Added support for Type and Instance traitlets with testing.

IPython/utils/tests/test_traitlets.py

@@ -30,7 +30,8 b' from unittest import TestCase'
 
 from IPython.utils.traitlets import (
     HasTraitlets, MetaHasTraitlets, TraitletType, Any,
-    Int, Long, Float, Complex, Str, Unicode, Bool, TraitletError
+    Int, Long, Float, Complex, Str, Unicode, Bool, TraitletError,
+    Undefined, Type, Instance
 )
 
 
@@ -65,15 +66,15 b' class TestTraitletType(TestCase):'
         self.tt.name = self.name
         self.hast = HasTraitletsStub() 
 
-    def test_get(self):
+    def test_get_undefined(self):
         value = self.tt.__get__(self.hast)
-        self.assertEquals(value, None)
+        self.assertEquals(value, Undefined)
 
     def test_set(self):
         self.tt.__set__(self.hast, 10)
         self.assertEquals(self.hast._traitlet_values[self.name],10)
         self.assertEquals(self.hast._notify_name,self.name)
-        self.assertEquals(self.hast._notify_old,None)
+        self.assertEquals(self.hast._notify_old,Undefined)
         self.assertEquals(self.hast._notify_new,10)
 
     def test_validate(self):
@@ -85,6 +86,20 b' class TestTraitletType(TestCase):'
         tt.__set__(self.hast, 10)
         self.assertEquals(tt.__get__(self.hast),-1)
 
+    def test_default_validate(self):
+        class MyIntTT(TraitletType):
+            def validate(self, obj, value):
+                if isinstance(value, int):
+                    return value
+                self.error(obj, value)
+        tt = MyIntTT(10)
+        tt.name = 'a'
+        self.assertEquals(tt.__get__(self.hast), 10)
+        tt = MyIntTT('bad default')
+        tt.name = 'b' # different name from 'a' as we want an unset dv
+        self.assertRaises(TraitletError, tt.__get__, self.hast)
+            
+
     def test_is_valid_for(self):
         class MyTT(TraitletType):
             def is_valid_for(self, value):
@@ -311,7 +326,113 b' class TestAddTraitlet(TestCase):'
 # Tests for specific traitlet types
 #-----------------------------------------------------------------------------
 
+
+class TestType(TestCase):
+
+    def test_default(self):
+
+        class B(object): pass
+        class A(HasTraitlets):
+            klass = Type
+
+        a = A()
+        self.assertEquals(a.klass, None)
+        a.klass = B
+        self.assertEquals(a.klass, B)
+        self.assertRaises(TraitletError, setattr, a, 'klass', 10)
+
+    def test_value(self):
+
+        class B(object): pass
+        class C(object): pass
+        class A(HasTraitlets):
+            klass = Type(B)
+        
+        a = A()
+        self.assertEquals(a.klass, B)
+        self.assertRaises(TraitletError, setattr, a, 'klass', C)
+        self.assertRaises(TraitletError, setattr, a, 'klass', object)
+        a.klass = B
+
+    def test_allow_none(self):
+
+        class B(object): pass
+        class C(B): pass
+        class A(HasTraitlets):
+            klass = Type(B, allow_none=False)
+
+        a = A()
+        self.assertEquals(a.klass, B)
+        self.assertRaises(TraitletError, setattr, a, 'klass', None)
+        a.klass = C
+        self.assertEquals(a.klass, C)
+
+
+class TestInstance(TestCase):
+
+    def test_basic(self):
+        class Foo(object): pass
+        class Bar(Foo): pass
+        class Bah(object): pass
+        
+        class A(HasTraitlets):
+            inst = Instance(Foo)
+
+        a = A()
+        self.assert_(isinstance(a.inst, Foo))
+        a.inst = Foo()
+        self.assert_(isinstance(a.inst, Foo))
+        a.inst = Bar()
+        self.assert_(isinstance(a.inst, Foo))
+        self.assertRaises(TraitletError, setattr, a, 'inst', Foo)
+        self.assertRaises(TraitletError, setattr, a, 'inst', Bar)
+        self.assertRaises(TraitletError, setattr, a, 'inst', Bah())
+
+    def test_unique_default_value(self):
+        class Foo(object): pass        
+        class A(HasTraitlets):
+            inst = Instance(Foo)
+
+        a = A()
+        b = A()
+        self.assert_(a.inst is not b.inst)
+
+    def test_args_kw(self):
+        class Foo(object):
+            def __init__(self, c): self.c = c
+
+        class A(HasTraitlets):
+            inst = Instance(Foo, args=(10,))
+
+        a = A()
+        self.assertEquals(a.inst.c, 10)
+
+        class Bar(object):
+            def __init__(self, c, d):
+                self.c = c; self.d = d
+
+        class B(HasTraitlets):
+            inst = Instance(Bar, args=(10,),kw=dict(d=20))
+        b = B()
+        self.assertEquals(b.inst.c, 10)
+        self.assertEquals(b.inst.d, 20)
+
+    def test_instance(self):
+        # Does passing an instance yield a default value of None?
+        class Foo(object): pass
+
+        class A(HasTraitlets):
+            inst = Instance(Foo())
+        a = A()
+        self.assertEquals(a.inst, None)
+        
+        class B(HasTraitlets):
+            inst = Instance(Foo(), allow_none=False)
+        b = B()
+        self.assertRaises(TraitletError, getattr, b, 'inst')
+
 class TraitletTestBase(TestCase):
+    """A best testing class for basic traitlet types."""
 
     def assign(self, value):
         self.obj.value = value

IPython/utils/traitlets.py

@@ -42,9 +42,13 b' Authors:'
 # Imports
 #-----------------------------------------------------------------------------
 
+
 import inspect
+import sys
 import types
-from types import InstanceType
+from types import InstanceType, ClassType
+
+ClassTypes = (ClassType, type)
 
 #-----------------------------------------------------------------------------
 # Basic classes
@@ -124,6 +128,12 b' def parse_notifier_name(name):'
         return name
 
 
+def get_module_name ( level = 2 ):
+    """ Returns the name of the module that the caller's caller is located in.
+    """
+    return sys._getframe( level ).f_globals.get( '__name__', '__main__' )
+
+
 #-----------------------------------------------------------------------------
 # Base TraitletType for all traitlets
 #-----------------------------------------------------------------------------
@@ -132,30 +142,55 b' def parse_notifier_name(name):'
 class TraitletType(object):
 
     metadata = {}
-    default_value = None
+    default_value = Undefined
     info_text = 'any value'
 
     def __init__(self, default_value=NoDefaultSpecified, **metadata):
+        """Create a TraitletType.
+        """
         if default_value is not NoDefaultSpecified:
             self.default_value = default_value
         self.metadata.update(metadata)
+        self.init()
 
-    def __get__(self, inst, cls=None):
-        if inst is None:
+    def init(self):
+        pass
+
+    def get_default_value(self):
+        """Create a new instance of the default value."""
+        dv = self.default_value
+        return dv
+
+    def __get__(self, obj, cls=None):
+        """Get the value of the traitlet by self.name for the instance.
+        
+        The creation of default values is deferred until this is called the
+        first time.  This is done so instances of the parent HasTraitlets
+        will have their own default value instances.
+        """
+        if obj is None:
             return self
         else:
-            return inst._traitlet_values.get(self.name, self.default_value)
+            if not obj._traitlet_values.has_key(self.name):
+                dv = self.get_default_value()
+                self.__set__(obj, dv, first=True)
+                return dv
+            else:
+                return obj._traitlet_values[self.name]
 
-    def __set__(self, inst, value):
-        new_value = self._validate(inst, value)
-        old_value = self.__get__(inst)
+    def __set__(self, obj, value, first=False):
+        new_value = self._validate(obj, value)
+        if not first:
+            old_value = self.__get__(obj)
         if old_value != new_value:
-            inst._traitlet_values[self.name] = new_value
-            inst._notify(self.name, old_value, new_value)
+                obj._traitlet_values[self.name] = new_value
+                obj._notify(self.name, old_value, new_value)
+        else:
+            obj._traitlet_values[self.name] = new_value
 
-    def _validate(self, inst, value):
+    def _validate(self, obj, value):
         if hasattr(self, 'validate'):
-            return self.validate(inst, value)
+            return self.validate(obj, value)
         elif hasattr(self, 'is_valid_for'):
             valid = self.is_valid_for(value)
             if valid:
@@ -333,10 +368,291 b' class HasTraitlets(object):'
         inst.name = name
         setattr(self.__class__, name, inst)
 
+
 #-----------------------------------------------------------------------------
 # Actual TraitletTypes implementations/subclasses
 #-----------------------------------------------------------------------------
 
+#-----------------------------------------------------------------------------
+# TraitletTypes subclasses for handling classes and instances of classes
+#-----------------------------------------------------------------------------
+
+
+class BaseClassResolver(TraitletType):
+    """Mixin class for traitlets that need to resolve classes by strings.
+    
+    This class provides is a mixin that provides its subclasses with the 
+    ability to resolve classes by specifying a string name (for example,
+    'foo.bar.MyClass').  An actual class can also be resolved.
+
+    Any subclass must define instances with 'klass' and 'module' attributes
+    that contain the string name of the class (or actual class object) and
+    the module name that contained the original trait definition (used for
+    resolving local class names (e.g. 'LocalClass')).
+    """
+
+    def resolve_class(self, obj, value):
+        klass = self.validate_class(self.find_class(self.klass))
+        if klass is None:
+            self.validate_failed(obj, value)
+
+        self.klass = klass
+
+    def validate_class(self, klass):
+        return klass
+
+    def find_class(self, klass):
+        module = self.module
+        col    = klass.rfind('.')
+        if col >= 0:
+            module = klass[ : col ]
+            klass = klass[ col + 1: ]
+
+        theClass = getattr(sys.modules.get(module), klass, None)
+        if (theClass is None) and (col >= 0):
+            try:
+                mod = __import__(module)
+                for component in module.split( '.' )[1:]:
+                    mod = getattr(mod, component)
+
+                theClass = getattr(mod, klass, None)
+            except:
+                pass
+
+        return theClass
+
+    def validate_failed (self, obj, value):
+        kind = type(value)
+        if kind is InstanceType:
+            msg = 'class %s' % value.__class__.__name__
+        else:
+            msg = '%s (i.e. %s)' % ( str( kind )[1:-1], repr( value ) )
+
+        self.error(obj, msg)
+
+
+class Type(BaseClassResolver):
+    """A traitlet whose value must be a subclass of a specified class."""
+
+    def __init__ (self, default_value=None, klass=None, allow_none=True, **metadata ):
+        """Construct a Type traitlet
+
+        A Type traitlet specifies that its values must be subclasses of
+        a particular class.
+
+        Parameters
+        ----------
+        default_value : class or None
+            The default value must be a subclass of klass.
+        klass : class, str, None
+            Values of this traitlet must be a subclass of klass.  The klass
+            may be specified in a string like: 'foo.bar.MyClass'.
+        allow_none : boolean
+            Indicates whether None is allowed as an assignable value. Even if
+            ``False``, the default value may be ``None``.
+        """
+        if default_value is None:
+            if klass is None:
+                klass = object
+        elif klass is None:
+            klass = default_value
+
+        if isinstance(klass, basestring):
+            self.validate = self.resolve
+        elif not isinstance(klass, ClassTypes):
+            raise TraitletError("A Type traitlet must specify a class.")
+
+        self.klass       = klass
+        self._allow_none = allow_none
+        self.module      = get_module_name()
+
+        super(Type, self).__init__(default_value, **metadata)
+
+    def validate(self, obj, value):
+        """Validates that the value is a valid object instance."""
+        try:
+            if issubclass(value, self.klass):
+                return value
+        except:
+            if (value is None) and (self._allow_none):
+                return value
+
+        self.error(obj, value)
+
+    def resolve(self, obj, name, value):
+        """ Resolves a class originally specified as a string into an actual
+            class, then resets the trait so that future calls will be handled by
+            the normal validate method.
+        """
+        if isinstance(self.klass, basestring):
+            self.resolve_class(obj, value)
+            del self.validate
+
+        return self.validate(obj, value)
+
+    def info(self):
+        """ Returns a description of the trait."""
+        klass = self.klass
+        if not isinstance(klass, basestring):
+            klass = klass.__name__
+
+        result = 'a subclass of ' + klass
+
+        if self._allow_none:
+            return result + ' or None'
+
+        return result
+
+    def get_default_value(self):
+        """ Returns a tuple of the form: ( default_value_type, default_value )
+            which describes the default value for this trait.
+        """
+        if not isinstance(self.default_value, basestring):
+            return super(Type, self).get_default_value()
+
+        dv = self.resolve_default_value()
+        dvt = type(dv)
+        return (dvt, dv)
+
+    def resolve_default_value(self):
+        """ Resolves a class name into a class so that it can be used to
+            return the class as the default value of the trait.
+        """
+        if isinstance(self.klass, basestring):
+            try:
+                self.resolve_class(None, None)
+                del self.validate
+            except:
+                raise TraitletError('Could not resolve %s into a valid class' %
+                                    self.klass )
+
+        return self.klass
+
+
+class DefaultValueGenerator(object):
+    """A class for generating new default value instances."""
+
+    def __init__(self, klass, *args, **kw):
+        self.klass = klass
+        self.args = args
+        self.kw = kw
+
+
+class Instance(BaseClassResolver):
+    """A trait whose value must be an instance of a specified class.
+    
+    The value can also be an instance of a subclass of the specified class.
+    """
+
+    def __init__(self, klass=None, args=None, kw=None, allow_none=True, 
+                 module = None, **metadata ):
+        """Construct an Instance traitlet.
+
+        Parameters
+        ----------
+        klass : class or instance
+            The object that forms the basis for the traitlet.  If an instance
+            values must have isinstance(value, type(instance)).
+        args : tuple
+            Positional arguments for generating the default value.
+        kw : dict
+            Keyword arguments for generating the default value.
+        allow_none : bool
+            Indicates whether None is allowed as a value.
+
+        Default Value
+        -------------
+        If klass is an instance, default value is None.  If klass is a class
+        then the default value is obtained by calling ``klass(*args, **kw)``.
+        If klass is a str, it is first resolved to an actual class and then
+        instantiated with ``klass(*args, **kw)``.
+        """
+
+        self._allow_none = allow_none
+        self.module      = module or get_module_name()
+
+        if klass is None:
+            raise TraitletError('A %s traitlet must have a class specified.' %
+                                self.__class__.__name__ )
+        elif not isinstance(klass, (basestring,) + ClassTypes ):
+            # klass is an instance so default value will be None
+            self.klass = klass.__class__
+            default_value = None
+        else:
+            # klass is a str or class so we handle args, kw
+            if args is None:
+                args = ()
+            if kw is None:
+                if isinstance(args, dict):
+                    kw = args
+                    args = ()
+                else:
+                    kw = {}
+            if not isinstance(kw, dict):
+                raise TraitletError("The 'kw' argument must be a dict.")
+            if not isinstance(args, tuple):
+                raise TraitletError("The 'args' argument must be a tuple.")
+            self.klass = klass
+            # This tells my get_default_value that the default value
+            # instance needs to be generated when it is called.  This 
+            # is usually when TraitletType.__get__ is called for the 1st time.
+            
+            default_value = DefaultValueGenerator(klass, *args, **kw)
+
+        super(Instance, self).__init__(default_value, **metadata)
+
+    def validate(self, obj, value):
+        if value is None:
+            if self._allow_none:
+                return value
+            self.validate_failed(obj, value)
+
+        # This is where self.klass is turned into a real class if it was
+        # a str initially.  This happens the first time TraitletType.__set__
+        # is called.  This does happen if a default value is generated by
+        # TraitletType.__get__.
+        if isinstance(self.klass, basestring):
+            self.resolve_class(obj, value)
+
+        if isinstance(value, self.klass):
+            return value
+        else:
+            self.validate_failed(obj, value)
+
+    def info ( self ):
+        klass = self.klass
+        if not isinstance( klass, basestring ):
+            klass = klass.__name__
+        result = class_of(klass)
+        if self._allow_none:
+            return result + ' or None'
+
+        return result
+
+    def get_default_value ( self ):
+        """Instantiate a default value instance.
+        
+        When TraitletType.__get__ is called the first time, this is called
+        (if no value has been assigned) to get a default value instance.
+        """
+        dv  = self.default_value
+        if isinstance(dv, DefaultValueGenerator):
+            klass = dv.klass
+            args = dv.args
+            kw = dv.kw
+            if isinstance(klass, basestring):
+                klass = self.validate_class(self.find_class(klass))
+                if klass is None:
+                    raise TraitletError('Unable to locate class: ' + dv.klass)
+            return klass(*args, **kw)
+        else:
+            return dv
+
+
+#-----------------------------------------------------------------------------
+# Basic TraitletTypes implementations/subclasses
+#-----------------------------------------------------------------------------
+
 
 class Any(TraitletType):
     default_value = None