More informative error for invalid values passed to `|richtext` (#4971)

Fixes #4958

CHANGELOG.txt

@@ -4,6 +4,7 @@ Changelog
 2.5 (xx.xx.xxxx) - IN DEVELOPMENT
 ~~~~~~~~~~~~~~~~
 
+ * Added more informative error message when `|richtext` filter is applied to a non-string value (mukesh5)
  * Fix: Set `SERVER_PORT` to 443 in `Page.dummy_request()` for HTTPS sites (Sergey Fedoseev)
  * Fix: Validation error messages in `InlinePanel` no longer count towards `max_num` when disabling the 'add' button (Todd Dembrey, Thibaud Colas)
 

CONTRIBUTORS.rst

@@ -337,6 +337,7 @@ Contributors
 * Nick Travis
 * Maylon Pedroso
 * Thijs Walcarius
+* mukesh5
 
 Translators
 ===========

docs/releases/2.5.rst

@@ -14,6 +14,8 @@ What's new
 Other features
 ~~~~~~~~~~~~~~
 
+ * Added more informative error message when ``|richtext`` filter is applied to a non-string value (mukesh5)
+
 
 Bug fixes
 ~~~~~~~~~

wagtail/core/templatetags/wagtailcore_tags.py

@@ -87,7 +87,10 @@ def richtext(value):
     elif value is None:
         html = ''
     else:
-        html = expand_db_html(value)
+        if isinstance(value, str):
+            html = expand_db_html(value)
+        else:
+            raise TypeError("'richtext' template filter received an invalid value; expected string, got {}.".format(type(value)))
 
     return mark_safe('<div class="rich-text">' + html + '</div>')
 

wagtail/core/tests/tests.py

@@ -261,3 +261,11 @@ class TestRichtextTag(TestCase):
     def test_call_with_none(self):
         result = richtext(None)
         self.assertEqual(result, '<div class="rich-text"></div>')
+
+    def test_call_with_invalid_value(self):
+        with self.assertRaisesRegex(TypeError, "'richtext' template filter received an invalid value"):
+            richtext(42)
+
+    def test_call_with_bytes(self):
+        with self.assertRaisesRegex(TypeError, "'richtext' template filter received an invalid value"):
+            richtext(b"Hello world!")