Fixed #17413 -- Serialization of form errors along with all metadata.

django/contrib/admin/helpers.py

@@ -329,6 +329,8 @@ class AdminErrorList(forms.utils.ErrorList):
     Stores all errors for the form/formsets in an add/change stage view.
     """
     def __init__(self, form, inline_formsets):
+        super(AdminErrorList, self).__init__()
+
         if form.is_bound:
             self.extend(list(six.itervalues(form.errors)))
             for inline_formset in inline_formsets:

django/forms/fields.py

@@ -15,7 +15,7 @@ from io import BytesIO
 
 from django.core import validators
 from django.core.exceptions import ValidationError
-from django.forms.utils import ErrorList, from_current_timezone, to_current_timezone
+from django.forms.utils import from_current_timezone, to_current_timezone
 from django.forms.widgets import (
     TextInput, NumberInput, EmailInput, URLInput, HiddenInput,
     MultipleHiddenInput, ClearableFileInput, CheckboxInput, Select,
@@ -998,7 +998,7 @@ class MultiValueField(Field):
         DateField.clean(value[0]) and TimeField.clean(value[1]).
         """
         clean_data = []
-        errors = ErrorList()
+        errors = []
         if not value or isinstance(value, (list, tuple)):
             if not value or not [v for v in value if v not in self.empty_values]:
                 if self.required:

django/forms/forms.py

@@ -321,9 +321,9 @@ class BaseForm(object):
                     "argument contains errors for multiple fields."
                 )
             else:
-                error = dict(error)
+                error = error.error_dict
         else:
-            error = {field or NON_FIELD_ERRORS: list(error)}
+            error = {field or NON_FIELD_ERRORS: error.error_list}
 
         for field, error_list in error.items():
             if field not in self.errors:

django/forms/formsets.py

@@ -341,7 +341,7 @@ class BaseFormSet(object):
             # Give self.clean() a chance to do cross-form validation.
             self.clean()
         except ValidationError as e:
-            self._non_form_errors = self.error_class(e.messages)
+            self._non_form_errors = self.error_class(e.error_list)
 
     def clean(self):
         """

django/forms/utils.py

@@ -1,5 +1,7 @@
 from __future__ import unicode_literals
 
+import json
+import sys
 import warnings
 
 from django.conf import settings
@@ -8,12 +10,16 @@ from django.utils.encoding import force_text, python_2_unicode_compatible
 from django.utils import timezone
 from django.utils.translation import ugettext_lazy as _
 from django.utils import six
-import sys
 
 # Import ValidationError so that it can be imported from this
 # module to maintain backwards compatibility.
 from django.core.exceptions import ValidationError
 
+try:
+    from collections import UserList
+except ImportError:  # Python 2
+    from UserList import UserList
+
 
 def flatatt(attrs):
     """
@@ -46,8 +52,12 @@ class ErrorDict(dict):
 
     The dictionary keys are the field names, and the values are the errors.
     """
-    def __str__(self):
+    def as_data(self):
-        return self.as_ul()
+        return {f: e.as_data() for f, e in self.items()}
+
+    def as_json(self):
+        errors = {f: json.loads(e.as_json()) for f, e in self.items()}
+        return json.dumps(errors)
 
     def as_ul(self):
         if not self:
@@ -58,19 +68,35 @@ class ErrorDict(dict):
         )
 
     def as_text(self):
-        return '\n'.join('* %s\n%s' % (k, '\n'.join('  * %s' % force_text(i) for i in v)) for k, v in self.items())
+        output = []
+        for field, errors in self.items():
+            output.append('* %s' % field)
+            output.append('\n'.join('  * %s' % e for e in errors))
+        return '\n'.join(output)
 
-
-@python_2_unicode_compatible
-class ErrorList(list):
-    """
-    A collection of errors that knows how to display itself in various formats.
-    """
     def __str__(self):
         return self.as_ul()
 
+
+@python_2_unicode_compatible
+class ErrorList(UserList):
+    """
+    A collection of errors that knows how to display itself in various formats.
+    """
+    def as_data(self):
+        return self.data
+
+    def as_json(self):
+        errors = []
+        for error in ValidationError(self.data).error_list:
+            errors.append({
+                'message': list(error)[0],
+                'code': error.code or '',
+            })
+        return json.dumps(errors)
+
     def as_ul(self):
-        if not self:
+        if not self.data:
             return ''
         return format_html(
             '<ul class="errorlist">{0}</ul>',
@@ -78,12 +104,28 @@ class ErrorList(list):
         )
 
     def as_text(self):
-        if not self:
+        return '\n'.join('* %s' % e for e in self)
-            return ''
+
-        return '\n'.join('* %s' % force_text(e) for e in self)
+    def __str__(self):
+        return self.as_ul()
 
     def __repr__(self):
-        return repr([force_text(e) for e in self])
+        return repr(list(self))
+
+    def __contains__(self, item):
+        return item in list(self)
+
+    def __eq__(self, other):
+        return list(self) == other
+
+    def __ne__(self, other):
+        return list(self) != other
+
+    def __getitem__(self, i):
+        error = self.data[i]
+        if isinstance(error, ValidationError):
+            return list(error)[0]
+        return force_text(error)
 
 
 # Utilities for time zone support in DateTimeField et al.

docs/ref/forms/api.txt

@@ -117,6 +117,27 @@ The validation routines will only get called once, regardless of how many times
 you access :attr:`~Form.errors` or call :meth:`~Form.is_valid`. This means that
 if validation has side effects, those side effects will only be triggered once.
 
+.. method:: Form.errors.as_data()
+
+.. versionadded:: 1.7
+
+Returns a ``dict`` that maps fields to their original ``ValidationError``
+instances.
+
+    >>> f.errors.as_data()
+    {'sender': [ValidationError(['Enter a valid email address.'])],
+    'subject': [ValidationError(['This field is required.'])]}
+
+.. method:: Form.errors.as_json()
+
+.. versionadded:: 1.7
+
+Returns the errors serialized as JSON.
+
+    >>> f.errors.as_json()
+    {"sender": [{"message": "Enter a valid email address.", "code": "invalid"}],
+    "subject": [{"message": "This field is required.", "code": "required"}]}
+
 .. method:: Form.add_error(field, error)
 
 .. versionadded:: 1.7

docs/releases/1.7.txt

@@ -353,6 +353,12 @@ Forms
 * The new :meth:`~django.forms.Form.add_error()` method allows adding errors
   to specific form fields.
 
+* The dict-like attribute :attr:`~django.forms.Form.errors` now has two new
+  methods :meth:`~django.forms.Form.errors.as_data()` and
+  :meth:`~django.forms.Form.errors.as_json()`. The former returns a ``dict``
+  that maps fields to their original errors, complete with all metadata
+  (error code and params), the latter returns the errors serialized as json.
+
 Internationalization
 ^^^^^^^^^^^^^^^^^^^^
 

tests/forms_tests/tests/test_forms.py

@@ -3,6 +3,7 @@ from __future__ import unicode_literals
 
 import copy
 import datetime
+import json
 import warnings
 
 from django.core.files.uploadedfile import SimpleUploadedFile
@@ -2031,3 +2032,40 @@ class FormsTestCase(TestCase):
 
         form = SomeForm()
         self.assertHTMLEqual(form.as_p(), '<p id="p_some_field"></p>')
+
+    def test_error_dict(self):
+        class MyForm(Form):
+            foo = CharField()
+            bar = CharField()
+
+            def clean(self):
+                raise ValidationError('Non-field error.', code='secret', params={'a': 1, 'b': 2})
+
+        form = MyForm({})
+        self.assertEqual(form.is_valid(), False)
+
+        errors = form.errors.as_text()
+        control = [
+            '* foo\n  * This field is required.',
+            '* bar\n  * This field is required.',
+            '* __all__\n  * Non-field error.',
+        ]
+        for error in control:
+            self.assertIn(error, errors)
+
+        errors = form.errors.as_ul()
+        control = [
+            '<li>foo<ul class="errorlist"><li>This field is required.</li></ul></li>',
+            '<li>bar<ul class="errorlist"><li>This field is required.</li></ul></li>',
+            '<li>__all__<ul class="errorlist"><li>Non-field error.</li></ul></li>',
+        ]
+        for error in control:
+            self.assertInHTML(error, errors)
+
+        errors = json.loads(form.errors.as_json())
+        control = {
+            'foo': [{'code': 'required', 'message': 'This field is required.'}],
+            'bar': [{'code': 'required', 'message': 'This field is required.'}],
+            '__all__': [{'code': 'secret', 'message': 'Non-field error.'}]
+        }
+        self.assertEqual(errors, control)