 | # This line is unnecessary, but it satisfies test-check-py3-compat.t. | |
27 | from __future__ import absolute_import |
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27 | from __future__ import absolute_import | |
28 |
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28 | |||
29 | import contextlib |
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29 | import contextlib | |
30 | import importlib.abc |
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30 | import importlib.abc | |
31 | import importlib.machinery |
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31 | import importlib.machinery | |
32 | import importlib.util |
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32 | import importlib.util | |
33 | import sys |
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33 | import sys | |
34 |
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34 | |||
35 | from . import tracing |
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35 | from . import tracing | |
36 |
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36 | |||
37 | _deactivated = False |
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37 | _deactivated = False | |
38 |
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38 | |||
39 |
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39 | |||
40 | class _lazyloaderex(importlib.util.LazyLoader): |
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40 | class _lazyloaderex(importlib.util.LazyLoader): | |
41 | """This is a LazyLoader except it also follows the _deactivated global and |
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41 | """This is a LazyLoader except it also follows the _deactivated global and | |
42 | the ignore list. |
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42 | the ignore list. | |
43 | """ |
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43 | """ | |
44 |
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44 | |||
45 | def exec_module(self, module): |
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45 | def exec_module(self, module): | |
46 | """Make the module load lazily.""" |
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46 | """Make the module load lazily.""" | |
47 | with tracing.log('demandimport %s', module): |
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47 | with tracing.log('demandimport %s', module): | |
48 | if _deactivated or module.__name__ in ignores: |
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48 | if _deactivated or module.__name__ in ignores: | |
49 | self.loader.exec_module(module) |
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49 | self.loader.exec_module(module) | |
50 | else: |
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50 | else: | |
51 | super().exec_module(module) |
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51 | super().exec_module(module) | |
52 |
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52 | |||
53 |
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53 | |||
54 | # This is 3.6+ because with Python 3.5 it isn't possible to lazily load |
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54 | # This is 3.6+ because with Python 3.5 it isn't possible to lazily load | |
55 | # extensions. See the discussion in https://bugs.python.org/issue26186 for more. |
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55 | # extensions. See the discussion in https://bugs.python.org/issue26186 for more. | |
56 | _extensions_loader = _lazyloaderex.factory( |
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56 | if sys.version_info[0:2] >= (3, 6): | |
57 | importlib.machinery.ExtensionFileLoader |
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57 | _extensions_loader = _lazyloaderex.factory( | |
58 | ) |
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58 | importlib.machinery.ExtensionFileLoader | |
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59 | ) | |||
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60 | else: | |||
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61 | _extensions_loader = importlib.machinery.ExtensionFileLoader | |||
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62 | ||||
59 | _bytecode_loader = _lazyloaderex.factory( |
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63 | _bytecode_loader = _lazyloaderex.factory( | |
60 | importlib.machinery.SourcelessFileLoader |
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64 | importlib.machinery.SourcelessFileLoader | |
61 | ) |
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65 | ) | |
62 | _source_loader = _lazyloaderex.factory(importlib.machinery.SourceFileLoader) |
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66 | _source_loader = _lazyloaderex.factory(importlib.machinery.SourceFileLoader) | |
63 |
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67 | |||
64 |
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68 | |||
65 | def _makefinder(path): |
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69 | def _makefinder(path): | |
66 | return importlib.machinery.FileFinder( |
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70 | return importlib.machinery.FileFinder( | |
67 | path, |
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71 | path, | |
68 | # This is the order in which loaders are passed in in core Python. |
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72 | # This is the order in which loaders are passed in in core Python. | |
69 | (_extensions_loader, importlib.machinery.EXTENSION_SUFFIXES), |
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73 | (_extensions_loader, importlib.machinery.EXTENSION_SUFFIXES), | |
70 | (_source_loader, importlib.machinery.SOURCE_SUFFIXES), |
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74 | (_source_loader, importlib.machinery.SOURCE_SUFFIXES), | |
71 | (_bytecode_loader, importlib.machinery.BYTECODE_SUFFIXES), |
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75 | (_bytecode_loader, importlib.machinery.BYTECODE_SUFFIXES), | |
72 | ) |
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76 | ) | |
73 |
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77 | |||
74 |
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78 | |||
75 | ignores = set() |
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79 | ignores = set() | |
76 |
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80 | |||
77 |
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81 | |||
78 | def init(ignoreset): |
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82 | def init(ignoreset): | |
79 | global ignores |
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83 | global ignores | |
80 | ignores = ignoreset |
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84 | ignores = ignoreset | |
81 |
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85 | |||
82 |
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86 | |||
83 | def isenabled(): |
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87 | def isenabled(): | |
84 | return _makefinder in sys.path_hooks and not _deactivated |
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88 | return _makefinder in sys.path_hooks and not _deactivated | |
85 |
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89 | |||
86 |
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90 | |||
87 | def disable(): |
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91 | def disable(): | |
88 | try: |
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92 | try: | |
89 | while True: |
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93 | while True: | |
90 | sys.path_hooks.remove(_makefinder) |
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94 | sys.path_hooks.remove(_makefinder) | |
91 | except ValueError: |
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95 | except ValueError: | |
92 | pass |
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96 | pass | |
93 |
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97 | |||
94 |
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98 | |||
95 | def enable(): |
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99 | def enable(): | |
96 | sys.path_hooks.insert(0, _makefinder) |
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100 | sys.path_hooks.insert(0, _makefinder) | |
97 |
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101 | |||
98 |
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102 | |||
99 | @contextlib.contextmanager |
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103 | @contextlib.contextmanager | |
100 | def deactivated(): |
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104 | def deactivated(): | |
101 | # This implementation is a bit different from Python 2's. Python 3 |
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105 | # This implementation is a bit different from Python 2's. Python 3 | |
102 | # maintains a per-package finder cache in sys.path_importer_cache (see |
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106 | # maintains a per-package finder cache in sys.path_importer_cache (see | |
103 | # PEP 302). This means that we can't just call disable + enable. |
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107 | # PEP 302). This means that we can't just call disable + enable. | |
104 | # If we do that, in situations like: |
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108 | # If we do that, in situations like: | |
105 | # |
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109 | # | |
106 | # demandimport.enable() |
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110 | # demandimport.enable() | |
107 | # ... |
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111 | # ... | |
108 | # from foo.bar import mod1 |
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112 | # from foo.bar import mod1 | |
109 | # with demandimport.deactivated(): |
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113 | # with demandimport.deactivated(): | |
110 | # from foo.bar import mod2 |
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114 | # from foo.bar import mod2 | |
111 | # |
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115 | # | |
112 | # mod2 will be imported lazily. (The converse also holds -- whatever finder |
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116 | # mod2 will be imported lazily. (The converse also holds -- whatever finder | |
113 | # first gets cached will be used.) |
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117 | # first gets cached will be used.) | |
114 | # |
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118 | # | |
115 | # Instead, have a global flag the LazyLoader can use. |
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119 | # Instead, have a global flag the LazyLoader can use. | |
116 | global _deactivated |
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120 | global _deactivated | |
117 | demandenabled = isenabled() |
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121 | demandenabled = isenabled() | |
118 | if demandenabled: |
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122 | if demandenabled: | |
119 | _deactivated = True |
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123 | _deactivated = True | |
120 | try: |
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124 | try: | |
121 | yield |
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125 | yield | |
122 | finally: |
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126 | finally: | |
123 | if demandenabled: |
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127 | if demandenabled: | |
124 | _deactivated = False |
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128 | _deactivated = False |
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