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.

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)

django/forms/forms.py

@@ -365,13 +365,14 @@ class BaseForm(object):
 
     def _clean_fields(self):
         for name, field in self.fields.items():
+            if field.disabled:
+                # Initial values are supposed to be clean
+                self.cleaned_data[name] = self.initial.get(name, field.initial)
+                continue
             # value_from_datadict() gets the data from the data dictionaries.
             # Each widget type knows how to retrieve its own data, because some
             # widgets split data over several HTML fields.
-            if field.disabled:
-                value = self.initial.get(name, field.initial)
-            else:
-                value = field.widget.value_from_datadict(self.data, self.files, self.add_prefix(name))
+            value = field.widget.value_from_datadict(self.data, self.files, self.add_prefix(name))
             try:
                 if isinstance(field, FileField):
                     initial = self.initial.get(name, field.initial)