[1.9.x] Fixed #25532 -- Properly redisplayed JSONField form input values

Thanks David Szotten for the report and Tommy Beadle for code inspiration.
Thanks Tim Graham for the review.
Partial backport of db19619545 from master.

django/contrib/postgres/forms/jsonb.py

@@ -1,11 +1,16 @@
 import json
 
 from django import forms
+from django.utils import six
 from django.utils.translation import ugettext_lazy as _
 
 __all__ = ['JSONField']
 
 
+class InvalidJSONInput(six.text_type):
+    pass
+
+
 class JSONField(forms.CharField):
     default_error_messages = {
         'invalid': _("'%(value)s' value must be valid JSON."),
@@ -27,5 +32,15 @@ class JSONField(forms.CharField):
                 params={'value': value},
             )
 
+    def bound_data(self, data, initial):
+        if self.disabled:
+            return initial
+        try:
+            return json.loads(data)
+        except ValueError:
+            return InvalidJSONInput(data)
+
     def prepare_value(self, value):
+        if isinstance(value, InvalidJSONInput):
+            return value
         return json.dumps(value)

docs/releases/1.9.5.txt

@@ -46,3 +46,6 @@ Bugfixes
 
 * Fixed a migrations crash on SQLite when renaming the primary key of a model
   containing a ``ForeignKey`` to ``'self'`` (:ticket:`26384`).
+
+* Fixed ``JSONField`` inadvertently escaping its contents when displaying values
+  after failed form validation (:ticket:`25532`).

tests/postgres_tests/test_json.py

@@ -3,7 +3,9 @@ import unittest
 
 from django.core import exceptions, serializers
 from django.db import connection
+from django.forms import CharField, Form
 from django.test import TestCase
+from django.utils.html import escape
 
 from . import PostgreSQLTestCase
 from .models import JSONModel
@@ -258,7 +260,34 @@ class TestFormField(PostgreSQLTestCase):
         form_field = model_field.formfield()
         self.assertIsInstance(form_field, forms.JSONField)
 
+    def test_formfield_disabled(self):
+        class JsonForm(Form):
+            name = CharField()
+            jfield = forms.JSONField(disabled=True)
+
+        form = JsonForm({'name': 'xyz', 'jfield': '["bar"]'}, initial={'jfield': ['foo']})
+        self.assertIn('[&quot;foo&quot;]</textarea>', form.as_p())
+
     def test_prepare_value(self):
         field = forms.JSONField()
         self.assertEqual(field.prepare_value({'a': 'b'}), '{"a": "b"}')
         self.assertEqual(field.prepare_value(None), 'null')
+        self.assertEqual(field.prepare_value('foo'), '"foo"')
+
+    def test_redisplay_wrong_input(self):
+        """
+        When displaying a bound form (typically due to invalid input), the form
+        should not overquote JSONField inputs.
+        """
+        class JsonForm(Form):
+            name = CharField(max_length=2)
+            jfield = forms.JSONField()
+
+        # JSONField input is fine, name is too long
+        form = JsonForm({'name': 'xyz', 'jfield': '["foo"]'})
+        self.assertIn('[&quot;foo&quot;]</textarea>', form.as_p())
+
+        # This time, the JSONField input is wrong
+        form = JsonForm({'name': 'xy', 'jfield': '{"foo"}'})
+        # Appears once in the textarea and once in the error message
+        self.assertEqual(form.as_p().count(escape('{"foo"}')), 2)