[1.8.x] Fixed #14497 -- Improved admin widget for "read only" FileFields

Based on patch by Adam J Forster, Paul Collins, and Julien.

Backport of 2be621e44c from master

django/contrib/admin/utils.py

@@ -1,23 +1,22 @@
 from __future__ import unicode_literals
 
-from collections import defaultdict
 import datetime
 import decimal
+from collections import defaultdict
 
 from django.contrib.auth import get_permission_codename
 from django.core.exceptions import FieldDoesNotExist
+from django.core.urlresolvers import reverse, NoReverseMatch
 from django.db import models
 from django.db.models.constants import LOOKUP_SEP
 from django.db.models.deletion import Collector
 from django.forms.forms import pretty_name
-from django.utils import formats
+from django.utils import formats, six, timezone
-from django.utils.html import format_html
-from django.utils.text import capfirst
-from django.utils import timezone
 from django.utils.encoding import force_str, force_text, smart_text
-from django.utils import six
+from django.utils.html import conditional_escape, format_html
+from django.utils.safestring import mark_safe
+from django.utils.text import capfirst
 from django.utils.translation import ungettext
-from django.core.urlresolvers import reverse, NoReverseMatch
 
 
 def lookup_needs_distinct(opts, lookup_path):
@@ -389,6 +388,11 @@ def display_for_field(value, field):
         return formats.number_format(value, field.decimal_places)
     elif isinstance(field, models.FloatField):
         return formats.number_format(value)
+    elif isinstance(field, models.FileField):
+        return mark_safe('<a href="%s">%s</a>' % (
+            conditional_escape(value.url),
+            conditional_escape(value),
+        ))
     else:
         return smart_text(value)
 

tests/admin_widgets/tests.py

@@ -350,26 +350,55 @@ class AdminURLWidgetTest(DjangoTestCase):
         )
 
 
-class AdminFileWidgetTest(DjangoTestCase):
+@override_settings(
-    def test_render(self):
+    PASSWORD_HASHERS=['django.contrib.auth.hashers.SHA1PasswordHasher'],
+    ROOT_URLCONF='admin_widgets.urls',
+)
+class AdminFileWidgetTests(DjangoTestCase):
+    fixtures = ['admin-widgets-users.xml']
+
+    def setUp(self):
         band = models.Band.objects.create(name='Linkin Park')
-        album = band.album_set.create(
+        self.album = band.album_set.create(
             name='Hybrid Theory', cover_art=r'albums\hybrid_theory.jpg'
         )
 
+    def test_render(self):
         w = widgets.AdminFileWidget()
         self.assertHTMLEqual(
-            w.render('test', album.cover_art),
+            w.render('test', self.album.cover_art),
-            '<p class="file-upload">Currently: <a href="%(STORAGE_URL)salbums/hybrid_theory.jpg">albums\hybrid_theory.jpg</a> <span class="clearable-file-input"><input type="checkbox" name="test-clear" id="test-clear_id" /> <label for="test-clear_id">Clear</label></span><br />Change: <input type="file" name="test" /></p>' % {
+            '<p class="file-upload">Currently: <a href="%(STORAGE_URL)salbums/'
-                'STORAGE_URL': default_storage.url('')
+            'hybrid_theory.jpg">albums\hybrid_theory.jpg</a> '
+            '<span class="clearable-file-input">'
+            '<input type="checkbox" name="test-clear" id="test-clear_id" /> '
+            '<label for="test-clear_id">Clear</label></span><br />'
+            'Change: <input type="file" name="test" /></p>' % {
+                'STORAGE_URL': default_storage.url(''),
             },
         )
-
         self.assertHTMLEqual(
             w.render('test', SimpleUploadedFile('test', b'content')),
             '<input type="file" name="test" />',
         )
 
+    def test_readonly_fields(self):
+        """
+        File widgets should render as a link when they're marked "read only."
+        """
+        self.client.login(username="super", password="secret")
+        response = self.client.get('/admin_widgets/album/%s/' % self.album.id)
+        self.assertContains(
+            response,
+            '<p><a href="%(STORAGE_URL)salbums/hybrid_theory.jpg">'
+            'albums\hybrid_theory.jpg</a></p>' % {'STORAGE_URL': default_storage.url('')},
+            html=True,
+        )
+        self.assertNotContains(
+            response,
+            '<input type="file" name="cover_art" id="id_cover_art" />',
+            html=True,
+        )
+
 
 @override_settings(ROOT_URLCONF='admin_widgets.urls')
 class ForeignKeyRawIdWidgetTest(DjangoTestCase):

tests/admin_widgets/widgetadmin.py

@@ -24,6 +24,11 @@ class EventAdmin(admin.ModelAdmin):
     raw_id_fields = ['main_band', 'supporting_bands']
 
 
+class AlbumAdmin(admin.ModelAdmin):
+    fields = ('name', 'cover_art',)
+    readonly_fields = ('cover_art',)
+
+
 class SchoolAdmin(admin.ModelAdmin):
     filter_vertical = ('students',)
     filter_horizontal = ('alumni',)
@@ -37,7 +42,7 @@ site.register(models.CarTire, CarTireAdmin)
 site.register(models.Member)
 site.register(models.Band)
 site.register(models.Event, EventAdmin)
-site.register(models.Album)
+site.register(models.Album, AlbumAdmin)
 
 site.register(models.Inventory)