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# Copyright (C) 2006 by Canonical Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
"""Functionality to create lazy evaluation objects.
This includes waiting to import a module until it is actually used.
"""
import re
import sys
class ScopeReplacer(object):
"""A lazy object that will replace itself in the appropriate scope.
This object sits, ready to create the real object the first time it is
needed.
"""
__slots__ = ('_scope', '_factory', '_name')
def __init__(self, scope, factory, name):
"""Create a temporary object in the specified scope.
Once used, a real object will be placed in the scope.
:param scope: The scope the object should appear in
:param factory: A callable that will create the real object.
It will be passed (self, scope, name)
:param name: The variable name in the given scope.
"""
self._scope = scope
self._factory = factory
self._name = name
scope[name] = self
def _replace(self):
"""Actually replace self with other in the given scope"""
factory = object.__getattribute__(self, '_factory')
scope = object.__getattribute__(self, '_scope')
name = object.__getattribute__(self, '_name')
obj = factory(self, scope, name)
scope[name] = obj
return obj
def _cleanup(self):
"""Stop holding on to all the extra stuff"""
del self._factory
del self._scope
del self._name
def __getattribute__(self, attr):
obj = object.__getattribute__(self, '_replace')()
object.__getattribute__(self, '_cleanup')()
return getattr(obj, attr)
def __call__(self, *args, **kwargs):
obj = object.__getattribute__(self, '_replace')()
object.__getattribute__(self, '_cleanup')()
return obj(*args, **kwargs)
class ImportReplacer(ScopeReplacer):
"""This is designed to replace only a portion of an import list.
It will replace itself with a module, and then make children
entries also ImportReplacer objects.
At present, this only supports 'import foo.bar.baz' syntax.
"""
# Intentially a long semi-unique name that won't likely exist
# elsewhere. (We can't use isinstance because that accesses __class__
# which causes the __getattribute__ to trigger)
__slots__ = ('_import_replacer_children', '_member', '_module_path')
def __init__(self, scope, name, module_path, member=None, children=[]):
"""Upon request import 'module_path' as the name 'module_name'.
When imported, prepare children to also be imported.
:param scope: The scope that objects should be imported into.
Typically this is globals()
:param name: The variable name. Often this is the same as the
module_path. 'bzrlib'
:param module_path: A list for the fully specified module path
['bzrlib', 'foo', 'bar']
:param member: The member inside the module to import, often this is
None, indicating the module is being imported.
:param children: Children entries to be imported later.
This should be a list of children specifications.
[('foo', 'bzrlib.foo', [('bar', 'bzrlib.foo.bar'),])]
Examples:
import foo => name='foo' module_path='foo',
member=None, children=[]
import foo.bar => name='foo' module_path='foo', member=None,
children=[('bar', ['foo', 'bar'], [])]
from foo import bar => name='bar' module_path='foo', member='bar'
children=[]
from foo import bar, baz would get translated into 2 import
requests. On for 'name=bar' and one for 'name=baz'
"""
if member is not None:
assert not children, \
'Cannot supply both a member and children'
self._import_replacer_children = children
self._member = member
self._module_path = module_path
# Indirecting through __class__ so that children can
# override _import (especially our instrumented version)
cls = object.__getattribute__(self, '__class__')
ScopeReplacer.__init__(self, scope=scope, name=name,
factory=cls._import)
def _import(self, scope, name):
children = object.__getattribute__(self, '_import_replacer_children')
member = object.__getattribute__(self, '_member')
module_path = object.__getattribute__(self, '_module_path')
module_python_path = '.'.join(module_path)
if member is not None:
module = __import__(module_python_path, scope, scope, [member])
return getattr(module, member)
else:
module = __import__(module_python_path, scope, scope, [])
for path in module_path[1:]:
module = getattr(module, path)
# Prepare the children to be imported
for child_name, child_path, grandchildren in children:
# Using self.__class__, so that children get children classes
# instantiated. (This helps with instrumented tests)
cls = object.__getattribute__(self, '__class__')
cls(module.__dict__, name=child_name,
module_path=child_path, member=None,
children=grandchildren)
return module
def _convert_import_str_to_map(import_str, imports):
"""This converts a import string into an import map.
This only understands 'import foo, foo.bar, foo.bar.baz as bing'
:param import_str: The import string to process
:param imports: The current map of all imports
"""
assert import_str.startswith('import ')
import_str = import_str[len('import '):]
for path in import_str.split(','):
path = path.strip()
as_hunks = path.split(' as ')
if len(as_hunks) == 2:
# We have 'as' so this is a different style of import
# 'import foo.bar.baz as bing' creates a local variable
# named 'bing' which points to 'foo.bar.baz'
name = as_hunks[1].strip()
module_path = as_hunks[0].strip().split('.')
assert name not in imports
# No children available in 'import foo as bar'
imports[name] = (module_path, None, {})
else:
# Now we need to handle
module_path = path.split('.')
name = module_path[0]
if name not in imports:
# This is a new import that we haven't seen before
module_def = ([name], None, {})
imports[name] = module_def
else:
module_def = imports[name]
cur_path = [name]
cur = module_def[2]
for child in module_path[1:]:
cur_path.append(child)
if child in cur:
cur = cur[child]
else:
next = (cur_path[:], None, {})
cur[child] = next
cur = next[2]
def _convert_from_str_to_map(from_str, imports):
"""This converts a 'from foo import bar' string into an import map.
:param from_str: The import string to process
:param imports: The current map of all imports
"""
assert from_str.startswith('from ')
from_str = from_str[len('from '):]
from_module, import_list = from_str.split(' import ')
from_module_path = from_module.split('.')
for path in import_list.split(','):
path = path.strip()
as_hunks = path.split(' as ')
if len(as_hunks) == 2:
# We have 'as' so this is a different style of import
# 'import foo.bar.baz as bing' creates a local variable
# named 'bing' which points to 'foo.bar.baz'
name = as_hunks[1].strip()
module = as_hunks[0].strip()
else:
name = module = path
assert name not in imports
imports[name] = (from_module_path, module, {})
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