1
# Copyright (C) 2006, 2008 Canonical Ltd
3
# This program is free software; you can redistribute it and/or modify
4
# it under the terms of the GNU General Public License as published by
5
# the Free Software Foundation; either version 2 of the License, or
6
# (at your option) any later version.
8
# This program is distributed in the hope that it will be useful,
9
# but WITHOUT ANY WARRANTY; without even the implied warranty of
10
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11
# GNU General Public License for more details.
13
# You should have received a copy of the GNU General Public License
14
# along with this program; if not, write to the Free Software
15
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17
"""Classes to provide name-to-object registry-like support."""
20
class _ObjectGetter(object):
21
"""Maintain a reference to an object, and return the object on request.
23
This is used by Registry to make plain objects function similarly
24
to lazily imported objects.
26
Objects can be any sort of python object (class, function, module,
32
def __init__(self, obj):
36
"""Get the object that was saved at creation time"""
40
class _LazyObjectGetter(_ObjectGetter):
41
"""Keep a record of a possible object.
43
When requested, load and return it.
46
__slots__ = ['_module_name', '_member_name', '_imported']
48
def __init__(self, module_name, member_name):
49
self._module_name = module_name
50
self._member_name = member_name
51
self._imported = False
52
super(_LazyObjectGetter, self).__init__(None)
55
"""Get the referenced object.
57
Upon first request, the object will be imported. Future requests will
58
return the imported object.
60
if not self._imported:
62
return super(_LazyObjectGetter, self).get_obj()
66
segments = self._member_name.split('.')
69
names = [self._member_name]
70
obj = __import__(self._module_name, globals(), locals(), names)
72
for segment in segments:
73
obj = getattr(obj, segment)
78
return "<%s.%s object at %x, module=%r attribute=%r>" % (
79
self.__class__.__module__, self.__class__.__name__, id(self),
80
self._module_name, self._member_name)
83
class Registry(object):
84
"""A class that registers objects to a name.
86
There are many places that want to collect related objects and access them
87
by a key. This class is designed to allow registering the mapping from key
88
to object. It goes one step further, and allows registering a name to a
89
hypothetical object which has not been imported yet. It also supports
90
adding additional information at registration time so that decisions can be
91
made without having to import the object (which may be expensive).
93
The functions 'get', 'get_info', and 'get_help' also support a
94
'default_key' (settable through my_registry.default_key = XXX, XXX must
95
already be registered.) Calling my_registry.get() or my_registry.get(None),
96
will return the entry for the default key.
100
"""Create a new Registry."""
101
self._default_key = None
102
# Map from key => (is_lazy, info)
107
def register(self, key, obj, help=None, info=None,
108
override_existing=False):
109
"""Register a new object to a name.
111
:param key: This is the key to use to request the object later.
112
:param obj: The object to register.
113
:param help: Help text for this entry. This may be a string or
114
a callable. If it is a callable, it should take two
115
parameters (registry, key): this registry and the key that
116
the help was registered under.
117
:param info: More information for this entry. Registry.get_info()
118
can be used to get this information. Registry treats this as an
119
opaque storage location (it is defined by the caller).
120
:param override_existing: Raise KeyErorr if False and something has
121
already been registered for that key. If True, ignore if there
122
is an existing key (always register the new value).
124
if not override_existing:
125
if key in self._dict:
126
raise KeyError('Key %r already registered' % key)
127
self._dict[key] = _ObjectGetter(obj)
128
self._add_help_and_info(key, help=help, info=info)
130
def register_lazy(self, key, module_name, member_name,
131
help=None, info=None,
132
override_existing=False):
133
"""Register a new object to be loaded on request.
135
:param module_name: The python path to the module. Such as 'os.path'.
136
:param member_name: The member of the module to return. If empty or
137
None, get() will return the module itself.
138
:param help: Help text for this entry. This may be a string or
140
:param info: More information for this entry. Registry
141
:param override_existing: If True, replace the existing object
142
with the new one. If False, if there is already something
143
registered with the same key, raise a KeyError
145
if not override_existing:
146
if key in self._dict:
147
raise KeyError('Key %r already registered' % key)
148
self._dict[key] = _LazyObjectGetter(module_name, member_name)
149
self._add_help_and_info(key, help=help, info=info)
151
def _add_help_and_info(self, key, help=None, info=None):
152
"""Add the help and information about this key"""
153
self._help_dict[key] = help
154
self._info_dict[key] = info
156
def get(self, key=None):
157
"""Return the object register()'ed to the given key.
159
May raise ImportError if the object was registered lazily and
160
there are any problems, or AttributeError if the module does not
161
have the supplied member.
163
:param key: The key to obtain the object for. If no object has been
164
registered to that key, the object registered for self.default_key
165
will be returned instead, if it exists. Otherwise KeyError will be
167
:return: The previously registered object.
168
:raises ImportError: If the object was registered lazily, and there are
169
problems during import.
170
:raises AttributeError: If registered lazily, and the module does not
171
contain the registered member.
173
return self._dict[self._get_key_or_default(key)].get_obj()
175
def get_prefix(self, fullname):
176
"""Return an object whose key is a prefix of the supplied value.
178
:fullname: The name to find a prefix for
179
:return: a tuple of (object, remainder), where the remainder is the
180
portion of the name that did not match the key.
182
for key in self.keys():
183
if fullname.startswith(key):
184
return self.get(key), fullname[len(key):]
186
def _get_key_or_default(self, key=None):
187
"""Return either 'key' or the default key if key is None"""
190
if self.default_key is None:
191
raise KeyError('Key is None, and no default key is set')
193
return self.default_key
195
def get_help(self, key=None):
196
"""Get the help text associated with the given key"""
197
the_help = self._help_dict[self._get_key_or_default(key)]
198
if callable(the_help):
199
return the_help(self, key)
202
def get_info(self, key=None):
203
"""Get the extra information associated with the given key"""
204
return self._info_dict[self._get_key_or_default(key)]
206
def remove(self, key):
207
"""Remove a registered entry.
209
This is mostly for the test suite, but it can be used by others
213
def __contains__(self, key):
214
return key in self._dict
217
"""Get a list of registered entries"""
218
return sorted(self._dict.keys())
221
for key, getter in self._dict.iteritems():
222
yield key, getter.get_obj()
225
return sorted(self.iteritems())
227
def _set_default_key(self, key):
228
if not self._dict.has_key(key):
229
raise KeyError('No object registered under key %s.' % key)
231
self._default_key = key
233
def _get_default_key(self):
234
return self._default_key
236
default_key = property(_get_default_key, _set_default_key,
237
doc="Current value of the default key."
238
" Can be set to any existing key.")
241
class FormatRegistry(Registry):
242
"""Registry specialised for handling formats."""
244
def __init__(self, other_registry=None):
245
Registry.__init__(self)
246
self._other_registry = other_registry
248
def register_lazy(self, key, module_name, member_name,
249
help=None, info=None,
250
override_existing=False):
251
# Overridden to allow capturing registrations to two seperate
252
# registries in a single call.
253
Registry.register_lazy(self, key, module_name, member_name,
254
help=help, info=info, override_existing=override_existing)
255
if self._other_registry is not None:
256
self._other_registry.register_lazy(key, module_name, member_name,
257
help=help, info=info, override_existing=override_existing)
259
def get(self, format_string):
260
r = Registry.get(self, format_string)
added
removed
bzrlib/registry.py
