cpython-withatomic / Lib / importlib / _bootstrap.py

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
"""Core implementation of import.

This module is NOT meant to be directly imported! It has been designed such
that it can be bootstrapped into Python as the implementation of import. As
such it requires the injection of specific modules and attributes in order to
work. One should use importlib as the public-facing version of this module.

"""

# Injected modules are '_warnings', 'imp', 'sys', 'marshal', '_io',
# and '_os' (a.k.a. 'posix', 'nt' or 'os2').
# Injected attribute is path_sep.
#
# When editing this code be aware that code executed at import time CANNOT
# reference any injected objects! This includes not only global code but also
# anything specified at the class level.


# Bootstrap-related code ######################################################

# TODO: Expose from marshal
def _w_long(x):
    """Convert a 32-bit integer to little-endian.

    XXX Temporary until marshal's long functions are exposed.

    """
    x = int(x)
    int_bytes = []
    int_bytes.append(x & 0xFF)
    int_bytes.append((x >> 8) & 0xFF)
    int_bytes.append((x >> 16) & 0xFF)
    int_bytes.append((x >> 24) & 0xFF)
    return bytearray(int_bytes)


# TODO: Expose from marshal
def _r_long(int_bytes):
    """Convert 4 bytes in little-endian to an integer.

    XXX Temporary until marshal's long function are exposed.

    """
    x = int_bytes[0]
    x |= int_bytes[1] << 8
    x |= int_bytes[2] << 16
    x |= int_bytes[3] << 24
    return x



# XXX Could also expose Modules/getpath.c:joinpath()
def _path_join(*args):
    """Replacement for os.path.join."""
    return path_sep.join(x[:-len(path_sep)] if x.endswith(path_sep) else x
                            for x in args if x)


def _path_exists(path):
    """Replacement for os.path.exists."""
    try:
        _os.stat(path)
    except OSError:
        return False
    else:
        return True


def _path_is_mode_type(path, mode):
    """Test whether the path is the specified mode type."""
    try:
        stat_info = _os.stat(path)
    except OSError:
        return False
    return (stat_info.st_mode & 0o170000) == mode


# XXX Could also expose Modules/getpath.c:isfile()
def _path_isfile(path):
    """Replacement for os.path.isfile."""
    return _path_is_mode_type(path, 0o100000)


# XXX Could also expose Modules/getpath.c:isdir()
def _path_isdir(path):
    """Replacement for os.path.isdir."""
    if not path:
        path = _os.getcwd()
    return _path_is_mode_type(path, 0o040000)


def _path_without_ext(path, ext_type):
    """Replacement for os.path.splitext()[0]."""
    for suffix in _suffix_list(ext_type):
        if path.endswith(suffix):
            return path[:-len(suffix)]
    else:
        raise ValueError("path is not of the specified type")


def _path_absolute(path):
    """Replacement for os.path.abspath."""
    if not path:
        path = _os.getcwd()
    try:
        return _os._getfullpathname(path)
    except AttributeError:
        if path.startswith('/'):
            return path
        else:
            return _path_join(_os.getcwd(), path)


def _write_atomic(path, data):
    """Best-effort function to write data to a path atomically.
    Be prepared to handle a FileExistsError if concurrent writing of the
    temporary file is attempted."""
    # Renaming should be atomic on most platforms (including Windows).
    # Under Windows, the limitation is that we can't rename() to an existing
    # path, while POSIX will overwrite it. But here we don't really care
    # if there is a glimpse of time during which the final pyc file doesn't
    # exist.
    # id() is used to generate a pseudo-random filename.
    path_tmp = '{}.{}'.format(path, id(path))
    fd = _os.open(path_tmp, _os.O_EXCL | _os.O_CREAT | _os.O_WRONLY, 0o666)
    try:
        with _io.FileIO(fd, 'wb') as file:
            file.write(data)
        try:
            _os.rename(path_tmp, path)
        except FileExistsError:
            # Windows (if we had access to MoveFileEx, we could overwrite)
            _os.unlink(path)
            _os.rename(path_tmp, path)
    except OSError:
        try:
            _os.unlink(path_tmp)
        except OSError:
            pass
        raise


def _wrap(new, old):
    """Simple substitute for functools.wraps."""
    for replace in ['__module__', '__name__', '__qualname__', '__doc__']:
        setattr(new, replace, getattr(old, replace))
    new.__dict__.update(old.__dict__)


code_type = type(_wrap.__code__)

# Finder/loader utility code ##################################################

def set_package(fxn):
    """Set __package__ on the returned module."""
    def set_package_wrapper(*args, **kwargs):
        module = fxn(*args, **kwargs)
        if not hasattr(module, '__package__') or module.__package__ is None:
            module.__package__ = module.__name__
            if not hasattr(module, '__path__'):
                module.__package__ = module.__package__.rpartition('.')[0]
        return module
    _wrap(set_package_wrapper, fxn)
    return set_package_wrapper


def set_loader(fxn):
    """Set __loader__ on the returned module."""
    def set_loader_wrapper(self, *args, **kwargs):
        module = fxn(self, *args, **kwargs)
        if not hasattr(module, '__loader__'):
            module.__loader__ = self
        return module
    _wrap(set_loader_wrapper, fxn)
    return set_loader_wrapper


def module_for_loader(fxn):
    """Decorator to handle selecting the proper module for loaders.

    The decorated function is passed the module to use instead of the module
    name. The module passed in to the function is either from sys.modules if
    it already exists or is a new module which has __name__ set and is inserted
    into sys.modules. If an exception is raised and the decorator created the
    module it is subsequently removed from sys.modules.

    The decorator assumes that the decorated function takes the module name as
    the second argument.

    """
    def module_for_loader_wrapper(self, fullname, *args, **kwargs):
        module = sys.modules.get(fullname)
        is_reload = bool(module)
        if not is_reload:
            # This must be done before open() is called as the 'io' module
            # implicitly imports 'locale' and would otherwise trigger an
            # infinite loop.
            module = imp.new_module(fullname)
            sys.modules[fullname] = module
        try:
            return fxn(self, module, *args, **kwargs)
        except:
            if not is_reload:
                del sys.modules[fullname]
            raise
    _wrap(module_for_loader_wrapper, fxn)
    return module_for_loader_wrapper


def _check_name(method):
    """Decorator to verify that the module being requested matches the one the
    loader can handle.

    The first argument (self) must define _name which the second argument is
    compared against. If the comparison fails then ImportError is raised.

    """
    def _check_name_wrapper(self, name, *args, **kwargs):
        if self._name != name:
            raise ImportError("loader cannot handle %s" % name)
        return method(self, name, *args, **kwargs)
    _wrap(_check_name_wrapper, method)
    return _check_name_wrapper


def _requires_builtin(fxn):
    """Decorator to verify the named module is built-in."""
    def _requires_builtin_wrapper(self, fullname):
        if fullname not in sys.builtin_module_names:
            raise ImportError("{0} is not a built-in module".format(fullname))
        return fxn(self, fullname)
    _wrap(_requires_builtin_wrapper, fxn)
    return _requires_builtin_wrapper


def _requires_frozen(fxn):
    """Decorator to verify the named module is frozen."""
    def _requires_frozen_wrapper(self, fullname):
        if not imp.is_frozen(fullname):
            raise ImportError("{0} is not a frozen module".format(fullname))
        return fxn(self, fullname)
    _wrap(_requires_frozen_wrapper, fxn)
    return _requires_frozen_wrapper


def _suffix_list(suffix_type):
    """Return a list of file suffixes based on the imp file type."""
    return [suffix[0] for suffix in imp.get_suffixes()
            if suffix[2] == suffix_type]


# Loaders #####################################################################

class BuiltinImporter:

    """Meta path import for built-in modules.

    All methods are either class or static methods to avoid the need to
    instantiate the class.

    """

    @classmethod
    def find_module(cls, fullname, path=None):
        """Find the built-in module.

        If 'path' is ever specified then the search is considered a failure.

        """
        if path is not None:
            return None
        return cls if imp.is_builtin(fullname) else None

    @classmethod
    @set_package
    @set_loader
    @_requires_builtin
    def load_module(cls, fullname):
        """Load a built-in module."""
        is_reload = fullname in sys.modules
        try:
            return imp.init_builtin(fullname)
        except:
            if not is_reload and fullname in sys.modules:
                del sys.modules[fullname]
            raise

    @classmethod
    @_requires_builtin
    def get_code(cls, fullname):
        """Return None as built-in modules do not have code objects."""
        return None

    @classmethod
    @_requires_builtin
    def get_source(cls, fullname):
        """Return None as built-in modules do not have source code."""
        return None

    @classmethod
    @_requires_builtin
    def is_package(cls, fullname):
        """Return None as built-in modules are never packages."""
        return False


class FrozenImporter:

    """Meta path import for frozen modules.

    All methods are either class or static methods to avoid the need to
    instantiate the class.

    """

    @classmethod
    def find_module(cls, fullname, path=None):
        """Find a frozen module."""
        return cls if imp.is_frozen(fullname) else None

    @classmethod
    @set_package
    @set_loader
    @_requires_frozen
    def load_module(cls, fullname):
        """Load a frozen module."""
        is_reload = fullname in sys.modules
        try:
            return imp.init_frozen(fullname)
        except:
            if not is_reload and fullname in sys.modules:
                del sys.modules[fullname]
            raise

    @classmethod
    @_requires_frozen
    def get_code(cls, fullname):
        """Return the code object for the frozen module."""
        return imp.get_frozen_object(fullname)

    @classmethod
    @_requires_frozen
    def get_source(cls, fullname):
        """Return None as frozen modules do not have source code."""
        return None

    @classmethod
    @_requires_frozen
    def is_package(cls, fullname):
        """Return if the frozen module is a package."""
        return imp.is_frozen_package(fullname)


class _LoaderBasics:

    """Base class of common code needed by both SourceLoader and
    _SourcelessFileLoader."""

    def is_package(self, fullname):
        """Concrete implementation of InspectLoader.is_package by checking if
        the path returned by get_filename has a filename of '__init__.py'."""
        filename = self.get_filename(fullname).rpartition(path_sep)[2]
        return filename.rsplit('.', 1)[0] == '__init__'

    def _bytes_from_bytecode(self, fullname, data, source_stats):
        """Return the marshalled bytes from bytecode, verifying the magic
        number, timestamp and source size along the way.

        If source_stats is None then skip the timestamp check.

        """
        magic = data[:4]
        raw_timestamp = data[4:8]
        raw_size = data[8:12]
        if len(magic) != 4 or magic != imp.get_magic():
            raise ImportError("bad magic number in {}".format(fullname))
        elif len(raw_timestamp) != 4:
            raise EOFError("bad timestamp in {}".format(fullname))
        elif len(raw_size) != 4:
            raise EOFError("bad size in {}".format(fullname))
        if source_stats is not None:
            try:
                source_mtime = int(source_stats['mtime'])
            except KeyError:
                pass
            else:
                if _r_long(raw_timestamp) != source_mtime:
                    raise ImportError("bytecode is stale for {}".format(fullname))
            try:
                source_size = source_stats['size'] & 0xFFFFFFFF
            except KeyError:
                pass
            else:
                if _r_long(raw_size) != source_size:
                    raise ImportError("bytecode is stale for {}".format(fullname))
        # Can't return the code object as errors from marshal loading need to
        # propagate even when source is available.
        return data[12:]

    @module_for_loader
    def _load_module(self, module, *, sourceless=False):
        """Helper for load_module able to handle either source or sourceless
        loading."""
        name = module.__name__
        code_object = self.get_code(name)
        module.__file__ = self.get_filename(name)
        if not sourceless:
            module.__cached__ = imp.cache_from_source(module.__file__)
        else:
            module.__cached__ = module.__file__
        module.__package__ = name
        if self.is_package(name):
            module.__path__ = [module.__file__.rsplit(path_sep, 1)[0]]
        else:
            module.__package__ = module.__package__.rpartition('.')[0]
        module.__loader__ = self
        exec(code_object, module.__dict__)
        return module


class SourceLoader(_LoaderBasics):

    def path_mtime(self, path):
        """Optional method that returns the modification time (an int) for the
        specified path, where path is a str.
        """
        raise NotImplementedError

    def path_stats(self, path):
        """Optional method returning a metadata dict for the specified path
        to by the path (str).
        Possible keys:
        - 'mtime' (mandatory) is the numeric timestamp of last source
          code modification;
        - 'size' (optional) is the size in bytes of the source code.

        Implementing this method allows the loader to read bytecode files.
        """
        return {'mtime': self.path_mtime(path)}

    def set_data(self, path, data):
        """Optional method which writes data (bytes) to a file path (a str).

        Implementing this method allows for the writing of bytecode files.

        """
        raise NotImplementedError


    def get_source(self, fullname):
        """Concrete implementation of InspectLoader.get_source."""
        import tokenize
        path = self.get_filename(fullname)
        try:
            source_bytes = self.get_data(path)
        except IOError:
            raise ImportError("source not available through get_data()")
        encoding = tokenize.detect_encoding(_io.BytesIO(source_bytes).readline)
        newline_decoder = _io.IncrementalNewlineDecoder(None, True)
        return newline_decoder.decode(source_bytes.decode(encoding[0]))

    def get_code(self, fullname):
        """Concrete implementation of InspectLoader.get_code.

        Reading of bytecode requires path_stats to be implemented. To write
        bytecode, set_data must also be implemented.

        """
        source_path = self.get_filename(fullname)
        bytecode_path = imp.cache_from_source(source_path)
        source_mtime = None
        if bytecode_path is not None:
            try:
                st = self.path_stats(source_path)
            except NotImplementedError:
                pass
            else:
                source_mtime = int(st['mtime'])
                try:
                    data = self.get_data(bytecode_path)
                except IOError:
                    pass
                else:
                    try:
                        bytes_data = self._bytes_from_bytecode(fullname, data,
                                                               st)
                    except (ImportError, EOFError):
                        pass
                    else:
                        found = marshal.loads(bytes_data)
                        if isinstance(found, code_type):
                            imp._fix_co_filename(found, source_path)
                            return found
                        else:
                            msg = "Non-code object in {}"
                            raise ImportError(msg.format(bytecode_path))
        source_bytes = self.get_data(source_path)
        code_object = compile(source_bytes, source_path, 'exec',
                                dont_inherit=True)
        if (not sys.dont_write_bytecode and bytecode_path is not None and
                source_mtime is not None):
            # If e.g. Jython ever implements imp.cache_from_source to have
            # their own cached file format, this block of code will most likely
            # throw an exception.
            data = bytearray(imp.get_magic())
            data.extend(_w_long(source_mtime))
            data.extend(_w_long(len(source_bytes)))
            data.extend(marshal.dumps(code_object))
            try:
                self.set_data(bytecode_path, data)
            except NotImplementedError:
                pass
        return code_object

    def load_module(self, fullname):
        """Concrete implementation of Loader.load_module.

        Requires ExecutionLoader.get_filename and ResourceLoader.get_data to be
        implemented to load source code. Use of bytecode is dictated by whether
        get_code uses/writes bytecode.

        """
        return self._load_module(fullname)


class _FileLoader:

    """Base file loader class which implements the loader protocol methods that
    require file system usage."""

    def __init__(self, fullname, path):
        """Cache the module name and the path to the file found by the
        finder."""
        self._name = fullname
        self._path = path

    @_check_name
    def get_filename(self, fullname):
        """Return the path to the source file as found by the finder."""
        return self._path

    def get_data(self, path):
        """Return the data from path as raw bytes."""
        with _io.FileIO(path, 'r') as file:
            return file.read()


class _SourceFileLoader(_FileLoader, SourceLoader):

    """Concrete implementation of SourceLoader using the file system."""

    def path_stats(self, path):
        """Return the metadat for the path."""
        st = _os.stat(path)
        return {'mtime': st.st_mtime, 'size': st.st_size}

    def set_data(self, path, data):
        """Write bytes data to a file."""
        parent, _, filename = path.rpartition(path_sep)
        path_parts = []
        # Figure out what directories are missing.
        while parent and not _path_isdir(parent):
            parent, _, part = parent.rpartition(path_sep)
            path_parts.append(part)
        # Create needed directories.
        for part in reversed(path_parts):
            parent = _path_join(parent, part)
            try:
                _os.mkdir(parent)
            except FileExistsError:
                # Probably another Python process already created the dir.
                continue
            except PermissionError:
                # If can't get proper access, then just forget about writing
                # the data.
                return
        try:
            _write_atomic(path, data)
        except (PermissionError, FileExistsError):
            # Don't worry if you can't write bytecode or someone is writing
            # it at the same time.
            pass


class _SourcelessFileLoader(_FileLoader, _LoaderBasics):

    """Loader which handles sourceless file imports."""

    def load_module(self, fullname):
        return self._load_module(fullname, sourceless=True)

    def get_code(self, fullname):
        path = self.get_filename(fullname)
        data = self.get_data(path)
        bytes_data = self._bytes_from_bytecode(fullname, data, None)
        found = marshal.loads(bytes_data)
        if isinstance(found, code_type):
            return found
        else:
            raise ImportError("Non-code object in {}".format(path))

    def get_source(self, fullname):
        """Return None as there is no source code."""
        return None


class _ExtensionFileLoader:

    """Loader for extension modules.

    The constructor is designed to work with FileFinder.

    """

    def __init__(self, name, path):
        """Initialize the loader.

        If is_pkg is True then an exception is raised as extension modules
        cannot be the __init__ module for an extension module.

        """
        self._name = name
        self._path = path

    @_check_name
    @set_package
    @set_loader
    def load_module(self, fullname):
        """Load an extension module."""
        is_reload = fullname in sys.modules
        try:
            return imp.load_dynamic(fullname, self._path)
        except:
            if not is_reload and fullname in sys.modules:
                del sys.modules[fullname]
            raise

    @_check_name
    def is_package(self, fullname):
        """Return False as an extension module can never be a package."""
        return False

    @_check_name
    def get_code(self, fullname):
        """Return None as an extension module cannot create a code object."""
        return None

    @_check_name
    def get_source(self, fullname):
        """Return None as extension modules have no source code."""
        return None


# Finders #####################################################################

class PathFinder:

    """Meta path finder for sys.(path|path_hooks|path_importer_cache)."""

    @classmethod
    def _path_hooks(cls, path, hooks=None):
        """Search sequence of hooks for a finder for 'path'.

        If 'hooks' is false then use sys.path_hooks.

        """
        if not hooks:
            hooks = sys.path_hooks
        for hook in hooks:
            try:
                return hook(path)
            except ImportError:
                continue
        else:
            raise ImportError("no path hook found for {0}".format(path))

    @classmethod
    def _path_importer_cache(cls, path, default=None):
        """Get the finder for the path from sys.path_importer_cache.

        If the path is not in the cache, find the appropriate finder and cache
        it. If None is cached, get the default finder and cache that
        (if applicable).

        Because of NullImporter, some finder should be returned. The only
        explicit fail case is if None is cached but the path cannot be used for
        the default hook, for which ImportError is raised.

        """
        try:
            finder = sys.path_importer_cache[path]
        except KeyError:
            finder = cls._path_hooks(path)
            sys.path_importer_cache[path] = finder
        else:
            if finder is None and default:
                # Raises ImportError on failure.
                finder = default(path)
                sys.path_importer_cache[path] = finder
        return finder

    @classmethod
    def find_module(cls, fullname, path=None):
        """Find the module on sys.path or 'path' based on sys.path_hooks and
        sys.path_importer_cache."""
        if not path:
            path = sys.path
        for entry in path:
            try:
                finder = cls._path_importer_cache(entry)
            except ImportError:
                continue
            if finder:
                loader = finder.find_module(fullname)
                if loader:
                    return loader
        else:
            return None


class _FileFinder:

    """File-based finder.

    Constructor takes a list of objects detailing what file extensions their
    loader supports along with whether it can be used for a package.

    """

    def __init__(self, path, *details):
        """Initialize with finder details."""
        packages = []
        modules = []
        for detail in details:
            modules.extend((suffix, detail.loader) for suffix in detail.suffixes)
            if detail.supports_packages:
                packages.extend((suffix, detail.loader)
                                for suffix in detail.suffixes)
        self.packages = packages
        self.modules = modules
        self.path = path

    def find_module(self, fullname):
        """Try to find a loader for the specified module."""
        tail_module = fullname.rpartition('.')[2]
        base_path = _path_join(self.path, tail_module)
        if _path_isdir(base_path) and _case_ok(self.path, tail_module):
            for suffix, loader in self.packages:
                init_filename = '__init__' + suffix
                full_path = _path_join(base_path, init_filename)
                if (_path_isfile(full_path) and
                        _case_ok(base_path, init_filename)):
                    return loader(fullname, full_path)
            else:
                msg = "Not importing directory {}: missing __init__"
                _warnings.warn(msg.format(base_path), ImportWarning)
        for suffix, loader in self.modules:
            mod_filename = tail_module + suffix
            full_path = _path_join(self.path, mod_filename)
            if _path_isfile(full_path) and _case_ok(self.path, mod_filename):
                return loader(fullname, full_path)
        return None

class _SourceFinderDetails:

    loader = _SourceFileLoader
    supports_packages = True

    def __init__(self):
        self.suffixes = _suffix_list(imp.PY_SOURCE)

class _SourcelessFinderDetails:

    loader = _SourcelessFileLoader
    supports_packages = True

    def __init__(self):
        self.suffixes = _suffix_list(imp.PY_COMPILED)


class _ExtensionFinderDetails:

    loader = _ExtensionFileLoader
    supports_packages = False

    def __init__(self):
        self.suffixes = _suffix_list(imp.C_EXTENSION)


# Import itself ###############################################################

def _file_path_hook(path):
    """If the path is a directory, return a file-based finder."""
    if _path_isdir(path):
        return _FileFinder(path, _ExtensionFinderDetails(),
                           _SourceFinderDetails(),
                           _SourcelessFinderDetails())
    else:
        raise ImportError("only directories are supported")


_DEFAULT_PATH_HOOK = _file_path_hook

class _DefaultPathFinder(PathFinder):

    """Subclass of PathFinder that implements implicit semantics for
    __import__."""

    @classmethod
    def _path_hooks(cls, path):
        """Search sys.path_hooks as well as implicit path hooks."""
        try:
            return super()._path_hooks(path)
        except ImportError:
            implicit_hooks = [_DEFAULT_PATH_HOOK, imp.NullImporter]
            return super()._path_hooks(path, implicit_hooks)

    @classmethod
    def _path_importer_cache(cls, path):
        """Use the default path hook when None is stored in
        sys.path_importer_cache."""
        return super()._path_importer_cache(path, _DEFAULT_PATH_HOOK)


class _ImportLockContext:

    """Context manager for the import lock."""

    def __enter__(self):
        """Acquire the import lock."""
        imp.acquire_lock()

    def __exit__(self, exc_type, exc_value, exc_traceback):
        """Release the import lock regardless of any raised exceptions."""
        imp.release_lock()


_IMPLICIT_META_PATH = [BuiltinImporter, FrozenImporter, _DefaultPathFinder]

_ERR_MSG = 'No module named {!r}'

def _gcd_import(name, package=None, level=0):
    """Import and return the module based on its name, the package the call is
    being made from, and the level adjustment.

    This function represents the greatest common denominator of functionality
    between import_module and __import__. This includes setting __package__ if
    the loader did not.

    """
    if package:
        if not hasattr(package, 'rindex'):
            raise ValueError("__package__ not set to a string")
        elif package not in sys.modules:
            msg = ("Parent module {0!r} not loaded, cannot perform relative "
                   "import")
            raise SystemError(msg.format(package))
    if not name and level == 0:
        raise ValueError("Empty module name")
    if level > 0:
        dot = len(package)
        for x in range(level, 1, -1):
            try:
                dot = package.rindex('.', 0, dot)
            except ValueError:
                raise ValueError("attempted relative import beyond "
                                 "top-level package")
        if name:
            name = "{0}.{1}".format(package[:dot], name)
        else:
            name = package[:dot]
    with _ImportLockContext():
        try:
            module = sys.modules[name]
            if module is None:
                message = ("import of {} halted; "
                            "None in sys.modules".format(name))
                raise ImportError(message)
            return module
        except KeyError:
            pass
        parent = name.rpartition('.')[0]
        path = None
        if parent:
            if parent not in sys.modules:
                _gcd_import(parent)
            # Backwards-compatibility; be nicer to skip the dict lookup.
            parent_module = sys.modules[parent]
            try:
                path = parent_module.__path__
            except AttributeError:
                msg = (_ERR_MSG + '; {} is not a package').format(name, parent)
                raise ImportError(msg)
        meta_path = sys.meta_path + _IMPLICIT_META_PATH
        for finder in meta_path:
            loader = finder.find_module(name, path)
            if loader is not None:
                # The parent import may have already imported this module.
                if name not in sys.modules:
                    loader.load_module(name)
                break
        else:
            raise ImportError(_ERR_MSG.format(name))
        # Backwards-compatibility; be nicer to skip the dict lookup.
        module = sys.modules[name]
        if parent:
            # Set the module as an attribute on its parent.
            setattr(parent_module, name.rpartition('.')[2], module)
        # Set __package__ if the loader did not.
        if not hasattr(module, '__package__') or module.__package__ is None:
            # Watch out for what comes out of sys.modules to not be a module,
            # e.g. an int.
            try:
                module.__package__ = module.__name__
                if not hasattr(module, '__path__'):
                    module.__package__ = module.__package__.rpartition('.')[0]
            except AttributeError:
                pass
        return module


def __import__(name, globals={}, locals={}, fromlist=[], level=0):
    """Import a module.

    The 'globals' argument is used to infer where the import is occuring from
    to handle relative imports. The 'locals' argument is ignored. The
    'fromlist' argument specifies what should exist as attributes on the module
    being imported (e.g. ``from module import <fromlist>``).  The 'level'
    argument represents the package location to import from in a relative
    import (e.g. ``from ..pkg import mod`` would have a 'level' of 2).

    """
    if not hasattr(name, 'rpartition'):
        raise TypeError("module name must be str, not {}".format(type(name)))
    if level == 0:
        module = _gcd_import(name)
    else:
        # __package__ is not guaranteed to be defined or could be set to None
        # to represent that its proper value is unknown
        package = globals.get('__package__')
        if package is None:
            package = globals['__name__']
            if '__path__' not in globals:
                package = package.rpartition('.')[0]
        module = _gcd_import(name, package, level)
    # The hell that is fromlist ...
    if not fromlist:
        # Return up to the first dot in 'name'. This is complicated by the fact
        # that 'name' may be relative.
        if level == 0:
            return sys.modules[name.partition('.')[0]]
        elif not name:
            return module
        else:
            cut_off = len(name) - len(name.partition('.')[0])
            return sys.modules[module.__name__[:-cut_off]]
    else:
        # If a package was imported, try to import stuff from fromlist.
        if hasattr(module, '__path__'):
            if '*' in fromlist and hasattr(module, '__all__'):
                fromlist = list(fromlist)
                fromlist.remove('*')
                fromlist.extend(module.__all__)
            for x in (y for y in fromlist if not hasattr(module,y)):
                try:
                    _gcd_import('{0}.{1}'.format(module.__name__, x))
                except ImportError:
                    pass
        return module
Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for ProjectModifiedEvent.java.
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
Tip: Use ↑ and ↓ arrow keys to navigate and return to view the file.
Tip: You can also navigate files with Ctrl+j (next) and Ctrl+k (previous) and view the file with Ctrl+o.
Tip: You can also navigate files with Alt+j (next) and Alt+k (previous) and view the file with Alt+o.