[2.0.x] Fixed #29109 -- Fixed the admin time picker widget for the Thai locale.

Backport of 1a1264f1494976c562c7cb832fe47f3e1e765b8f from master

3 files changed, 23 insertions, 2 deletions

diff --git a/django/conf/locale/th/formats.py b/django/conf/locale/th/formats.py
index d4f478e0c1..5a980f097c 100644
--- a/django/conf/locale/th/formats.py
+++ b/django/conf/locale/th/formats.py
@@ -19,13 +19,13 @@ DATE_INPUT_FORMATS = [
     '%d %B %Y',  # 25 ตุลาคม 2006
 ]
 TIME_INPUT_FORMATS = [
-    '%H:%M:%S.%f',  # 14:30:59.000200
     '%H:%M:%S',  # 14:30:59
+    '%H:%M:%S.%f',  # 14:30:59.000200
     '%H:%M',  # 14:30
 ]
 DATETIME_INPUT_FORMATS = [
-    '%d/%m/%Y %H:%M:%S.%f',  # 25/10/2006 14:30:59.000200
     '%d/%m/%Y %H:%M:%S',  # 25/10/2006 14:30:59
+    '%d/%m/%Y %H:%M:%S.%f',  # 25/10/2006 14:30:59.000200
     '%d/%m/%Y %H:%M',  # 25/10/2006 14:30
 ]
 DECIMAL_SEPARATOR = '.'
diff --git a/docs/releases/2.0.3.txt b/docs/releases/2.0.3.txt
index 4fbca2e247..277cab7573 100644
--- a/docs/releases/2.0.3.txt
+++ b/docs/releases/2.0.3.txt
@@ -11,3 +11,7 @@ Bugfixes
 
 * Fixed a regression that caused sliced ``QuerySet.distinct().order_by()``
   followed by ``count()`` to crash (:ticket:`29108`).
+
+* Prioritized the datetime and time input formats without ``%f`` for the Thai
+  locale to fix the admin time picker widget displaying "undefined"
+  (:ticket:`29109`).
diff --git a/tests/i18n/tests.py b/tests/i18n/tests.py
index 83e2260a51..4e35391a83 100644
--- a/tests/i18n/tests.py
+++ b/tests/i18n/tests.py
@@ -3,6 +3,7 @@ import decimal
 import gettext as gettext_module
 import os
 import pickle
+import re
 from contextlib import contextmanager
 from importlib import import_module
 from threading import local
@@ -1091,6 +1092,22 @@ class FormattingTests(SimpleTestCase):
             with translation.override('fr', deactivate=True):
                 self.assertEqual('d/m/Y CUSTOM', get_format('CUSTOM_DAY_FORMAT'))
 
+    def test_admin_javascript_supported_input_formats(self):
+        """
+        The first input format for DATE_INPUT_FORMATS, TIME_INPUT_FORMATS, and
+        DATETIME_INPUT_FORMATS must not contain %f since that's unsupported by
+        the admin's time picker widget.
+        """
+        regex = re.compile('%([^BcdHImMpSwxXyY%])')
+        for language_code, language_name in settings.LANGUAGES:
+            for format_name in ('DATE_INPUT_FORMATS', 'TIME_INPUT_FORMATS', 'DATETIME_INPUT_FORMATS'):
+                with self.subTest(language=language_code, format=format_name):
+                    formatter = get_format(format_name, lang=language_code)[0]
+                    self.assertEqual(
+                        regex.findall(formatter), [],
+                        "%s locale's %s uses an unsupported format code." % (language_code, format_name)
+                    )
+
 
 class MiscTests(SimpleTestCase):