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"""Facility to load plugins."""
import sys
import os
from importlib import import_module
from straight.plugin.manager import PluginManager
class Loader(object):
"""Base loader class. Only used as a base-class for other loaders."""
def __init__(self, *args, **kwargs):
self._cache = []
def load(self, *args, **kwargs):
self._fill_cache(*args, **kwargs)
self._post_fill()
self._order()
return PluginManager(self._cache)
def _meta(self, plugin):
meta = getattr(plugin, '__plugin__', None)
return meta
def _post_fill(self):
for plugin in self._cache:
meta = self._meta(plugin)
if not getattr(meta, 'load', True):
self._cache.remove(plugin)
for implied_namespace in getattr(meta, 'imply_plugins', []):
plugins = self._cache
self._cache = self.load(implied_namespace)
self._post_fill()
combined = []
combined.extend(plugins)
combined.extend(self._cache)
self._cache = combined
def _order(self):
self._cache.sort(key=self._plugin_priority, reverse=True)
def _plugin_priority(self, plugin):
meta = self._meta(plugin)
return getattr(meta, 'priority', 0.0)
class ModuleLoader(Loader):
"""Performs the work of locating and loading straight plugins.
This looks for plugins in every location in the import path.
"""
def __init__(self, recurse=False):
super(ModuleLoader, self).__init__()
self.recurse = recurse
def _isPackage(self, path):
pkg_init = os.path.join(path, '__init__.py')
if os.path.exists(pkg_init):
return True
return False
def _findPluginFilePaths(self, namespace):
already_seen = set()
# Look in each location in the path
for path in sys.path:
# Within this, we want to look for a package for the namespace
namespace_rel_path = namespace.replace(".", os.path.sep)
namespace_path = os.path.join(path, namespace_rel_path)
if os.path.exists(namespace_path):
for possible in os.listdir(namespace_path):
poss_path = os.path.join(namespace_path, possible)
if os.path.isdir(poss_path):
if not self._isPackage(poss_path):
continue
if self.recurse:
subns = '.'.join((namespace, possible.split('.py')[0]))
for path in self._findPluginFilePaths(subns):
yield path
base = possible
else:
base, ext = os.path.splitext(possible)
if base == '__init__' or ext != '.py':
continue
if base not in already_seen:
already_seen.add(base)
yield os.path.join(namespace, possible)
def _findPluginModules(self, namespace):
for filepath in self._findPluginFilePaths(namespace):
path_segments = list(filepath.split(os.path.sep))
path_segments = [p for p in path_segments if p]
path_segments[-1] = os.path.splitext(path_segments[-1])[0]
import_path = '.'.join(path_segments)
try:
module = import_module(import_path)
except ImportError:
#raise Exception(import_path)
module = None
if module is not None:
yield module
def _fill_cache(self, namespace):
"""Load all modules found in a namespace"""
modules = self._findPluginModules(namespace)
self._cache = list(modules)
class ObjectLoader(Loader):
"""Loads classes or objects out of modules in a namespace, based on a
provided criteria.
The load() method returns all objects exported by the module.
"""
def __init__(self, recurse=False):
self.module_loader = ModuleLoader(recurse=recurse)
def _fill_cache(self, namespace):
modules = self.module_loader.load(namespace)
objects = []
for module in modules:
for attr_name in dir(module):
if not attr_name.startswith('_'):
objects.append(getattr(module, attr_name))
self._cache = objects
return objects
class ClassLoader(ObjectLoader):
"""Loads classes out of plugin modules which are subclasses of a single
given base class.
"""
def _fill_cache(self, namespace, subclasses=None):
objects = super(ClassLoader, self)._fill_cache(namespace)
classes = []
for cls in objects:
if isinstance(cls, type):
if subclasses is None:
classes.append(cls)
elif issubclass(cls, subclasses) and cls is not subclasses:
classes.append(cls)
self._cache = classes
return classes
def unified_load(namespace, subclasses=None, recurse=False):
"""Provides a unified interface to both the module and class loaders,
finding modules by default or classes if given a ``subclasses`` parameter.
"""
if subclasses is not None:
return ClassLoader(recurse=recurse).load(namespace, subclasses=subclasses)
else:
return ModuleLoader(recurse=recurse).load(namespace)
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