Fixed #4136 -- Made ModelForm save empty values for nullable CharFields as NULL.

Previously, empty values were saved as strings.

4 files changed, 24 insertions, 6 deletions

diff --git a/docs/ref/forms/fields.txt b/docs/ref/forms/fields.txt
index 7144a46a9d..0a5703c46e 100644
--- a/docs/ref/forms/fields.txt
+++ b/docs/ref/forms/fields.txt
@@ -361,7 +361,7 @@ For each field, we describe the default widget used if you don't specify
 .. class:: CharField(**kwargs)
 
     * Default widget: :class:`TextInput`
-    * Empty value: ``''`` (an empty string)
+    * Empty value: Whatever you've given as :attr:`empty_value`.
     * Normalizes to: A Unicode object.
     * Validates ``max_length`` or ``min_length``, if they are provided.
       Otherwise, all inputs are valid.
@@ -380,6 +380,12 @@ For each field, we describe the default widget used if you don't specify
        If ``True`` (default), the value will be stripped of leading and
        trailing whitespace.
 
+    .. attribute:: empty_value
+
+       .. versionadded:: 1.11
+
+       The value to use to represent "empty". Defaults to an empty string.
+
 ``ChoiceField``
 ---------------
 
diff --git a/docs/ref/models/fields.txt b/docs/ref/models/fields.txt
index a56c445c31..2435201db8 100644
--- a/docs/ref/models/fields.txt
+++ b/docs/ref/models/fields.txt
@@ -43,11 +43,13 @@ If ``True``, Django will store empty values as ``NULL`` in the database. Default
 is ``False``.
 
 Avoid using :attr:`~Field.null` on string-based fields such as
-:class:`CharField` and :class:`TextField` because empty string values will
-always be stored as empty strings, not as ``NULL``. If a string-based field has
+:class:`CharField` and :class:`TextField`. If a string-based field has
 ``null=True``, that means it has two possible values for "no data": ``NULL``,
 and the empty string. In most cases, it's redundant to have two possible values
-for "no data;" the Django convention is to use the empty string, not ``NULL``.
+for "no data;" the Django convention is to use the empty string, not
+``NULL``. One exception is when a :class:`CharField` has both ``unique=True``
+and ``blank=True`` set. In this situation, ``null=True`` is required to avoid
+unique constraint violations when saving multiple objects with blank values.
 
 For both string-based and non-string-based fields, you will also need to
 set ``blank=True`` if you wish to permit empty values in forms, as the
diff --git a/docs/releases/1.11.txt b/docs/releases/1.11.txt
index d2e3e74fdd..709c4052f1 100644
--- a/docs/releases/1.11.txt
+++ b/docs/releases/1.11.txt
@@ -154,7 +154,8 @@ File Uploads
 Forms
 ~~~~~
 
-* ...
+* The new :attr:`CharField.empty_value <django.forms.CharField.empty_value>`
+  attribute allows specifying the Python value to use to represent "empty".
 
 Generic Views
 ~~~~~~~~~~~~~
@@ -258,6 +259,13 @@ Miscellaneous
   displays the related object's ID. Remove the ``_id`` suffix if you want the
   old behavior of the string representation of the object.
 
+* In model forms, :class:`~django.db.models.CharField` with ``null=True`` now
+  saves ``NULL`` for blank values instead of empty strings.
+
+* On Oracle, :meth:`Model.validate_unique()
+  <django.db.models.Model.validate_unique>` no longer checks empty strings for
+  uniqueness as the database interprets the value as ``NULL``.
+
 .. _deprecated-features-1.11:
 
 Features deprecated in 1.11
diff --git a/docs/topics/forms/modelforms.txt b/docs/topics/forms/modelforms.txt
index 938516050a..9dcb2e3e53 100644
--- a/docs/topics/forms/modelforms.txt
+++ b/docs/topics/forms/modelforms.txt
@@ -66,7 +66,9 @@ Model field                         Form field
 
 :class:`CharField`                  :class:`~django.forms.CharField` with
                                     ``max_length`` set to the model field's
-                                    ``max_length``
+                                    ``max_length`` and
+                                    :attr:`~django.forms.CharField.empty_value`
+                                    set to ``None`` if ``null=True``.
 
 :class:`CommaSeparatedIntegerField` :class:`~django.forms.CharField`