When customers call our JSON:API API, they can use an "include" parameter
to specify related objects to be appended to the response.
However, requests to include are not always satisfiable (e.g. if
job.supervisor=null, include=supervisor is ignored).
In order to prevent Marshmallow from trying to load nonexistent related
objects to append to our API responses, we need to tell it when to ignore a
relationship attribute, such as via setting
job.supervisor=marshmallow.missing (if it sees job.supervisor=None, it will
attempt (and fail) to load the null supervisor object, so we cannot just
leave it as-is).
Unfortunately, this causes problems as SQLAlchemy attempts to handle the
new value:
Error Traceback (most recent call last): File
"/Users/lucadou/IdeaProjects/person-api/api/unit_tests/test_person_service.py",
line 601, in test_get_people_include_job response =
self.person_service.get_people(QueryParameters({"include": "jobs"}))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/src/person_service.py", line
61, in get_people response = person_schema.dump(people, many=True)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/marshmallow/schema.py",
line 557, in dump result = self._serialize(processed_obj, many=many)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/marshmallow/schema.py",
line 519, in _serialize return [ ^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/marshmallow/schema.py",
line 520, in <listcomp> self._serialize(d, many=False) File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/marshmallow/schema.py",
line 525, in _serialize value = field_obj.serialize(attr_name, obj,
accessor=self.get_attribute)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/marshmallow_jsonapi/fields.py",
line 248, in serialize return super().serialize(attr, obj, accessor)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/marshmallow/fields.py",
line 344, in serialize return self._serialize(value, attr, obj, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/marshmallow_jsonapi/fields.py",
line 274, in _serialize self._serialize_included(item) File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/marshmallow_jsonapi/fields.py",
line 280, in _serialize_included result = self.schema.dump(value)
^^^^^^^^^^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/marshmallow/schema.py",
line 551, in dump processed_obj = self._invoke_dump_processors(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/marshmallow/schema.py",
line 1068, in _invoke_dump_processors data = self._invoke_processors(
^^^^^^^^^^^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/marshmallow/schema.py",
line 1225, in _invoke_processors data = processor(data, many=many, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/src/model/schema/job_schema.py",
line 62, in set_null_supervisor job.supervisor = missing ^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/sqlalchemy/orm/attributes.py",
line 536, in __set__ self.impl.set( File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/sqlalchemy/orm/attributes.py",
line 1466, in set value = self.fire_replace_event(state, dict_, value, old,
initiator) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/sqlalchemy/orm/attributes.py",
line 1505, in fire_replace_event value = fn( ^^^ File
"/Users/lucadou/IdeaProjects/person-api/api/venv/lib/python3.11/site-packages/sqlalchemy/orm/attributes.py",
line 2167, in emit_backref_from_scalar_set_event instance_state(child),
^^^^^^^^^^^^^^^^^^^^^ AttributeError: '_Missing' object has no attribute
'_sa_instance_state'
Is there any way to temporarily disable ORM event listeners when we mutate
objects and have no intention of saving the changes/do not intend for the
ORM to act on them?
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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