71 lines
2.5 KiB
Python
71 lines
2.5 KiB
Python
from .named import NamedExtensionManager
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class DriverManager(NamedExtensionManager):
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"""Load a single plugin with a given name from the namespace.
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:param namespace: The namespace for the entry points.
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:type namespace: str
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:param name: The name of the driver to load.
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:type name: str
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:param invoke_on_load: Boolean controlling whether to invoke the
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object returned by the entry point after the driver is loaded.
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:type invoke_on_load: bool
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:param invoke_args: Positional arguments to pass when invoking
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the object returned by the entry point. Only used if invoke_on_load
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is True.
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:type invoke_args: tuple
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:param invoke_kwds: Named arguments to pass when invoking
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the object returned by the entry point. Only used if invoke_on_load
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is True.
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:type invoke_kwds: dict
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"""
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def __init__(self, namespace, name,
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invoke_on_load=False, invoke_args=(), invoke_kwds={}):
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super(DriverManager, self).__init__(
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namespace=namespace,
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names=[name],
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invoke_on_load=invoke_on_load,
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invoke_args=invoke_args,
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invoke_kwds=invoke_kwds,
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)
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if not self.extensions:
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raise RuntimeError('No %r driver found, looking for %r' %
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(namespace, name))
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if len(self.extensions) > 1:
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raise RuntimeError('Multiple %r drivers found: %s' %
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(namespace,
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','.join('%s:%s' % (e.module_name, e.attrs[0])
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for e in self.extensions))
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)
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def __call__(self, func, *args, **kwds):
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"""Invokes func() for the single loaded extension.
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The signature for func() should be::
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def func(ext, *args, **kwds):
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pass
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The first argument to func(), 'ext', is the
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:class:`~stevedore.extension.Extension` instance.
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Exceptions raised from within func() are logged and ignored.
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:param func: Callable to invoke for each extension.
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:param args: Variable arguments to pass to func()
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:param kwds: Keyword arguments to pass to func()
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:returns: List of values returned from func()
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"""
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results = self.map(func, *args, **kwds)
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if results:
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return results[0]
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@property
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def driver(self):
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"""Returns the driver being used by this manager.
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"""
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ext = self.extensions[0]
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return ext.obj if ext.obj else ext.plugin
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