Merge pull request #10 from cjw296/prepare

The "prepare" stuff myself and mcdonc discussed.

CHANGES.txt

@@ -14,6 +14,9 @@ Next release
   ``colander.DateTime``.  See
   https://github.com/Pylons/colander/issues#issue/6.
 
+- Add the ability to insert a :class:`~colander.interfaces.Preparer`
+  between deserialization and validation. See the :ref:`preparing`.
+
 0.9.2 (2011-03-28)
 ------------------
 

CONTRIBUTORS.txt

@@ -102,4 +102,4 @@ Contributors
 ------------
 
 - Chris McDonough, 2011/02/16
-
+- Chris Withers, 2011/05/45

colander/__init__.py

@@ -1231,6 +1231,10 @@ class SchemaNode(object):
       'required'.  When ``missing`` is :attr:`colander.required`, the
       ``required`` computed attribute will be ``True``.
 
+    - ``preparer``: Optional preparer for this node.  It should be
+      an object that implements the
+      :class:`colander.interfaces.Preparer` interface.
+
     - ``validator``: Optional validator for this node.  It should be
       an object that implements the
       :class:`colander.interfaces.Validator` interface.
@@ -1275,6 +1279,7 @@ class SchemaNode(object):
         
     def __init__(self, typ, *children, **kw):
         self.typ = typ
+        self.preparer = kw.pop('preparer', None)
         self.validator = kw.pop('validator', None)
         self.default = kw.pop('default', null)
         self.missing = kw.pop('missing', required)
@@ -1338,13 +1343,14 @@ class SchemaNode(object):
 
     def deserialize(self, cstruct=null):
         """ Deserialize the :term:`cstruct` into an :term:`appstruct` based
-        on the schema, and return the deserialized, then validate the
-        resulting appstruct.  The ``cstruct`` value is deserialized into an
+        on the schema, run this :term:`appstruct` through the
+        preparer, if one is present, then validate the
+        prepared appstruct.  The ``cstruct`` value is deserialized into an
         ``appstruct`` unconditionally.
 
-        If ``appstruct`` returned by type deserialization is the value
-        :attr:`colander.null`, do something special before attempting
-        validation:
+        If ``appstruct`` returned by type deserialization and
+        preparation is the value :attr:`colander.null`, do something
+        special before attempting validation:
 
         - If the ``missing`` attribute of this node has been set explicitly,
           return its value.  No validation of this value is performed; it is
@@ -1361,6 +1367,9 @@ class SchemaNode(object):
         """
         appstruct = self.typ.deserialize(self, cstruct)
 
+        if self.preparer is not None:
+            appstruct = self.preparer(appstruct)
+            
         if appstruct is null:
             appstruct = self.missing
             if appstruct is required:

colander/interfaces.py

@@ -1,6 +1,19 @@
+def Preparer(value):
+    """
+    A preparer is called after deserialization of a value but before
+    that value is validated.
+    
+    Any modifications to ``value`` required should be made by
+    returning the modified value rather than modifying in-place.
+
+    If no modification is required, then ``value`` should be returned
+    as-is.
+    """
+
+    
 def Validator(node, value):
     """
-    A validator is called after deserialization of a value.
+    A validator is called after preparation of the deserialized value.
     
     If ``value`` is not valid, raise a :class:`colander.Invalid`
     instance as an exception after.

colander/tests.py

@@ -1463,6 +1463,14 @@ class TestSchemaNode(unittest.TestCase):
         node = self._makeOne(None, 0, widget='abc')
         self.assertEqual(node.widget, 'abc')
 
+    def test_ctor_with_preparer(self):
+        node = self._makeOne(None, 0, preparer='abc')
+        self.assertEqual(node.preparer, 'abc')
+
+    def test_ctor_without_preparer(self):
+        node = self._makeOne(None, 0)
+        self.assertEqual(node.preparer, None)
+
     def test_ctor_with_unknown_kwarg(self):
         node = self._makeOne(None, 0, foo=1)
         self.assertEqual(node.foo, 1)
@@ -1486,6 +1494,29 @@ class TestSchemaNode(unittest.TestCase):
         result = node.deserialize(1)
         self.assertEqual(result, 1)
 
+    def test_deserialize_with_preparer(self):
+        from colander import Invalid
+        typ = DummyType()
+        def preparer(value):
+            return 'prepared_'+value
+        def validator(node, value):
+            if not value.startswith('prepared'):
+                raise Invalid(node, 'not prepared')
+        node = self._makeOne(typ,
+                             preparer=preparer,
+                             validator=validator)
+        self.assertEqual(node.deserialize('value'),
+                         'prepared_value')
+
+    def test_deserialize_preparer_before_missing_check(self):
+        from colander import null
+        typ = DummyType()
+        def preparer(value):
+            return null
+        node = self._makeOne(typ,preparer=preparer)
+        e = invalid_exc(node.deserialize, 1)
+        self.assertEqual(e.msg, 'Required')
+
     def test_deserialize_with_validator(self):
         typ = DummyType()
         validator = DummyValidator(msg='Wrong')

docs/basics.rst

@@ -89,20 +89,29 @@ Schema Node Objects
 
 A schema is composed of one or more *schema node* objects, each typically of
 the class :class:`colander.SchemaNode`, usually in a nested arrangement.
-Each schema node object has a required *type*, an optional deserialization
-*validator*, an optional *default*, an optional *missing*, an optional
-*title*, an optional *description*, and a slightly less optional *name*.  It
-also accepts *arbitrary* keyword arguments, which are attached directly as
-attributes to the node instance.
+Each schema node object has a required *type*, an optional *preparer*
+for adjusting data after deserialization, an optional
+*validator* for deserialized prepared data, an optional *default*, an
+optional *missing*, an optional *title*, an optional *description*,
+and a slightly less optional *name*.  It also accepts *arbitrary*
+keyword arguments, which are attached directly as attributes to the
+node instance.
 
 The *type* of a schema node indicates its data type (such as
 :class:`colander.Int` or :class:`colander.String`).
 
-The *validator* of a schema node is called after deserialization; it
-makes sure the deserialized value matches a constraint.  An example of
+The *preparer* of a schema node is called after
+deserialization but before validation; it prepares a deserialized
+value for validation. Examples would be to prepend schemes that may be
+missing on url values or to filter html provided by a rich text
+editor. A preparer is not called during serialization, only during
+deserialization.
+
+The *validator* of a schema node is called after deserialization and
+preparation ; it makes sure the value matches a constraint.  An example of
 such a validator is provided in the schema above:
 ``validator=colander.Range(0, 200)``.  A validator is not called after
-serialization, only after deserialization.
+schema node serialization, only after node deserialization.
 
 The *default* of a schema node indicates the value to be serialized if
 a value for the schema node is not found in the input data during
@@ -392,6 +401,40 @@ which the exception is related.
 See the :class:`colander.Invalid` API documentation for more
 information.
 
+.. _preparing:
+
+Preparing deserialized data for validation
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In certain circumstances, it is necessary to modify the deserialized
+value before validating it.
+
+For example, a :class:`~colander.String` node may be required to
+contain content, but that content may come from a rich text
+editor. Such an editor may return ``<b></b>`` which may appear to be
+valid but doesn't contain content, or 
+``<a href="javascript:alert('evil'')">good</a>`` which is valid, but
+only after some processing.
+
+The following schema uses `htmllaundry`__ and a
+:class:`~colander.interfaces.Preparer` to do the correct thing in both
+cases:
+
+__ http://pypi.python.org/pypi/htmllaundry/
+
+.. code-block:: python
+   :linenos:
+
+   import colander
+   import htmlaundry
+
+   class Page(colander.MappingSchema):
+       title = colander.SchemaNode(colander.String())
+       content = colander.SchemaNode(colander.String(),
+                                     preparer=htmllaundry.sanitize,
+                                     validator=colander.Length(1))
+
+
 Serialization
 -------------
 

docs/interfaces.rst

@@ -3,6 +3,8 @@ Interfaces
 
 .. automodule:: colander.interfaces
 
+  .. autofunction:: Preparer
+
   .. autofunction:: Validator
 
   .. autoclass:: Type