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# -*- test-case-name: twisted.test.test_plugin -*-
# Copyright (c) 2005 Divmod, Inc.
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Plugin system for Twisted.
@author: Jp Calderone
@author: Glyph Lefkowitz
"""
from __future__ import absolute_import, division
import os
import sys
from zope.interface import Interface, providedBy
def _determinePickleModule():
"""
Determine which 'pickle' API module to use.
"""
try:
import cPickle
return cPickle
except ImportError:
import pickle
return pickle
pickle = _determinePickleModule()
from twisted.python.components import getAdapterFactory
from twisted.python.reflect import namedAny
from twisted.python import log
from twisted.python.modules import getModule
from twisted.python.compat import iteritems
class IPlugin(Interface):
"""
Interface that must be implemented by all plugins.
Only objects which implement this interface will be considered for return
by C{getPlugins}. To be useful, plugins should also implement some other
application-specific interface.
"""
class CachedPlugin(object):
def __init__(self, dropin, name, description, provided):
self.dropin = dropin
self.name = name
self.description = description
self.provided = provided
self.dropin.plugins.append(self)
def __repr__(self):
return '<CachedPlugin %r/%r (provides %r)>' % (
self.name, self.dropin.moduleName,
', '.join([i.__name__ for i in self.provided]))
def load(self):
return namedAny(self.dropin.moduleName + '.' + self.name)
def __conform__(self, interface, registry=None, default=None):
for providedInterface in self.provided:
if providedInterface.isOrExtends(interface):
return self.load()
if getAdapterFactory(providedInterface, interface, None) is not None:
return interface(self.load(), default)
return default
# backwards compat HOORJ
getComponent = __conform__
class CachedDropin(object):
"""
A collection of L{CachedPlugin} instances from a particular module in a
plugin package.
@type moduleName: C{str}
@ivar moduleName: The fully qualified name of the plugin module this
represents.
@type description: C{str} or C{NoneType}
@ivar description: A brief explanation of this collection of plugins
(probably the plugin module's docstring).
@type plugins: C{list}
@ivar plugins: The L{CachedPlugin} instances which were loaded from this
dropin.
"""
def __init__(self, moduleName, description):
self.moduleName = moduleName
self.description = description
self.plugins = []
def _generateCacheEntry(provider):
dropin = CachedDropin(provider.__name__,
provider.__doc__)
for k, v in iteritems(provider.__dict__):
plugin = IPlugin(v, None)
if plugin is not None:
# Instantiated for its side-effects.
CachedPlugin(dropin, k, v.__doc__, list(providedBy(plugin)))
return dropin
try:
fromkeys = dict.fromkeys
except AttributeError:
def fromkeys(keys, value=None):
d = {}
for k in keys:
d[k] = value
return d
def getCache(module):
"""
Compute all the possible loadable plugins, while loading as few as
possible and hitting the filesystem as little as possible.
@param module: a Python module object. This represents a package to search
for plugins.
@return: a dictionary mapping module names to L{CachedDropin} instances.
"""
allCachesCombined = {}
mod = getModule(module.__name__)
# don't want to walk deep, only immediate children.
buckets = {}
# Fill buckets with modules by related entry on the given package's
# __path__. There's an abstraction inversion going on here, because this
# information is already represented internally in twisted.python.modules,
# but it's simple enough that I'm willing to live with it. If anyone else
# wants to fix up this iteration so that it's one path segment at a time,
# be my guest. --glyph
for plugmod in mod.iterModules():
fpp = plugmod.filePath.parent()
if fpp not in buckets:
buckets[fpp] = []
bucket = buckets[fpp]
bucket.append(plugmod)
for pseudoPackagePath, bucket in iteritems(buckets):
dropinPath = pseudoPackagePath.child('dropin.cache')
try:
lastCached = dropinPath.getModificationTime()
with dropinPath.open('r') as f:
dropinDotCache = pickle.load(f)
except:
dropinDotCache = {}
lastCached = 0
needsWrite = False
existingKeys = {}
for pluginModule in bucket:
pluginKey = pluginModule.name.split('.')[-1]
existingKeys[pluginKey] = True
if ((pluginKey not in dropinDotCache) or
(pluginModule.filePath.getModificationTime() >= lastCached)):
needsWrite = True
try:
provider = pluginModule.load()
except:
# dropinDotCache.pop(pluginKey, None)
log.err()
else:
entry = _generateCacheEntry(provider)
dropinDotCache[pluginKey] = entry
# Make sure that the cache doesn't contain any stale plugins.
for pluginKey in list(dropinDotCache.keys()):
if pluginKey not in existingKeys:
del dropinDotCache[pluginKey]
needsWrite = True
if needsWrite:
try:
dropinPath.setContent(pickle.dumps(dropinDotCache))
except OSError as e:
log.msg(
format=(
"Unable to write to plugin cache %(path)s: error "
"number %(errno)d"),
path=dropinPath.path, errno=e.errno)
except:
log.err(None, "Unexpected error while writing cache file")
allCachesCombined.update(dropinDotCache)
return allCachesCombined
def getPlugins(interface, package=None):
"""
Retrieve all plugins implementing the given interface beneath the given module.
@param interface: An interface class. Only plugins which implement this
interface will be returned.
@param package: A package beneath which plugins are installed. For
most uses, the default value is correct.
@return: An iterator of plugins.
"""
if package is None:
import twisted.plugins as package
allDropins = getCache(package)
for key, dropin in iteritems(allDropins):
for plugin in dropin.plugins:
try:
adapted = interface(plugin, None)
except:
log.err()
else:
if adapted is not None:
yield adapted
# Old, backwards compatible name. Don't use this.
getPlugIns = getPlugins
def pluginPackagePaths(name):
"""
Return a list of additional directories which should be searched for
modules to be included as part of the named plugin package.
@type name: C{str}
@param name: The fully-qualified Python name of a plugin package, eg
C{'twisted.plugins'}.
@rtype: C{list} of C{str}
@return: The absolute paths to other directories which may contain plugin
modules for the named plugin package.
"""
package = name.split('.')
# Note that this may include directories which do not exist. It may be
# preferable to remove such directories at this point, rather than allow
# them to be searched later on.
#
# Note as well that only '__init__.py' will be considered to make a
# directory a package (and thus exclude it from this list). This means
# that if you create a master plugin package which has some other kind of
# __init__ (eg, __init__.pyc) it will be incorrectly treated as a
# supplementary plugin directory.
return [
os.path.abspath(os.path.join(x, *package))
for x
in sys.path
if
not os.path.exists(os.path.join(x, *package + ['__init__.py']))]
__all__ = ['getPlugins', 'pluginPackagePaths']
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