Merge pull request #176 from fuhrysteve/nested_lambda

🐛 Fix `AttributeError` when nesting schemas using `lambda: Schema()`

marshmallow_jsonschema/base.py

@@ -159,7 +159,10 @@ def get_properties(self, obj) -> typing.Dict[str, typing.Dict[str, typing.Any]]:
         if self.props_ordered:
             fields_items_sequence = obj.fields.items()
         else:
-            fields_items_sequence = sorted(obj.fields.items())
+            if callable(obj):
+                fields_items_sequence = sorted(obj().fields.items())
+            else:
+                fields_items_sequence = sorted(obj.fields.items())
 
         for field_name, field in fields_items_sequence:
             schema = self._get_schema_for_field(obj, field)
@@ -172,8 +175,11 @@ def get_properties(self, obj) -> typing.Dict[str, typing.Dict[str, typing.Any]]:
     def get_required(self, obj) -> typing.Union[typing.List[str], _Missing]:
         """Fill out required field."""
         required = []
-
-        for field_name, field in sorted(obj.fields.items()):
+        if callable(obj):
+            field_items_iterable = sorted(obj().fields.items())
+        else:
+            field_items_iterable = sorted(obj.fields.items())
+        for field_name, field in field_items_iterable:
             if field.required:
                 required.append(field.data_key or field.name)
 
@@ -294,6 +300,11 @@ def _from_nested_schema(self, obj, field):
             exclude = field.exclude
             nested_cls = nested
             nested_instance = nested(only=only, exclude=exclude, context=obj.context)
+        elif callable(nested):
+            nested_instance = nested()
+            nested_type = type(nested_instance)
+            name = nested_type.__name__
+            nested_cls = nested_type.__class__
         else:
             nested_cls = nested.__class__
             name = nested_cls.__name__

tests/test_dump.py

@@ -744,3 +744,30 @@ class TestSchema(Schema):
     assert (
         len(data["definitions"]["TestSchema"]["properties"]["union_prop"]["anyOf"]) == 3
     )
+
+
+def test_dumping_recursive_schema():
+    """
+    this reproduces issue https://github.com/fuhrysteve/marshmallow-jsonschema/issues/164
+    """
+    json_schema = JSONSchema()
+
+    def generate_recursive_schema_with_name():
+        class RecursiveSchema(Schema):
+            # when nesting recursively you can either refer the recursive schema by its name
+            nested_mwe_recursive = fields.Nested("RecursiveSchema")
+
+        return json_schema.dump(RecursiveSchema())
+
+    def generate_recursive_schema_with_lambda():
+        class RecursiveSchema(Schema):
+            # or you can use a lambda (as suggested in the marshmallow docs)
+            nested_mwe_recursive = fields.Nested(lambda: RecursiveSchema())
+
+        return json_schema.dump(
+            RecursiveSchema()
+        )  # this shall _not_ raise an AttributeError
+
+    lambda_schema = generate_recursive_schema_with_lambda()
+    name_schema = generate_recursive_schema_with_name()
+    assert lambda_schema == name_schema