Fixed #22318 -- Added Form.has_error() to easily check if a given error has happened.

django/forms/forms.py

@@ -334,6 +334,15 @@ class BaseForm(object):
             if field in self.cleaned_data:
                 del self.cleaned_data[field]
 
+    def has_error(self, field, code=None):
+        if code is None:
+            return field in self.errors
+        if field in self.errors:
+            for error in self.errors.as_data()[field]:
+                if error.code == code:
+                    return True
+        return False
+
     def full_clean(self):
         """
         Cleans all of self.data and populates self._errors and

docs/ref/forms/api.txt

@@ -182,6 +182,17 @@ when defining form errors.
 Note that ``Form.add_error()`` automatically removes the relevant field from
 ``cleaned_data``.
 
+.. method:: Form.has_error(field, code=None)
+
+.. versionadded:: 1.8
+
+This method returns a boolean designating whether a field has an error with
+a specific error ``code``. If ``code`` is ``None``, it will return ``True``
+if the field contains any errors at all.
+
+To check for non-field errors use
+:data:`~django.core.exceptions.NON_FIELD_ERRORS` as the ``field`` parameter.
+
 Behavior of unbound forms
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 

docs/releases/1.8.txt

@@ -109,6 +109,9 @@ Forms
 * Form widgets now render attributes with a value of ``True`` or ``False``
   as HTML5 boolean attributes.
 
+* The new :meth:`~django.forms.Form.has_error()` method allows checking
+  if a specific error has happened.
+
 Internationalization
 ^^^^^^^^^^^^^^^^^^^^
 

tests/forms_tests/tests/test_forms.py

@@ -6,6 +6,7 @@ import datetime
 import json
 import warnings
 
+from django.core.exceptions import NON_FIELD_ERRORS
 from django.core.files.uploadedfile import SimpleUploadedFile
 from django.core.validators import RegexValidator
 from django.forms import (
@@ -739,6 +740,39 @@ class FormsTestCase(TestCase):
         with six.assertRaisesRegex(self, ValueError, "has no field named"):
             f.add_error('missing_field', 'Some error.')
 
+    def test_has_error(self):
+        class UserRegistration(Form):
+            username = CharField(max_length=10)
+            password1 = CharField(widget=PasswordInput, min_length=5)
+            password2 = CharField(widget=PasswordInput)
+
+            def clean(self):
+                if (self.cleaned_data.get('password1') and self.cleaned_data.get('password2')
+                        and self.cleaned_data['password1'] != self.cleaned_data['password2']):
+                    raise ValidationError(
+                        'Please make sure your passwords match.',
+                        code='password_mismatch',
+                    )
+
+        f = UserRegistration(data={})
+        self.assertTrue(f.has_error('password1'))
+        self.assertTrue(f.has_error('password1', 'required'))
+        self.assertFalse(f.has_error('password1', 'anything'))
+
+        f = UserRegistration(data={'password1': 'Hi', 'password2': 'Hi'})
+        self.assertTrue(f.has_error('password1'))
+        self.assertTrue(f.has_error('password1', 'min_length'))
+        self.assertFalse(f.has_error('password1', 'anything'))
+        self.assertFalse(f.has_error('password2'))
+        self.assertFalse(f.has_error('password2', 'anything'))
+
+        f = UserRegistration(data={'password1': 'Bonjour', 'password2': 'Hello'})
+        self.assertFalse(f.has_error('password1'))
+        self.assertFalse(f.has_error('password1', 'required'))
+        self.assertTrue(f.has_error(NON_FIELD_ERRORS))
+        self.assertTrue(f.has_error(NON_FIELD_ERRORS, 'password_mismatch'))
+        self.assertFalse(f.has_error(NON_FIELD_ERRORS, 'anything'))
+
     def test_dynamic_construction(self):
         # It's possible to construct a Form dynamically by adding to the self.fields
         # dictionary in __init__(). Don't forget to call Form.__init__() within the