Added unit tests and docs for the newforms case in which the form's data doesn't include a value for a nonrequired field

git-svn-id: http://code.djangoproject.com/svn/django/trunk@5218 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/newforms.txt

@@ -186,7 +186,7 @@ e-mail address::
     >>> f.is_valid()
     False
 
-Access the ``Form`` attribute ``errors`` to get a dictionary of error messages::
+Access the ``errors`` attribute to get a dictionary of error messages::
 
     >>> f.errors
     {'sender': [u'Enter a valid e-mail address.'], 'subject': [u'This field is required.']}
@@ -199,6 +199,10 @@ You can access ``errors`` without having to call ``is_valid()`` first. The
 form's data will be validated the first time either you call ``is_valid()`` or
 access ``errors``.
 
+The validation routines will only get called once, regardless of how many times
+you access ``errors`` or call ``is_valid()``. This means that if validation has
+side effects, those side effects will only be triggered once.
+
 Behavior of unbound forms
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -276,6 +280,27 @@ but ``clean_data`` contains only the form's fields::
     >>> f.clean_data # Doesn't contain extra_field_1, etc.
     {'cc_myself': True, 'message': u'Hi there', 'sender': u'foo@example.com', 'subject': u'hello'}
 
+``clean_data`` will include a key and value for *all* fields defined in the
+``Form``, even if the data didn't include a value for fields that are not
+required. In this example, the data dictionary doesn't include a value for the
+``nick_name`` field, but ``clean_data`` includes it, with an empty value::
+
+    >>> class OptionalPersonForm(Form):
+    ...     first_name = CharField()
+    ...     last_name = CharField()
+    ...     nick_name = CharField(required=False)
+    >>> data = {'first_name': u'John', 'last_name': u'Lennon'}
+    >>> f = OptionalPersonForm(data)
+    >>> f.is_valid()
+    True
+    >>> f.clean_data
+    {'nick_name': u'', 'first_name': u'John', 'last_name': u'Lennon'}
+
+In this above example, the ``clean_data`` value for ``nick_name`` is set to an
+empty string, because ``nick_name`` is ``CharField``, and ``CharField``s treat
+empty values as an empty string. Each field type knows what its "blank" value
+is -- e.g., for ``DateField``, it's ``None`` instead of the empty string.
+
 Behavior of unbound forms
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 

tests/regressiontests/forms/tests.py

@@ -1916,6 +1916,34 @@ True
 >>> p.clean_data
 {'first_name': u'John', 'last_name': u'Lennon', 'birthday': datetime.date(1940, 10, 9)}
 
+clean_data will include a key and value for *all* fields defined in the Form,
+even if the Form's data didn't include a value for fields that are not
+required. In this example, the data dictionary doesn't include a value for the
+"nick_name" field, but clean_data includes it. For CharFields, it's set to the
+empty string.
+>>> class OptionalPersonForm(Form):
+...     first_name = CharField()
+...     last_name = CharField()
+...     nick_name = CharField(required=False)
+>>> data = {'first_name': u'John', 'last_name': u'Lennon'}
+>>> f = OptionalPersonForm(data)
+>>> f.is_valid()
+True
+>>> f.clean_data
+{'nick_name': u'', 'first_name': u'John', 'last_name': u'Lennon'}
+
+For DateFields, it's set to None.
+>>> class OptionalPersonForm(Form):
+...     first_name = CharField()
+...     last_name = CharField()
+...     birth_date = DateField(required=False)
+>>> data = {'first_name': u'John', 'last_name': u'Lennon'}
+>>> f = OptionalPersonForm(data)
+>>> f.is_valid()
+True
+>>> f.clean_data
+{'birth_date': None, 'first_name': u'John', 'last_name': u'Lennon'}
+
 "auto_id" tells the Form to add an "id" attribute to each form element.
 If it's a string that contains '%s', Django will use that as a format string
 into which the field's name will be inserted. It will also put a <label> around