summaryrefslogtreecommitdiffstats
path: root/Lib/ihooks.py
blob: 14a20a6020f41378a623fcea6f1bf951999a5d34 (plain)
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
"""Import hook support.

Consistent use of this module will make it possible to change the
different mechanisms involved in loading modules independently.

While the built-in module imp exports interfaces to the built-in
module searching and loading algorithm, and it is possible to replace
the built-in function __import__ in order to change the semantics of
the import statement, until now it has been difficult to combine the
effect of different __import__ hacks, like loading modules from URLs
by rimport.py.

This module defines three new concepts:

1) A "file system hooks" class provides an interface to a filesystem.

One hooks class is defined (Hooks), which uses the interface provided
by standard modules os and os.path.  It should be used as the base
class for other hooks classes.

2) A "module loader" class provides an interface to search for a
module in a search path and to load it.  It defines a method which
searches for a module in a single directory; by overriding this method
one can redefine the details of the search.  If the directory is None,
built-in and frozen modules are searched instead.

Two module loader class are defined, both implementing the search
strategy used by the built-in __import__ function: ModuleLoader uses
the imp module's find_module interface, while HookableModuleLoader
uses a file system hooks class to interact with the file system.  Both
use the imp module's load_* interfaces to actually load the module.

3) A "module importer" class provides an interface to import a
module, as well as interfaces to reload and unload a module.  It also
provides interfaces to install and uninstall itself instead of the
default __import__ and reload (and unload) functions.

One module importer class is defined (ModuleImporter), which uses a
module loader instance passed in (by default HookableModuleLoader is
instantiated).

The classes defined here should be used as base classes for extended
functionality along those lines.

If a module importer class supports dotted names, its import_module()
must return a different value depending on whether it is called on
behalf of a "from ... import ..." statement or not.  (This is caused
by the way the __import__ hook is used by the Python interpreter.)
"""


import __builtin__
import imp
import os
import sys

__all__ = ["BasicModuleLoader","Hooks","ModuleLoader","FancyModuleLoader",
           "BasicModuleImporter","ModuleImporter","install","uninstall"]

VERBOSE = 0


from imp import C_EXTENSION, PY_SOURCE, PY_COMPILED
from imp import C_BUILTIN, PY_FROZEN, PKG_DIRECTORY
BUILTIN_MODULE = C_BUILTIN
FROZEN_MODULE = PY_FROZEN


class _Verbose:

    def __init__(self, verbose = VERBOSE):
        self.verbose = verbose

    def get_verbose(self):
        return self.verbose

    def set_verbose(self, verbose):
        self.verbose = verbose

    # XXX The following is an experimental interface

    def note(self, *args):
        if self.verbose:
            self.message(*args)

    def message(self, format, *args):
        if args:
            print(format%args)
        else:
            print(format)


class BasicModuleLoader(_Verbose):

    """Basic module loader.

    This provides the same functionality as built-in import.  It
    doesn't deal with checking sys.modules -- all it provides is
    find_module() and a load_module(), as well as find_module_in_dir()
    which searches just one directory, and can be overridden by a
    derived class to change the module search algorithm when the basic
    dependency on sys.path is unchanged.

    The interface is a little more convenient than imp's:
    find_module(name, [path]) returns None or 'stuff', and
    load_module(name, stuff) loads the module.

    """

    def find_module(self, name, path = None):
        if path is None:
            path = [None] + self.default_path()
        for dir in path:
            stuff = self.find_module_in_dir(name, dir)
            if stuff: return stuff
        return None

    def default_path(self):
        return sys.path

    def find_module_in_dir(self, name, dir):
        if dir is None:
            return self.find_builtin_module(name)
        else:
            try:
                return imp.find_module(name, [dir])
            except ImportError:
                return None

    def find_builtin_module(self, name):
        # XXX frozen packages?
        if imp.is_builtin(name):
            return None, '', ('', '', BUILTIN_MODULE)
        if imp.is_frozen(name):
            return None, '', ('', '', FROZEN_MODULE)
        return None

    def load_module(self, name, stuff):
        file, filename, info = stuff
        try:
            return imp.load_module(name, file, filename, info)
        finally:
            if file: file.close()


class Hooks(_Verbose):

    """Hooks into the filesystem and interpreter.

    By deriving a subclass you can redefine your filesystem interface,
    e.g. to merge it with the URL space.

    This base class behaves just like the native filesystem.

    """

    # imp interface
    def get_suffixes(self): return imp.get_suffixes()
    def new_module(self, name): return imp.new_module(name)
    def is_builtin(self, name): return imp.is_builtin(name)
    def init_builtin(self, name): return imp.init_builtin(name)
    def is_frozen(self, name): return imp.is_frozen(name)
    def init_frozen(self, name): return imp.init_frozen(name)
    def get_frozen_object(self, name): return imp.get_frozen_object(name)
    def load_source(self, name, filename, file=None):
        return imp.load_source(name, filename, file)
    def load_compiled(self, name, filename, file=None):
        return imp.load_compiled(name, filename, file)
    def load_dynamic(self, name, filename, file=None):
        return imp.load_dynamic(name, filename, file)
    def load_package(self, name, filename, file=None):
        return imp.load_module(name, file, filename, ("", "", PKG_DIRECTORY))

    def add_module(self, name):
        d = self.modules_dict()
        if name in d: return d[name]
        d[name] = m = self.new_module(name)
        return m

    # sys interface
    def modules_dict(self): return sys.modules
    def default_path(self): return sys.path

    def path_split(self, x): return os.path.split(x)
    def path_join(self, x, y): return os.path.join(x, y)
    def path_isabs(self, x): return os.path.isabs(x)
    # etc.

    def path_exists(self, x): return os.path.exists(x)
    def path_isdir(self, x): return os.path.isdir(x)
    def path_isfile(self, x): return os.path.isfile(x)
    def path_islink(self, x): return os.path.islink(x)
    # etc.

    def openfile(self, *x): return open(*x)
    openfile_error = IOError
    def listdir(self, x): return os.listdir(x)
    listdir_error = os.error
    # etc.


class ModuleLoader(BasicModuleLoader):

    """Default module loader; uses file system hooks.

    By defining suitable hooks, you might be able to load modules from
    other sources than the file system, e.g. from compressed or
    encrypted files, tar files or (if you're brave!) URLs.

    """

    def __init__(self, hooks = None, verbose = VERBOSE):
        BasicModuleLoader.__init__(self, verbose)
        self.hooks = hooks or Hooks(verbose)

    def default_path(self):
        return self.hooks.default_path()

    def modules_dict(self):
        return self.hooks.modules_dict()

    def get_hooks(self):
        return self.hooks

    def set_hooks(self, hooks):
        self.hooks = hooks

    def find_builtin_module(self, name):
        # XXX frozen packages?
        if self.hooks.is_builtin(name):
            return None, '', ('', '', BUILTIN_MODULE)
        if self.hooks.is_frozen(name):
            return None, '', ('', '', FROZEN_MODULE)
        return None

    def find_module_in_dir(self, name, dir, allow_packages=1):
        if dir is None:
            return self.find_builtin_module(name)
        if allow_packages:
            fullname = self.hooks.path_join(dir, name)
            if self.hooks.path_isdir(fullname):
                stuff = self.find_module_in_dir("__init__", fullname, 0)
                if stuff:
                    file = stuff[0]
                    if file: file.close()
                    return None, fullname, ('', '', PKG_DIRECTORY)
        for info in self.hooks.get_suffixes():
            suff, mode, type = info
            fullname = self.hooks.path_join(dir, name+suff)
            try:
                fp = self.hooks.openfile(fullname, mode)
                return fp, fullname, info
            except self.hooks.openfile_error:
                pass
        return None

    def load_module(self, name, stuff):
        file, filename, info = stuff
        (suff, mode, type) = info
        try:
            if type == BUILTIN_MODULE:
                return self.hooks.init_builtin(name)
            if type == FROZEN_MODULE:
                return self.hooks.init_frozen(name)
            if type == C_EXTENSION:
                m = self.hooks.load_dynamic(name, filename, file)
            elif type == PY_SOURCE:
                m = self.hooks.load_source(name, filename, file)
            elif type == PY_COMPILED:
                m = self.hooks.load_compiled(name, filename, file)
            elif type == PKG_DIRECTORY:
                m = self.hooks.load_package(name, filename, file)
            else:
                raise ImportError, "Unrecognized module type (%r) for %s" % \
                      (type, name)
        finally:
            if file: file.close()
        m.__file__ = filename
        return m


class FancyModuleLoader(ModuleLoader):

    """Fancy module loader -- parses and execs the code itself."""

    def load_module(self, name, stuff):
        file, filename, (suff, mode, type) = stuff
        realfilename = filename
        path = None

        if type == PKG_DIRECTORY:
            initstuff = self.find_module_in_dir("__init__", filename, 0)
            if not initstuff:
                raise ImportError, "No __init__ module in package %s" % name
            initfile, initfilename, initinfo = initstuff
            initsuff, initmode, inittype = initinfo
            if inittype not in (PY_COMPILED, PY_SOURCE):
                if initfile: initfile.close()
                raise ImportError, \
                    "Bad type (%r) for __init__ module in package %s" % (
                    inittype, name)
            path = [filename]
            file = initfile
            realfilename = initfilename
            type = inittype

        if type == FROZEN_MODULE:
            code = self.hooks.get_frozen_object(name)
        elif type == PY_COMPILED:
            import marshal
            file.seek(8)
            code = marshal.load(file)
        elif type == PY_SOURCE:
            data = file.read()
            code = compile(data, realfilename, 'exec')
        else:
            return ModuleLoader.load_module(self, name, stuff)

        m = self.hooks.add_module(name)
        if path:
            m.__path__ = path
        m.__file__ = filename
        try:
            exec(code, m.__dict__)
        except:
            d = self.hooks.modules_dict()
            if name in d:
                del d[name]
            raise
        return m


class BasicModuleImporter(_Verbose):

    """Basic module importer; uses module loader.

    This provides basic import facilities but no package imports.

    """

    def __init__(self, loader = None, verbose = VERBOSE):
        _Verbose.__init__(self, verbose)
        self.loader = loader or ModuleLoader(None, verbose)
        self.modules = self.loader.modules_dict()

    def get_loader(self):
        return self.loader

    def set_loader(self, loader):
        self.loader = loader

    def get_hooks(self):
        return self.loader.get_hooks()

    def set_hooks(self, hooks):
        return self.loader.set_hooks(hooks)

    def import_module(self, name, globals={}, locals={}, fromlist=[]):
        name = str(name)
        if name in self.modules:
            return self.modules[name] # Fast path
        stuff = self.loader.find_module(name)
        if not stuff:
            raise ImportError, "No module named %s" % name
        return self.loader.load_module(name, stuff)

    def reload(self, module, path = None):
        name = str(module.__name__)
        stuff = self.loader.find_module(name, path)
        if not stuff:
            raise ImportError, "Module %s not found for reload" % name
        return self.loader.load_module(name, stuff)

    def unload(self, module):
        del self.modules[str(module.__name__)]
        # XXX Should this try to clear the module's namespace?

    def install(self):
        self.save_import_module = __builtin__.__import__
        if not hasattr(__builtin__, 'unload'):
            __builtin__.unload = None
        self.save_unload = __builtin__.unload
        __builtin__.__import__ = self.import_module
        __builtin__.unload = self.unload

    def uninstall(self):
        __builtin__.__import__ = self.save_import_module
        __builtin__.unload = self.save_unload
        if not __builtin__.unload:
            del __builtin__.unload


class ModuleImporter(BasicModuleImporter):

    """A module importer that supports packages."""

    def import_module(self, name, globals=None, locals=None, fromlist=None):
        parent = self.determine_parent(globals)
        q, tail = self.find_head_package(parent, str(name))
        m = self.load_tail(q, tail)
        if not fromlist:
            return q
        if hasattr(m, "__path__"):
            self.ensure_fromlist(m, fromlist)
        return m

    def determine_parent(self, globals):
        if not globals or not "__name__" in globals:
            return None
        pname = globals['__name__']
        if "__path__" in globals:
            parent = self.modules[pname]
            assert globals is parent.__dict__
            return parent
        if '.' in pname:
            i = pname.rfind('.')
            pname = pname[:i]
            parent = self.modules[pname]
            assert parent.__name__ == pname
            return parent
        return None

    def find_head_package(self, parent, name):
        if '.' in name:
            i = name.find('.')
            head = name[:i]
            tail = name[i+1:]
        else:
            head = name
            tail = ""
        if parent:
            qname = "%s.%s" % (parent.__name__, head)
        else:
            qname = head
        q = self.import_it(head, qname, parent)
        if q: return q, tail
        if parent:
            qname = head
            parent = None
            q = self.import_it(head, qname, parent)
            if q: return q, tail
        raise ImportError, "No module named " + qname

    def load_tail(self, q, tail):
        m = q
        while tail:
            i = tail.find('.')
            if i < 0: i = len(tail)
            head, tail = tail[:i], tail[i+1:]
            mname = "%s.%s" % (m.__name__, head)
            m = self.import_it(head, mname, m)
            if not m:
                raise ImportError, "No module named " + mname
        return m

    def ensure_fromlist(self, m, fromlist, recursive=0):
        for sub in fromlist:
            if sub == "*":
                if not recursive:
                    try:
                        all = m.__all__
                    except AttributeError:
                        pass
                    else:
                        self.ensure_fromlist(m, all, 1)
                continue
            if sub != "*" and not hasattr(m, sub):
                subname = "%s.%s" % (m.__name__, sub)
                submod = self.import_it(sub, subname, m)
                if not submod:
                    raise ImportError, "No module named " + subname

    def import_it(self, partname, fqname, parent, force_load=0):
        if not partname:
            raise ValueError, "Empty module name"
        if not force_load:
            try:
                return self.modules[fqname]
            except KeyError:
                pass
        try:
            path = parent and parent.__path__
        except AttributeError:
            return None
        partname = str(partname)
        stuff = self.loader.find_module(partname, path)
        if not stuff:
            return None
        fqname = str(fqname)
        m = self.loader.load_module(fqname, stuff)
        if parent:
            setattr(parent, partname, m)
        return m

    def reload(self, module):
        name = str(module.__name__)
        if '.' not in name:
            return self.import_it(name, name, None, force_load=1)
        i = name.rfind('.')
        pname = name[:i]
        parent = self.modules[pname]
        return self.import_it(name[i+1:], name, parent, force_load=1)


default_importer = None
current_importer = None

def install(importer = None):
    global current_importer
    current_importer = importer or default_importer or ModuleImporter()
    current_importer.install()

def uninstall():
    global current_importer
    current_importer.uninstall()