Source code for apptools.naming.context
# (C) Copyright 2005-2022 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!
""" The base class for all naming contexts. """
# Enthought library imports.
from traits.api import Any, Dict, Event, HasTraits
from traits.api import Property, Str
# Local imports.
from .binding import Binding
from .exception import InvalidNameError, NameAlreadyBoundError
from .exception import NameNotFoundError, NotContextError
from .naming_event import NamingEvent
from .naming_manager import naming_manager
from .unique_name import make_unique_name
# Constants for environment property keys.
INITIAL_CONTEXT_FACTORY = "apptools.naming.factory.initial"
OBJECT_FACTORIES = "apptools.naming.factory.object"
STATE_FACTORIES = "apptools.naming.factory.state"
# The default environment.
ENVIRONMENT = {
# 'Context' properties.
OBJECT_FACTORIES: [],
STATE_FACTORIES: [],
}
[docs]class Context(HasTraits):
""" The base class for all naming contexts. """
# Keys for environment properties.
INITIAL_CONTEXT_FACTORY = INITIAL_CONTEXT_FACTORY
OBJECT_FACTORIES = OBJECT_FACTORIES
STATE_FACTORIES = STATE_FACTORIES
#### 'Context' interface ##################################################
# The naming environment in effect for this context.
environment = Dict(ENVIRONMENT)
# The name of the context within its own namespace.
namespace_name = Property(Str)
#### Events ####
# Fired when an object has been added to the context (either via 'bind' or
# 'create_subcontext').
object_added = Event(NamingEvent)
# Fired when an object has been changed (via 'rebind').
object_changed = Event(NamingEvent)
# Fired when an object has been removed from the context (either via
# 'unbind' or 'destroy_subcontext').
object_removed = Event(NamingEvent)
# Fired when an object in the context has been renamed (via 'rename').
object_renamed = Event(NamingEvent)
# Fired when the contents of the context have changed dramatically.
context_changed = Event(NamingEvent)
#### Protected 'Context' interface #######################################
# The bindings in the context.
_bindings = Dict(Str, Any)
###########################################################################
# 'Context' interface.
###########################################################################
#### Properties ###########################################################
def _get_namespace_name(self):
"""
Return the name of the context within its own namespace.
That is the full-path, through the namespace this context participates
in, to get to this context. For example, if the root context of the
namespace was called 'Foo', and there was a subcontext of that called
'Bar', and we were within that and called 'Baz', then this should
return 'Foo/Bar/Baz'.
"""
# FIXME: We'd like to raise an exception and force implementors to
# decide what to do. However, it appears to be pretty common that
# most Context implementations do not override this method -- possibly
# because the comments aren't clear on what this is supposed to be?
#
# Anyway, if we raise an exception then it is impossible to use any
# evaluations when building a Traits UI for a Context. That is, the
# Traits UI can't include items that have a 'visible_when' or
# 'enabled_when' evaluation. This is because the Traits evaluation
# code calls the 'get()' method on the Context which attempts to
# retrieve the current namespace_name value.
# raise OperationNotSupportedError()
return ""
#### Methods ##############################################################
[docs] def bind(self, name, obj, make_contexts=False):
"""Binds a name to an object.
If 'make_contexts' is True then any missing intermediate contexts are
created automatically.
"""
if len(name) == 0:
raise InvalidNameError("empty name")
# Parse the name.
components = self._parse_name(name)
# If there is exactly one component in the name then the operation
# takes place in this context.
if len(components) == 1:
atom = components[0]
# Is the name already bound?
if self._is_bound(atom):
raise NameAlreadyBoundError(name)
# Do the actual bind.
self._bind(atom, obj)
# Trait event notification.
self.object_added = NamingEvent(
new_binding=Binding(name=name, obj=obj, context=self)
)
# Otherwise, attempt to continue resolution into the next context.
else:
if not self._is_bound(components[0]):
if make_contexts:
self._create_subcontext(components[0])
else:
raise NameNotFoundError(components[0])
next_context = self._get_next_context(components[0])
next_context.bind("/".join(components[1:]), obj, make_contexts)
[docs] def rebind(self, name, obj, make_contexts=False):
"""Binds an object to a name that may already be bound.
If 'make_contexts' is True then any missing intermediate contexts are
created automatically.
The object may be a different object but may also be the same object
that is already bound to the specified name. The name may or may not be
already used. Think of this as a safer version of 'bind' since this
one will never raise an exception regarding a name being used.
"""
if len(name) == 0:
raise InvalidNameError("empty name")
# Parse the name.
components = self._parse_name(name)
# If there is exactly one component in the name then the operation
# takes place in this context.
if len(components) == 1:
# Do the actual rebind.
self._rebind(components[0], obj)
# Trait event notification.
self.object_changed = NamingEvent(
new_binding=Binding(name=name, obj=obj, context=self)
)
# Otherwise, attempt to continue resolution into the next context.
else:
if not self._is_bound(components[0]):
if make_contexts:
self._create_subcontext(components[0])
else:
raise NameNotFoundError(components[0])
next_context = self._get_next_context(components[0])
next_context.rebind("/".join(components[1:]), obj, make_contexts)
[docs] def unbind(self, name):
""" Unbinds a name. """
if len(name) == 0:
raise InvalidNameError("empty name")
# Parse the name.
components = self._parse_name(name)
# If there is exactly one component in the name then the operation
# takes place in this context.
if len(components) == 1:
atom = components[0]
if not self._is_bound(atom):
raise NameNotFoundError(name)
# Lookup the object that we are unbinding to use in the event
# notification.
obj = self._lookup(atom)
# Do the actual unbind.
self._unbind(atom)
# Trait event notification.
self.object_removed = NamingEvent(
old_binding=Binding(name=name, obj=obj, context=self)
)
# Otherwise, attempt to continue resolution into the next context.
else:
if not self._is_bound(components[0]):
raise NameNotFoundError(components[0])
next_context = self._get_next_context(components[0])
next_context.unbind("/".join(components[1:]))
[docs] def rename(self, old_name, new_name):
""" Binds a new name to an object. """
if len(old_name) == 0 or len(new_name) == 0:
raise InvalidNameError("empty name")
# Parse the names.
old_components = self._parse_name(old_name)
new_components = self._parse_name(new_name)
# If there is axactly one component in BOTH names then the operation
# takes place ENTIRELY in this context.
if len(old_components) == 1 and len(new_components) == 1:
# Is the old name actually bound?
if not self._is_bound(old_name):
raise NameNotFoundError(old_name)
# Is the new name already bound?
if self._is_bound(new_name):
raise NameAlreadyBoundError(new_name)
# Do the actual rename.
self._rename(old_name, new_name)
# Lookup the object that we are renaming to use in the event
# notification.
obj = self._lookup(new_name)
# Trait event notification.
self.object_renamed = NamingEvent(
old_binding=Binding(name=old_name, obj=obj, context=self),
new_binding=Binding(name=new_name, obj=obj, context=self),
)
else:
# fixme: This really needs to be transactional in case the bind
# succeeds but the unbind fails. To be safe should we just not
# support cross-context renaming for now?!?!
#
# Lookup the object.
obj = self.lookup(old_name)
# Bind the new name.
self.bind(new_name, obj)
# Unbind the old one.
self.unbind(old_name)
[docs] def lookup(self, name):
""" Resolves a name relative to this context. """
# If the name is empty we return the context itself.
if len(name) == 0:
# fixme: The JNDI spec. says that this should return a COPY of
# the context.
return self
# Parse the name.
components = self._parse_name(name)
# If there is exactly one component in the name then the operation
# takes place in this context.
if len(components) == 1:
atom = components[0]
if not self._is_bound(atom):
raise NameNotFoundError(name)
# Do the actual lookup.
obj = self._lookup(atom)
# Otherwise, attempt to continue resolution into the next context.
else:
if not self._is_bound(components[0]):
raise NameNotFoundError(components[0])
next_context = self._get_next_context(components[0])
obj = next_context.lookup("/".join(components[1:]))
return obj
# fixme: Non-JNDI
[docs] def lookup_binding(self, name):
""" Looks up the binding for a name relative to this context. """
if len(name) == 0:
raise InvalidNameError("empty name")
# Parse the name.
components = self._parse_name(name)
# If there is exactly one component in the name then the operation
# takes place in this context.
if len(components) == 1:
atom = components[0]
if not self._is_bound(atom):
raise NameNotFoundError(name)
# Do the actual lookup.
binding = self._lookup_binding(atom)
# Otherwise, attempt to continue resolution into the next context.
else:
if not self._is_bound(components[0]):
raise NameNotFoundError(components[0])
next_context = self._get_next_context(components[0])
binding = next_context.lookup_binding("/".join(components[1:]))
return binding
# fixme: Non-JNDI
[docs] def lookup_context(self, name):
"""Resolves a name relative to this context.
The name MUST resolve to a context.
"""
# If the name is empty we return the context itself.
if len(name) == 0:
# fixme: The JNDI spec. says that this should return a COPY of
# the context.
return self
# Parse the name.
components = self._parse_name(name)
# If there is exactly one component in the name then the operation
# takes place in this context.
if len(components) == 1:
atom = components[0]
if not self._is_bound(atom):
raise NameNotFoundError(name)
# Do the actual lookup.
obj = self._get_next_context(atom)
# Otherwise, attempt to continue resolution into the next context.
else:
if not self._is_bound(components[0]):
raise NameNotFoundError(components[0])
next_context = self._get_next_context(components[0])
obj = next_context.lookup("/".join(components[1:]))
return obj
[docs] def create_subcontext(self, name):
""" Creates a sub-context. """
if len(name) == 0:
raise InvalidNameError("empty name")
# Parse the name.
components = self._parse_name(name)
# If there is exactly one component in the name then the operation
# takes place in this context.
if len(components) == 1:
atom = components[0]
# Is the name already bound?
if self._is_bound(atom):
raise NameAlreadyBoundError(name)
# Do the actual creation of the sub-context.
sub = self._create_subcontext(atom)
# Trait event notification.
self.object_added = NamingEvent(
new_binding=Binding(name=name, obj=sub, context=self)
)
# Otherwise, attempt to continue resolution into the next context.
else:
if not self._is_bound(components[0]):
raise NameNotFoundError(components[0])
next_context = self._get_next_context(components[0])
sub = next_context.create_subcontext("/".join(components[1:]))
return sub
[docs] def destroy_subcontext(self, name):
""" Destroys a sub-context. """
if len(name) == 0:
raise InvalidNameError("empty name")
# Parse the name.
components = self._parse_name(name)
# If there is exactly one component in the name then the operation
# takes place in this context.
if len(components) == 1:
atom = components[0]
if not self._is_bound(atom):
raise NameNotFoundError(name)
obj = self._lookup(atom)
if not self._is_context(atom):
raise NotContextError(name)
# Do the actual destruction of the sub-context.
self._destroy_subcontext(atom)
# Trait event notification.
self.object_removed = NamingEvent(
old_binding=Binding(name=name, obj=obj, context=self)
)
# Otherwise, attempt to continue resolution into the next context.
else:
if not self._is_bound(components[0]):
raise NameNotFoundError(components[0])
next_context = self._get_next_context(components[0])
next_context.destroy_subcontext("/".join(components[1:]))
# fixme: Non-JNDI
[docs] def get_unique_name(self, prefix):
"""Returns a name that is unique within the context.
The name returned will start with the specified prefix.
"""
return make_unique_name(
prefix, existing=self.list_names(""), format="%s (%d)"
)
[docs] def list_names(self, name=""):
""" Lists the names bound in a context. """
# If the name is empty then the operation takes place in this context.
if len(name) == 0:
names = self._list_names()
# Otherwise, attempt to continue resolution into the next context.
else:
# Parse the name.
components = self._parse_name(name)
if not self._is_bound(components[0]):
raise NameNotFoundError(components[0])
next_context = self._get_next_context(components[0])
names = next_context.list_names("/".join(components[1:]))
return names
[docs] def list_bindings(self, name=""):
""" Lists the bindings in a context. """
# If the name is empty then the operation takes place in this context.
if len(name) == 0:
bindings = self._list_bindings()
# Otherwise, attempt to continue resolution into the next context.
else:
# Parse the name.
components = self._parse_name(name)
if not self._is_bound(components[0]):
raise NameNotFoundError(components[0])
next_context = self._get_next_context(components[0])
bindings = next_context.list_bindings("/".join(components[1:]))
return bindings
# fixme: Non-JNDI
[docs] def is_context(self, name):
""" Returns True if the name is bound to a context. """
# If the name is empty then it refers to this context.
if len(name) == 0:
is_context = True
else:
# Parse the name.
components = self._parse_name(name)
# If there is exactly one component in the name then the operation
# takes place in this context.
if len(components) == 1:
atom = components[0]
if not self._is_bound(atom):
raise NameNotFoundError(name)
# Do the actual check.
is_context = self._is_context(atom)
# Otherwise, attempt to continue resolution into the next context.
else:
if not self._is_bound(components[0]):
raise NameNotFoundError(components[0])
next_context = self._get_next_context(components[0])
is_context = next_context.is_context("/".join(components[1:]))
return is_context
# fixme: Non-JNDI
[docs] def search(self, obj):
""" Returns a list of namespace names that are bound to obj. """
# don't look for None
if obj is None:
return []
# Obj is bound to these names relative to this context
names = []
# path contain the name components down to the current context
path = []
self._search(obj, names, path, {})
return names
###########################################################################
# Protected 'Context' interface.
###########################################################################
def _parse_name(self, name):
"""Parse a name into a list of components.
e.g. 'foo/bar/baz' -> ['foo', 'bar', 'baz']
"""
return name.split("/")
def _is_bound(self, name):
""" Is a name bound in this context? """
return name in self._bindings
def _lookup(self, name):
""" Looks up a name in this context. """
obj = self._bindings[name]
return naming_manager.get_object_instance(obj, name, self)
def _lookup_binding(self, name):
""" Looks up the binding for a name in this context. """
return Binding(name=name, obj=self._lookup(name), context=self)
def _bind(self, name, obj):
""" Binds a name to an object in this context. """
state = naming_manager.get_state_to_bind(obj, name, self)
self._bindings[name] = state
def _rebind(self, name, obj):
""" Rebinds a name to an object in this context. """
self._bind(name, obj)
def _unbind(self, name):
""" Unbinds a name from this context. """
del self._bindings[name]
def _rename(self, old_name, new_name):
""" Renames an object in this context. """
# Bind the new name.
self._bindings[new_name] = self._bindings[old_name]
# Unbind the old one.
del self._bindings[old_name]
def _create_subcontext(self, name):
""" Creates a sub-context of this context. """
sub = self.__class__(environment=self.environment)
self._bindings[name] = sub
return sub
def _destroy_subcontext(self, name):
""" Destroys a sub-context of this context. """
del self._bindings[name]
def _list_bindings(self):
""" Lists the bindings in this context. """
bindings = []
for name in self._list_names():
bindings.append(
Binding(name=name, obj=self._lookup(name), context=self)
)
return bindings
def _list_names(self):
""" Lists the names bound in this context. """
return list(self._bindings.keys())
def _is_context(self, name):
""" Returns True if a name is bound to a context. """
return self._get_next_context(name) is not None
def _get_next_context(self, name):
""" Returns the next context. """
obj = self._lookup(name)
# If the object is a context then everything is just dandy.
if isinstance(obj, Context):
next_context = obj
else:
raise NotContextError(name)
return next_context
def _search(self, obj, names, path, searched):
"""Append to names any name bound to obj.
Join path and name with '/' to for a complete name from the
top context.
"""
# Check the bindings recursively.
for binding in self.list_bindings():
if binding.obj is obj:
path.append(binding.name)
names.append("/".join(path))
path.pop()
if (
isinstance(binding.obj, Context)
and binding.obj not in searched
):
path.append(binding.name)
searched[binding.obj] = True
binding.obj._search(obj, names, path, searched)
path.pop()
