Fixed #32347 -- Made ModelChoiceField include the value in ValidationError for invalid_choice.

AUTHORS

@@ -442,6 +442,7 @@ answer newbie questions, and generally made Django that much better:
     Jeremy Carbaugh <jcarbaugh@gmail.com>
     Jeremy Dunck <jdunck@gmail.com>
     Jeremy Lainé <jeremy.laine@m4x.org>
+    Jerin Peter George <jerinpetergeorge@gmail.com>
     Jesse Young <adunar@gmail.com>
     Jezeniel Zapanta <jezeniel.zapanta@gmail.com>
     jhenry <jhenry@theonion.com>

django/forms/models.py

@@ -1284,7 +1284,11 @@ class ModelChoiceField(ChoiceField):
                 value = getattr(value, key)
             value = self.queryset.get(**{key: value})
         except (ValueError, TypeError, self.queryset.model.DoesNotExist):
-            raise ValidationError(self.error_messages['invalid_choice'], code='invalid_choice')
+            raise ValidationError(
+                self.error_messages['invalid_choice'],
+                code='invalid_choice',
+                params={'value': value},
+            )
         return value
 
     def validate(self, value):

docs/ref/forms/fields.txt

@@ -1219,6 +1219,9 @@ generating choices. See :ref:`iterating-relationship-choices` for details.
     * Validates that the given id exists in the queryset.
     * Error message keys: ``required``, ``invalid_choice``
 
+    The ``invalid_choice`` error message may contain ``%(value)s``, which will
+    be replaced with the selected choice.
+
     Allows the selection of a single model object, suitable for representing a
     foreign key. Note that the default widget for ``ModelChoiceField`` becomes
     impractical when the number of entries increases. You should avoid using it
@@ -1307,6 +1310,11 @@ generating choices. See :ref:`iterating-relationship-choices` for details.
             def label_from_instance(self, obj):
                 return "My Object #%i" % obj.id
 
+    .. versionchanged:: 4.0
+
+        Support for containing ``%(value)s`` in the ``invalid_choice`` error
+        message was added.
+
 ``ModelMultipleChoiceField``
 ----------------------------
 

docs/releases/4.0.txt

@@ -135,7 +135,11 @@ File Uploads
 Forms
 ~~~~~
 
-* ...
+* :class:`~django.forms.ModelChoiceField` now includes the provided value in
+  the ``params`` argument of a raised
+  :exc:`~django.core.exceptions.ValidationError` for the ``invalid_choice``
+  error message. This allows custom error messages to use the ``%(value)s``
+  placeholder.
 
 Generic Views
 ~~~~~~~~~~~~~

tests/forms_tests/tests/test_error_messages.py

@@ -308,3 +308,16 @@ class ModelChoiceFieldErrorMessagesTestCase(TestCase, AssertFormErrorsMixin):
         self.assertFormErrors(['REQUIRED'], f.clean, '')
         self.assertFormErrors(['NOT A LIST OF VALUES'], f.clean, '3')
         self.assertFormErrors(['4 IS INVALID CHOICE'], f.clean, ['4'])
+
+    def test_modelchoicefield_value_placeholder(self):
+        f = ModelChoiceField(
+            queryset=ChoiceModel.objects.all(),
+            error_messages={
+                'invalid_choice': '"%(value)s" is not one of the available choices.',
+            },
+        )
+        self.assertFormErrors(
+            ['"invalid" is not one of the available choices.'],
+            f.clean,
+            'invalid',
+        )