OpenAPI schemas: Ensure lazy field descriptions are converted to str(). (#6832)

rest_framework/schemas/openapi.py

@@ -377,7 +377,7 @@ class AutoSchema(ViewInspector):
             if field.default and field.default != empty:  # why don't they use None?!
                 schema['default'] = field.default
             if field.help_text:
-                schema['description'] = field.help_text
+                schema['description'] = str(field.help_text)
             self._map_field_validators(field.validators, schema)
 
             properties[field.field_name] = schema

tests/schemas/test_openapi.py

@@ -1,6 +1,7 @@
 import pytest
 from django.conf.urls import url
 from django.test import RequestFactory, TestCase, override_settings
+from django.utils.translation import gettext_lazy as _
 
 from rest_framework import filters, generics, pagination, routers, serializers
 from rest_framework.compat import uritemplate
@@ -52,6 +53,15 @@ class TestFieldMapping(TestCase):
             with self.subTest(field=field):
                 assert inspector._map_field(field) == mapping
 
+    def test_lazy_string_field(self):
+        class Serializer(serializers.Serializer):
+            text = serializers.CharField(help_text=_('lazy string'))
+
+        inspector = AutoSchema()
+
+        data = inspector._map_serializer(Serializer())
+        assert isinstance(data['properties']['text']['description'], str), "description must be str"
+
 
 @pytest.mark.skipif(uritemplate is None, reason='uritemplate not installed.')
 class TestOperationIntrospection(TestCase):