add parent to Configurable

this adds the notion of a parent and member config,
so the config:

    c.Foo.Bar.attr = value

will only set `Bar.attr = value` for `Bar` instances
which are members of `Foo` instances.
The mechanism for doing this is

```python
f = Foo(config=cfg)
f.b = Bar(parent=f)
```

This Instance config has higher priority than plain class config for Bar,
but still lower priority than direct keyword arg trait assignment.

The main implication this has is to change the standard creation of descendants:

```python
self.bar = Bar(config=self.config)
```

into a direct parent expression

```python
self.bar = Bar(parent=self)
```

This also means that most Configurables will actually have a handle on their parent object.

IPython/config/configurable.py

@@ -1,356 +1,376 b''
 # encoding: utf-8
 """
 A base class for objects that are configurable.
 
 Inheritance diagram:
 
 .. inheritance-diagram:: IPython.config.configurable
    :parts: 3
 
 Authors:
 
 * Brian Granger
 * Fernando Perez
 * Min RK
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import datetime
 from copy import deepcopy
 
 from loader import Config
 from IPython.utils.traitlets import HasTraits, Instance
 from IPython.utils.text import indent, wrap_paragraphs
 
 
 #-----------------------------------------------------------------------------
 # Helper classes for Configurables
 #-----------------------------------------------------------------------------
 
 
 class ConfigurableError(Exception):
     pass
 
 
 class MultipleInstanceError(ConfigurableError):
     pass
 
 #-----------------------------------------------------------------------------
 # Configurable implementation
 #-----------------------------------------------------------------------------
 
 class Configurable(HasTraits):
 
     config = Instance(Config, (), {})
+    parent = Instance('IPython.config.configurable.Configurable')
     created = None
 
     def __init__(self, **kwargs):
         """Create a configurable given a config config.
 
         Parameters
         ----------
         config : Config
             If this is empty, default values are used. If config is a
             :class:`Config` instance, it will be used to configure the
             instance.
+        parent : Configurable instance
+            The parent
 
         Notes
         -----
         Subclasses of Configurable must call the :meth:`__init__` method of
         :class:`Configurable` *before* doing anything else and using
         :func:`super`::
 
             class MyConfigurable(Configurable):
                 def __init__(self, config=None):
                     super(MyConfigurable, self).__init__(config=config)
                     # Then any other code you need to finish initialization.
 
         This ensures that instances will be configured properly.
         """
+        parent = kwargs.pop('parent', None)
+        if parent:
+            # config is implied from parent
+            if 'config' not in kwargs:
+                kwargs['config'] = parent.config
+            self.parent = parent
+        
         config = kwargs.pop('config', None)
         if config is not None:
             # We used to deepcopy, but for now we are trying to just save
             # by reference.  This *could* have side effects as all components
             # will share config. In fact, I did find such a side effect in
             # _config_changed below. If a config attribute value was a mutable type
             # all instances of a component were getting the same copy, effectively
             # making that a class attribute.
             # self.config = deepcopy(config)
             self.config = config
         # This should go second so individual keyword arguments override
         # the values in config.
         super(Configurable, self).__init__(**kwargs)
         self.created = datetime.datetime.now()
 
     #-------------------------------------------------------------------------
     # Static trait notifiations
     #-------------------------------------------------------------------------
 
-    def _config_changed(self, name, old, new):
-        """Update all the class traits having ``config=True`` as metadata.
+    @classmethod
+    def section_names(cls):
+        """return section names as a list"""
+        return  [c.__name__ for c in reversed(cls.__mro__) if
+            issubclass(c, Configurable) and issubclass(cls, c)
+        ]
 
-        For any class trait with a ``config`` metadata attribute that is
-        ``True``, we update the trait with the value of the corresponding
-        config entry.
-        """
-        # Get all traits with a config metadata entry that is True
-        traits = self.traits(config=True)
+    def _load_config(self, cfg, section_names=None, traits=None):
+        """load traits from a Config object"""
 
-        # We auto-load config section for this class as well as any parent
-        # classes that are Configurable subclasses.  This starts with Configurable
-        # and works down the mro loading the config for each section.
-        section_names = [cls.__name__ for cls in \
-            reversed(self.__class__.__mro__) if
-            issubclass(cls, Configurable) and issubclass(self.__class__, cls)]
+        if traits is None:
+            traits = self.traits(config=True)
+        if section_names is None:
+            section_names = self.section_names()
 
         for sname in section_names:
             # Don't do a blind getattr as that would cause the config to
             # dynamically create the section with name self.__class__.__name__.
-            if new._has_section(sname):
-                my_config = new[sname]
+            if cfg._has_section(sname):
+                my_config = cfg[sname]
                 for k, v in traits.iteritems():
-                    # Don't allow traitlets with config=True to start with
-                    # uppercase.  Otherwise, they are confused with Config
-                    # subsections.  But, developers shouldn't have uppercase
-                    # attributes anyways! (PEP 6)
-                    if k[0].upper()==k[0] and not k.startswith('_'):
-                        raise ConfigurableError('Configurable traitlets with '
-                        'config=True must start with a lowercase so they are '
-                        'not confused with Config subsections: %s.%s' % \
-                        (self.__class__.__name__, k))
                     try:
                         # Here we grab the value from the config
                         # If k has the naming convention of a config
                         # section, it will be auto created.
                         config_value = my_config[k]
                     except KeyError:
                         pass
                     else:
-                        # print "Setting %s.%s from %s.%s=%r" % \
-                        #     (self.__class__.__name__,k,sname,k,config_value)
                         # We have to do a deepcopy here if we don't deepcopy the entire
                         # config object. If we don't, a mutable config_value will be
                         # shared by all instances, effectively making it a class attribute.
                         setattr(self, k, deepcopy(config_value))
 
+    def _config_changed(self, name, old, new):
+        """Update all the class traits having ``config=True`` as metadata.
+
+        For any class trait with a ``config`` metadata attribute that is
+        ``True``, we update the trait with the value of the corresponding
+        config entry.
+        """
+        # Get all traits with a config metadata entry that is True
+        traits = self.traits(config=True)
+
+        # We auto-load config section for this class as well as any parent
+        # classes that are Configurable subclasses.  This starts with Configurable
+        # and works down the mro loading the config for each section.
+        section_names = self.section_names()
+        self._load_config(new, traits=traits, section_names=section_names)
+        
+        # load parent config as well, if we have one
+        parent_section_names = [] if self.parent is None else self.parent.section_names()
+        for parent in parent_section_names:
+            print parent, new._has_section(parent), new[parent]
+            if not new._has_section(parent):
+                continue
+            self._load_config(new[parent], traits=traits, section_names=section_names)
+
     def update_config(self, config):
         """Fire the traits events when the config is updated."""
         # Save a copy of the current config.
         newconfig = deepcopy(self.config)
         # Merge the new config into the current one.
         newconfig.merge(config)
         # Save the combined config as self.config, which triggers the traits
         # events.
         self.config = newconfig
 
     @classmethod
     def class_get_help(cls, inst=None):
         """Get the help string for this class in ReST format.
         
         If `inst` is given, it's current trait values will be used in place of
         class defaults.
         """
         assert inst is None or isinstance(inst, cls)
-        cls_traits = cls.class_traits(config=True)
         final_help = []
         final_help.append(u'%s options' % cls.__name__)
         final_help.append(len(final_help[0])*u'-')
         for k, v in sorted(cls.class_traits(config=True).iteritems()):
             help = cls.class_get_trait_help(v, inst)
             final_help.append(help)
         return '\n'.join(final_help)
 
     @classmethod
     def class_get_trait_help(cls, trait, inst=None):
         """Get the help string for a single trait.
         
         If `inst` is given, it's current trait values will be used in place of
         the class default.
         """
         assert inst is None or isinstance(inst, cls)
         lines = []
         header = "--%s.%s=<%s>" % (cls.__name__, trait.name, trait.__class__.__name__)
         lines.append(header)
         if inst is not None:
             lines.append(indent('Current: %r' % getattr(inst, trait.name), 4))
         else:
             try:
                 dvr = repr(trait.get_default_value())
             except Exception:
                 dvr = None # ignore defaults we can't construct
             if dvr is not None:
                 if len(dvr) > 64:
                     dvr = dvr[:61]+'...'
                 lines.append(indent('Default: %s' % dvr, 4))
         if 'Enum' in trait.__class__.__name__:
             # include Enum choices
             lines.append(indent('Choices: %r' % (trait.values,)))
 
         help = trait.get_metadata('help')
         if help is not None:
             help = '\n'.join(wrap_paragraphs(help, 76))
             lines.append(indent(help, 4))
         return '\n'.join(lines)
 
     @classmethod
     def class_print_help(cls, inst=None):
         """Get the help string for a single trait and print it."""
         print cls.class_get_help(inst)
 
     @classmethod
     def class_config_section(cls):
         """Get the config class config section"""
         def c(s):
             """return a commented, wrapped block."""
             s = '\n\n'.join(wrap_paragraphs(s, 78))
 
             return '# ' + s.replace('\n', '\n# ')
 
         # section header
         breaker = '#' + '-'*78
         s = "# %s configuration" % cls.__name__
         lines = [breaker, s, breaker, '']
         # get the description trait
         desc = cls.class_traits().get('description')
         if desc:
             desc = desc.default_value
         else:
             # no description trait, use __doc__
             desc = getattr(cls, '__doc__', '')
         if desc:
             lines.append(c(desc))
             lines.append('')
 
         parents = []
         for parent in cls.mro():
             # only include parents that are not base classes
             # and are not the class itself
             # and have some configurable traits to inherit
             if parent is not cls and issubclass(parent, Configurable) and \
                     parent.class_traits(config=True):
                 parents.append(parent)
 
         if parents:
             pstr = ', '.join([ p.__name__ for p in parents ])
             lines.append(c('%s will inherit config from: %s'%(cls.__name__, pstr)))
             lines.append('')
 
         for name, trait in cls.class_traits(config=True).iteritems():
             help = trait.get_metadata('help') or ''
             lines.append(c(help))
             lines.append('# c.%s.%s = %r'%(cls.__name__, name, trait.get_default_value()))
             lines.append('')
         return '\n'.join(lines)
 
 
 
 class SingletonConfigurable(Configurable):
     """A configurable that only allows one instance.
 
     This class is for classes that should only have one instance of itself
     or *any* subclass. To create and retrieve such a class use the
     :meth:`SingletonConfigurable.instance` method.
     """
 
     _instance = None
 
     @classmethod
     def _walk_mro(cls):
         """Walk the cls.mro() for parent classes that are also singletons
 
         For use in instance()
         """
 
         for subclass in cls.mro():
             if issubclass(cls, subclass) and \
                     issubclass(subclass, SingletonConfigurable) and \
                     subclass != SingletonConfigurable:
                 yield subclass
 
     @classmethod
     def clear_instance(cls):
         """unset _instance for this class and singleton parents.
         """
         if not cls.initialized():
             return
         for subclass in cls._walk_mro():
             if isinstance(subclass._instance, cls):
                 # only clear instances that are instances
                 # of the calling class
                 subclass._instance = None
 
     @classmethod
     def instance(cls, *args, **kwargs):
         """Returns a global instance of this class.
 
         This method create a new instance if none have previously been created
         and returns a previously created instance is one already exists.
 
         The arguments and keyword arguments passed to this method are passed
         on to the :meth:`__init__` method of the class upon instantiation.
 
         Examples
         --------
 
         Create a singleton class using instance, and retrieve it::
 
             >>> from IPython.config.configurable import SingletonConfigurable
             >>> class Foo(SingletonConfigurable): pass
             >>> foo = Foo.instance()
             >>> foo == Foo.instance()
             True
 
         Create a subclass that is retrived using the base class instance::
 
             >>> class Bar(SingletonConfigurable): pass
             >>> class Bam(Bar): pass
             >>> bam = Bam.instance()
             >>> bam == Bar.instance()
             True
         """
         # Create and save the instance
         if cls._instance is None:
             inst = cls(*args, **kwargs)
             # Now make sure that the instance will also be returned by
             # parent classes' _instance attribute.
             for subclass in cls._walk_mro():
                 subclass._instance = inst
 
         if isinstance(cls._instance, cls):
             return cls._instance
         else:
             raise MultipleInstanceError(
                 'Multiple incompatible subclass instances of '
                 '%s are being created.' % cls.__name__
             )
 
     @classmethod
     def initialized(cls):
         """Has an instance been created?"""
         return hasattr(cls, "_instance") and cls._instance is not None
 
 
 class LoggingConfigurable(Configurable):
     """A parent class for Configurables that log.
 
     Subclasses have a log trait, and the default behavior
     is to get the logger from the currently running Application
     via Application.instance().log.
     """
 
     log = Instance('logging.Logger')
     def _log_default(self):
         from IPython.config.application import Application
         return Application.instance().log
 
 

IPython/config/tests/test_configurable.py

@@ -1,183 +1,239 b''
 # encoding: utf-8
 """
 Tests for IPython.config.configurable
 
 Authors:
 
 * Brian Granger
 * Fernando Perez (design help)
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 from unittest import TestCase
 
 from IPython.config.configurable import (
     Configurable, 
     SingletonConfigurable
 )
 
 from IPython.utils.traitlets import (
     Integer, Float, Unicode
 )
 
 from IPython.config.loader import Config
 from IPython.utils.py3compat import PY3
 
 #-----------------------------------------------------------------------------
 # Test cases
 #-----------------------------------------------------------------------------
 
 
 class MyConfigurable(Configurable):
     a = Integer(1, config=True, help="The integer a.")
     b = Float(1.0, config=True, help="The integer b.")
     c = Unicode('no config')
 
 
 mc_help=u"""MyConfigurable options
 ----------------------
 --MyConfigurable.a=<Integer>
     Default: 1
     The integer a.
 --MyConfigurable.b=<Float>
     Default: 1.0
     The integer b."""
 
 mc_help_inst=u"""MyConfigurable options
 ----------------------
 --MyConfigurable.a=<Integer>
     Current: 5
     The integer a.
 --MyConfigurable.b=<Float>
     Current: 4.0
     The integer b."""
 
 # On Python 3, the Integer trait is a synonym for Int
 if PY3:
     mc_help = mc_help.replace(u"<Integer>", u"<Int>")
     mc_help_inst = mc_help_inst.replace(u"<Integer>", u"<Int>")
 
 class Foo(Configurable):
     a = Integer(0, config=True, help="The integer a.")
     b = Unicode('nope', config=True)
 
 
 class Bar(Foo):
     b = Unicode('gotit', config=False, help="The string b.")
     c = Float(config=True, help="The string c.")
 
 
 class TestConfigurable(TestCase):
 
     def test_default(self):
         c1 = Configurable()
         c2 = Configurable(config=c1.config)
         c3 = Configurable(config=c2.config)
         self.assertEqual(c1.config, c2.config)
         self.assertEqual(c2.config, c3.config)
 
     def test_custom(self):
         config = Config()
         config.foo = 'foo'
         config.bar = 'bar'
         c1 = Configurable(config=config)
         c2 = Configurable(config=c1.config)
         c3 = Configurable(config=c2.config)
         self.assertEqual(c1.config, config)
         self.assertEqual(c2.config, config)
         self.assertEqual(c3.config, config)
         # Test that copies are not made
         self.assertTrue(c1.config is config)
         self.assertTrue(c2.config is config)
         self.assertTrue(c3.config is config)
         self.assertTrue(c1.config is c2.config)
         self.assertTrue(c2.config is c3.config)
         
     def test_inheritance(self):
         config = Config()
         config.MyConfigurable.a = 2
         config.MyConfigurable.b = 2.0
         c1 = MyConfigurable(config=config)
         c2 = MyConfigurable(config=c1.config)
         self.assertEqual(c1.a, config.MyConfigurable.a)
         self.assertEqual(c1.b, config.MyConfigurable.b)
         self.assertEqual(c2.a, config.MyConfigurable.a)
         self.assertEqual(c2.b, config.MyConfigurable.b)
 
     def test_parent(self):
         config = Config()
         config.Foo.a = 10
         config.Foo.b = "wow"
         config.Bar.b = 'later'
         config.Bar.c = 100.0
         f = Foo(config=config)
         b = Bar(config=f.config)
         self.assertEqual(f.a, 10)
         self.assertEqual(f.b, 'wow')
         self.assertEqual(b.b, 'gotit')
         self.assertEqual(b.c, 100.0)
 
     def test_override1(self):
         config = Config()
         config.MyConfigurable.a = 2
         config.MyConfigurable.b = 2.0
         c = MyConfigurable(a=3, config=config)
         self.assertEqual(c.a, 3)
         self.assertEqual(c.b, config.MyConfigurable.b)
         self.assertEqual(c.c, 'no config')
 
     def test_override2(self):
         config = Config()
         config.Foo.a = 1
         config.Bar.b = 'or'  # Up above b is config=False, so this won't do it.
         config.Bar.c = 10.0
         c = Bar(config=config)
         self.assertEqual(c.a, config.Foo.a)
         self.assertEqual(c.b, 'gotit')
         self.assertEqual(c.c, config.Bar.c)
         c = Bar(a=2, b='and', c=20.0, config=config)
         self.assertEqual(c.a, 2)
         self.assertEqual(c.b, 'and')
         self.assertEqual(c.c, 20.0)
 
     def test_help(self):
         self.assertEqual(MyConfigurable.class_get_help(), mc_help)
 
     def test_help_inst(self):
         inst = MyConfigurable(a=5, b=4)
         self.assertEqual(MyConfigurable.class_get_help(inst), mc_help_inst)
 
 
 class TestSingletonConfigurable(TestCase):
 
     def test_instance(self):
         from IPython.config.configurable import SingletonConfigurable
         class Foo(SingletonConfigurable): pass
         self.assertEqual(Foo.initialized(), False)
         foo = Foo.instance()
         self.assertEqual(Foo.initialized(), True)
         self.assertEqual(foo, Foo.instance())
         self.assertEqual(SingletonConfigurable._instance, None)
 
     def test_inheritance(self):
         class Bar(SingletonConfigurable): pass
         class Bam(Bar): pass
         self.assertEqual(Bar.initialized(), False)
         self.assertEqual(Bam.initialized(), False)
         bam = Bam.instance()
         bam == Bar.instance()
         self.assertEqual(Bar.initialized(), True)
         self.assertEqual(Bam.initialized(), True)
         self.assertEqual(bam, Bam._instance)
         self.assertEqual(bam, Bar._instance)
         self.assertEqual(SingletonConfigurable._instance, None)
+
+
+class MyParent(Configurable):
+    pass
+
+class MyParent2(MyParent):
+    pass
+
+class TestParentConfigurable(TestCase):
+    
+    def test_parent_config(self):
+        
+        cfg = Config({
+            'MyParent' : {
+                'MyConfigurable' : {
+                    'b' : 2.0,
+                }
+            }
+        })
+        parent = MyParent(config=cfg)
+        myc = MyConfigurable(parent=parent)
+        self.assertEqual(myc.b, parent.config.MyParent.MyConfigurable.b)
+
+    def test_parent_inheritance(self):
+        
+        cfg = Config({
+            'MyParent' : {
+                'MyConfigurable' : {
+                    'b' : 2.0,
+                }
+            }
+        })
+        parent = MyParent2(config=cfg)
+        myc = MyConfigurable(parent=parent)
+        self.assertEqual(myc.b, parent.config.MyParent.MyConfigurable.b)
+
+    def test_parent_priority(self):
+        
+        cfg = Config({
+            'MyConfigurable' : {
+                'b' : 2.0,
+            },
+            'MyParent' : {
+                'MyConfigurable' : {
+                    'b' : 3.0,
+                }
+            },
+            'MyParent2' : {
+                'MyConfigurable' : {
+                    'b' : 4.0,
+                }
+            }
+        })
+        parent = MyParent2(config=cfg)
+        myc = MyConfigurable(parent=parent)
+        self.assertEqual(myc.b, parent.config.MyParent2.MyConfigurable.b)