Don't swallow TypeErrors raised by _bind_to_schema or on_bind_field (#1376)

Author: sloria

CHANGELOG.rst

@@ -1,6 +1,13 @@
 Changelog
 ---------
 
+2.20.3 (unreleased)
+*******************
+
+Bug fixes:
+
+- Don't swallow ``TypeError`` exceptions raised by ``Field._bind_to_schema`` or ``Schema.on_bind_field``.
+
 2.20.2 (2019-08-20)
 *******************
 

src/marshmallow/schema.py

@@ -786,14 +786,13 @@ def __set_field_attrs(self, fields_dict):
         specified in ``class Meta``.
         """
         for field_name, field_obj in iteritems(fields_dict):
+            if field_name in self.load_only:
+                field_obj.load_only = True
+            if field_name in self.dump_only:
+                field_obj.dump_only = True
             try:
-                if field_name in self.load_only:
-                    field_obj.load_only = True
-                if field_name in self.dump_only:
-                    field_obj.dump_only = True
                 field_obj._add_to_schema(field_name, self)
-                self.on_bind_field(field_name, field_obj)
-            except TypeError:
+            except TypeError as error:
                 # field declared as a class, not an instance
                 if (isinstance(field_obj, type) and
                         issubclass(field_obj, base.FieldABC)):
@@ -802,6 +801,8 @@ def __set_field_attrs(self, fields_dict):
                            'Did you mean "fields.{1}()"?'
                            .format(field_name, field_obj.__name__))
                     raise TypeError(msg)
+                raise error
+            self.on_bind_field(field_name, field_obj)
         return fields_dict
 
     def __filter_fields(self, field_names, obj, many=False):

tests/test_schema.py

@@ -552,6 +552,17 @@ class BadUserSchema(Schema):
     with pytest.raises(TypeError, match='must be declared as a Field instance'):
         BadUserSchema().dump(user)
 
+# regression test
+def test_bind_field_does_not_swallow_typeerror():
+    class MySchema(Schema):
+        name = fields.Str()
+
+        def on_bind_field(self, field_name, field_obj):
+            raise TypeError("boom")
+
+    with pytest.raises(TypeError, match="boom"):
+        MySchema()
+
 @pytest.mark.parametrize('SchemaClass',
     [UserSchema, UserMetaSchema])
 def test_serializing_generator(SchemaClass):