Fixed django#5986 -- Added ability to customize order of Form fields

Author: ttanner

django/contrib/auth/forms.py

@@ -1,7 +1,5 @@
 from __future__ import unicode_literals
 
-from collections import OrderedDict
-
 from django import forms
 from django.contrib.auth import authenticate, get_user_model
 from django.contrib.auth.hashers import (
@@ -303,6 +301,8 @@ class PasswordChangeForm(SetPasswordForm):
     old_password = forms.CharField(label=_("Old password"),
                                    widget=forms.PasswordInput)
 
+    field_order = ['old_password', 'new_password1', 'new_password2']
+
     def clean_old_password(self):
         """
         Validates that the old_password field is correct.
@@ -315,11 +315,6 @@ def clean_old_password(self):
             )
         return old_password
 
-PasswordChangeForm.base_fields = OrderedDict(
-    (k, PasswordChangeForm.base_fields[k])
-    for k in ['old_password', 'new_password1', 'new_password2']
-)
-
 
 class AdminPasswordChangeForm(forms.Form):
     """

django/forms/forms.py

@@ -73,9 +73,11 @@ class BaseForm(object):
     # class is different than Form. See the comments by the Form class for more
     # information. Any improvements to the form API should be made to *this*
     # class, not to the Form class.
+    field_order = None
+
     def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
                  initial=None, error_class=ErrorList, label_suffix=None,
-                 empty_permitted=False):
+                 empty_permitted=False, field_order=None):
         self.is_bound = data is not None or files is not None
         self.data = data or {}
         self.files = files or {}
@@ -96,6 +98,29 @@ def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
         # self.base_fields.
         self.fields = copy.deepcopy(self.base_fields)
         self._bound_fields_cache = {}
+        self.order_fields(self.field_order if field_order is None else field_order)
+
+    def order_fields(self, field_order):
+        """
+        Rearranges the fields according to field_order.
+
+        field_order is a list of field names specifying the order. Fields not
+        included in the list are appended in the default order for backward
+        compatibility with subclasses not overriding field_order. If field_order
+        is None, all fields are kept in the order defined in the class.
+        Unknown fields in field_order are ignored to allow disabling fields in
+        form subclasses without redefining ordering.
+        """
+        if field_order is None:
+            return
+        fields = OrderedDict()
+        for key in field_order:
+            try:
+                fields[key] = self.fields.pop(key)
+            except KeyError:  # ignore unknown fields
+                pass
+        fields.update(self.fields)  # add remaining fields in original order
+        self.fields = fields
 
     def __str__(self):
         return self.as_table()

docs/ref/forms/api.txt

@@ -700,6 +700,31 @@ example, in the ``ContactForm`` example, the fields are defined in the order
 ``subject``, ``message``, ``sender``, ``cc_myself``. To reorder the HTML
 output, just change the order in which those fields are listed in the class.
 
+There are several other ways to customize the order:
+
+.. attribute:: Form.field_order
+
+.. versionadded:: 1.9
+
+By default ``Form.field_order=None``, which retains the order in which you
+define the fields in your form class. If ``field_order`` is a list of field
+names, the fields are ordered as specified by the list and remaining fields are
+appended according to the default order. Unknown field names in the list are
+ignored. This makes it possible to disable a field in a subclass by setting it
+to ``None`` without having to redefine ordering.
+
+You can also use the ``Form.field_order`` argument to a :class:`Form` to
+override the field order. If a :class:`~django.forms.Form` defines
+:attr:`~Form.field_order` *and* you include ``field_order`` when instantiating
+the ``Form``, then the latter ``field_order`` will have precedence.
+
+.. method:: Form.order_fields(field_order)
+
+.. versionadded:: 1.9
+
+You may rearrange the fields any time using ``order_fields()`` with a list of
+field names as in :attr:`~django.forms.Form.field_order`.
+
 How errors are displayed
 ~~~~~~~~~~~~~~~~~~~~~~~~
 

docs/releases/1.9.txt

@@ -119,6 +119,10 @@ Forms
   ``field_classes`` to customize the type of the fields. See
   :ref:`modelforms-overriding-default-fields` for details.
 
+* You can now specify the order in which form fields are rendered with the
+  :attr:`~django.forms.Form.field_order` attribute, the ``field_order``
+  constructor argument , or the :meth:`~django.forms.Form.order_fields` method.
+
 Generic Views
 ^^^^^^^^^^^^^
 

tests/forms_tests/tests/test_forms.py

@@ -1046,6 +1046,49 @@ class TestForm(Form):
 <tr><th>Field13:</th><td><input type="text" name="field13" /></td></tr>
 <tr><th>Field14:</th><td><input type="text" name="field14" /></td></tr>""")
 
+    def test_explicit_field_order(self):
+        class TestFormParent(Form):
+            field1 = CharField()
+            field2 = CharField()
+            field4 = CharField()
+            field5 = CharField()
+            field6 = CharField()
+            field_order = ['field6', 'field5', 'field4', 'field2', 'field1']
+
+        class TestForm(TestFormParent):
+            field3 = CharField()
+            field_order = ['field2', 'field4', 'field3', 'field5', 'field6']
+
+        class TestFormRemove(TestForm):
+            field1 = None
+
+        class TestFormMissing(TestForm):
+            field_order = ['field2', 'field4', 'field3', 'field5', 'field6', 'field1']
+            field1 = None
+
+        class TestFormInit(TestFormParent):
+            field3 = CharField()
+            field_order = None
+
+            def __init__(self, **kwargs):
+                super(TestFormInit, self).__init__(**kwargs)
+                self.order_fields(field_order=TestForm.field_order)
+
+        p = TestFormParent()
+        self.assertEqual(list(p.fields.keys()), TestFormParent.field_order)
+        p = TestFormRemove()
+        self.assertEqual(list(p.fields.keys()), TestForm.field_order)
+        p = TestFormMissing()
+        self.assertEqual(list(p.fields.keys()), TestForm.field_order)
+        p = TestForm()
+        self.assertEqual(list(p.fields.keys()), TestFormMissing.field_order)
+        p = TestFormInit()
+        order = list(TestForm.field_order) + ['field1']
+        self.assertEqual(list(p.fields.keys()), order)
+        TestForm.field_order = ['unknown']
+        p = TestForm()
+        self.assertEqual(list(p.fields.keys()), ['field1', 'field2', 'field4', 'field5', 'field6', 'field3'])
+
     def test_form_html_attributes(self):
         # Some Field classes have an effect on the HTML attributes of their associated
         # Widget. If you set max_length in a CharField and its associated widget is