1 files changed, 68 insertions, 3 deletions
diff --git a/django/forms/fields.py b/django/forms/fields.py
index c5374c7e9d..36dad72704 100644
--- a/django/forms/fields.py
+++ b/django/forms/fields.py
@@ -4,6 +4,7 @@ Field classes.
 
 import copy
 import datetime
+import json
 import math
 import operator
 import os
@@ -21,8 +22,8 @@ from django.forms.widgets import (
     FILE_INPUT_CONTRADICTION, CheckboxInput, ClearableFileInput, DateInput,
     DateTimeInput, EmailInput, FileInput, HiddenInput, MultipleHiddenInput,
     NullBooleanSelect, NumberInput, Select, SelectMultiple,
-    SplitDateTimeWidget, SplitHiddenDateTimeWidget, TextInput, TimeInput,
-    URLInput,
+    SplitDateTimeWidget, SplitHiddenDateTimeWidget, Textarea, TextInput,
+    TimeInput, URLInput,
 )
 from django.utils import formats
 from django.utils.dateparse import parse_datetime, parse_duration
@@ -38,7 +39,8 @@ __all__ = (
     'BooleanField', 'NullBooleanField', 'ChoiceField', 'MultipleChoiceField',
     'ComboField', 'MultiValueField', 'FloatField', 'DecimalField',
     'SplitDateTimeField', 'GenericIPAddressField', 'FilePathField',
-    'SlugField', 'TypedChoiceField', 'TypedMultipleChoiceField', 'UUIDField',
+    'JSONField', 'SlugField', 'TypedChoiceField', 'TypedMultipleChoiceField',
+    'UUIDField',
 )
 
 
@@ -1211,3 +1213,66 @@ class UUIDField(CharField):
             except ValueError:
                 raise ValidationError(self.error_messages['invalid'], code='invalid')
         return value
+
+
+class InvalidJSONInput(str):
+    pass
+
+
+class JSONString(str):
+    pass
+
+
+class JSONField(CharField):
+    default_error_messages = {
+        'invalid': _('Enter a valid JSON.'),
+    }
+    widget = Textarea
+
+    def __init__(self, encoder=None, decoder=None, **kwargs):
+        self.encoder = encoder
+        self.decoder = decoder
+        super().__init__(**kwargs)
+
+    def to_python(self, value):
+        if self.disabled:
+            return value
+        if value in self.empty_values:
+            return None
+        elif isinstance(value, (list, dict, int, float, JSONString)):
+            return value
+        try:
+            converted = json.loads(value, cls=self.decoder)
+        except json.JSONDecodeError:
+            raise ValidationError(
+                self.error_messages['invalid'],
+                code='invalid',
+                params={'value': value},
+            )
+        if isinstance(converted, str):
+            return JSONString(converted)
+        else:
+            return converted
+
+    def bound_data(self, data, initial):
+        if self.disabled:
+            return initial
+        try:
+            return json.loads(data, cls=self.decoder)
+        except json.JSONDecodeError:
+            return InvalidJSONInput(data)
+
+    def prepare_value(self, value):
+        if isinstance(value, InvalidJSONInput):
+            return value
+        return json.dumps(value, cls=self.encoder)
+
+    def has_changed(self, initial, data):
+        if super().has_changed(initial, data):
+            return True
+        # For purposes of seeing whether something has changed, True isn't the
+        # same as 1 and the order of keys doesn't matter.
+        return (
+            json.dumps(initial, sort_keys=True, cls=self.encoder) !=
+            json.dumps(self.to_python(data), sort_keys=True, cls=self.encoder)
+        )