Improve handling of nullable Raw fields for OAS 3.1.0 (#961)

* Improved handling of nullable Raw fields for OAS 3.1.0

* Remove .gitignore entry

* Update changelog

---------

Co-authored-by: Tayler Sokalski <tsokalski@users.noreply.github.com>
Co-authored-by: Steven Loria <sloria1@gmail.com>

Author: tsokalski

CHANGELOG.rst

@@ -1,9 +1,14 @@
 Changelog
 ---------
 
-6.9.0 (unreleased)
+6.8.1 (unreleased)
 ******************
 
+Bug fixes:
+
+- Fix handling of nullable Raw fields for OAS 3.1.0 (:issue:`960`).
+  Thanks :user:`tsokalski` for reporting and fixing.
+
 Support:
 
 - Support marshmallow 4 (:pr:`963`).

src/apispec/ext/marshmallow/field_converter.py

@@ -318,7 +318,7 @@ def field2nullable(self, field: marshmallow.fields.Field, ret) -> dict:
                     attributes["anyOf"] = [{"$ref": ret.pop("$ref")}, {"type": "null"}]
                 elif "allOf" in ret:
                     attributes["anyOf"] = [*ret.pop("allOf"), {"type": "null"}]
-                else:
+                elif "type" in ret:
                     attributes["type"] = [*make_type_list(ret.get("type")), "null"]
         return attributes
 

tests/test_ext_marshmallow_field.py

@@ -197,6 +197,20 @@ def test_field_with_allow_none(spec_fixture):
         assert res["type"] == ["string", "null"]
 
 
+@pytest.mark.parametrize("spec_fixture", ("2.0", "3.0.0", "3.1.0"), indirect=True)
+@pytest.mark.parametrize("field_class", [fields.Field, fields.Raw])
+def test_nullable_field_with_no_type(spec_fixture, field_class):
+    field = field_class(allow_none=True)
+    res = spec_fixture.openapi.field2property(field)
+    if spec_fixture.openapi.openapi_version.major < 3:
+        assert res["x-nullable"] is True
+    elif spec_fixture.openapi.openapi_version.minor < 1:
+        assert res["nullable"] is True
+    else:
+        assert "nullable" not in res
+        assert "type" not in res
+
+
 @pytest.mark.parametrize("spec_fixture", ("2.0", "3.0.0", "3.1.0"), indirect=True)
 def test_nested_nullable(spec_fixture):
     class Child(Schema):