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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
"""
import os
import pickle
import sys
import types
from typing import Iterable, Optional, Type, TypeVar
from zope.interface import Interface, providedBy
from twisted.python import log
from twisted.python.components import getAdapterFactory
from twisted.python.modules import getModule
from twisted.python.reflect import namedAny
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:
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) -> str:
return "<CachedPlugin {!r}/{!r} (provides {!r})>".format(
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:
"""
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 L{None}
@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 provider.__dict__.items():
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 buckets.items():
dropinPath = pseudoPackagePath.child("dropin.cache")
try:
lastCached = dropinPath.getModificationTime()
with dropinPath.open("r") as f:
dropinDotCache = pickle.load(f)
except BaseException:
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 BaseException:
# 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 BaseException:
log.err(None, "Unexpected error while writing cache file")
allCachesCombined.update(dropinDotCache)
return allCachesCombined
def _pluginsPackage() -> types.ModuleType:
import twisted.plugins as package
return package
_TInterface = TypeVar("_TInterface", bound=Interface)
def getPlugins(
interface: Type[_TInterface], package: Optional[types.ModuleType] = None
) -> Iterable[_TInterface]:
"""
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:
package = _pluginsPackage()
allDropins = getCache(package)
for key, dropin in allDropins.items():
for plugin in dropin.plugins:
try:
adapted = interface(plugin, None)
except BaseException:
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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