René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"New behavior around optional nested objects breaks deserialization when explicit null is returned","articleBody":"**Describe the bug**\r\nWe use FastAPI as an API server and generate a python client with `open-api-client` that is then used to run integration tests.  Our team is using 0.7.3 but I was trying to update to 0.8.0.  When doing so, we ran into the following exception running our test suite:\r\n```\r\n/usr/local/lib/python3.8/site-packages/falkon_sdk/api/observations/get_observations.py:73: in _parse_response\r\n    response_200 = ObservationResult.from_dict(response.json())\r\n/usr/local/lib/python3.8/site-packages/falkon_sdk/models/observation_result.py:104: in from_dict\r\n    metric_change = ObservationFactWindowSummaryResource.from_dict(\r\n/usr/local/lib/python3.8/site-packages/falkon_sdk/models/observation_fact_window_summary_resource.py:156: in from_dict\r\n    weighted_change_unfiltered = WeightedChange.from_dict(\r\n_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ \r\n\r\ncls = \u003cclass 'falkon_sdk.models.weighted_change.WeightedChange'\u003e\r\nsrc_dict = None\r\n\r\n    @classmethod\r\n    def from_dict(cls: Type[T], src_dict: Dict[str, Any]) -\u003e T:\r\n\u003e       d = src_dict.copy()\r\nE       AttributeError: 'NoneType' object has no attribute 'copy'\r\n```\r\n\r\nI was able to narrow down the problem to handling of `Optional[T]` objects within response models.  Here is a minimal repro:\r\n\r\n**To Reproduce**\r\nSteps to reproduce the behavior:\r\n1. Make a main.py file with the following contents:\r\n```\r\nfrom typing import Optional\r\nfrom fastapi import FastAPI\r\nfrom pydantic import BaseModel\r\n\r\napp = FastAPI()\r\n\r\nclass ItemResource(BaseModel):\r\n    id: int\r\n\r\nclass ResourceWithOptional(BaseModel):\r\n    item: Optional[ItemResource]\r\n\r\n@app.get(\"/\", response_model=ResourceWithOptional)\r\ndef read_item():\r\n    return ResourceWithOptional(item=None)\r\n```\r\n2.  Start it up in uvicorn\r\n```\r\nuvicorn main:app \u0026\r\n```\r\n2.  Curling that endpoint returns this:\r\n```\r\ncurl -s http://localhost:8000/\r\nINFO:     127.0.0.1:32770 - \"GET / HTTP/1.1\" 200 OK\r\n{\"item\":null}\r\n```\r\n\r\n3.  Generate a client for this:\r\n```\r\nopenapi-python-client generate --url http://localhost:8000/openapi.json\r\n```\r\n\r\n4.  Look at the generated `resource_with_optional.py` in the `from_dict` method:\r\n```\r\n        item: Union[ItemResource, Unset] = UNSET\r\n        _item = d.pop(\"item\", UNSET)\r\n        if not isinstance(_item, Unset):\r\n            item = ItemResource.from_dict(_item)\r\n```\r\n\r\n**Expected behavior**\r\nI expect that this allows for an explicit `null` to be returned, as was the case in openapi-python-client==0.7.3, where the generated code looks like this:\r\n```\r\n        item: Union[ItemResource, Unset] = UNSET\r\n        _item = d.pop(\"item\", UNSET)\r\n        if _item is not None and not isinstance(_item, Unset):\r\n            item = ItemResource.from_dict(cast(Dict[str, Any], _item))\r\n```\r\n\r\n**OpenAPI Spec File**\r\n```\r\n{\"openapi\":\"3.0.2\",\"info\":{\"title\":\"FastAPI\",\"version\":\"0.1.0\"},\"paths\":{\"/\":{\"get\":{\"summary\":\"Read Item\",\"operationId\":\"read_item__get\",\"responses\":{\"200\":{\"description\":\"Successful Response\",\"content\":{\"application/json\":{\"schema\":{\"$ref\":\"#/components/schemas/ResourceWithOptional\"}}}}}}}},\"components\":{\"schemas\":{\"ItemResource\":{\"title\":\"ItemResource\",\"required\":[\"id\"],\"type\":\"object\",\"properties\":{\"id\":{\"title\":\"Id\",\"type\":\"integer\"}}},\"ResourceWithOptional\":{\"title\":\"ResourceWithOptional\",\"type\":\"object\",\"properties\":{\"item\":{\"$ref\":\"#/components/schemas/ItemResource\"}}}}}}\r\n```\r\n\r\n**Desktop (please complete the following information):**\r\n - OS: Ubuntu Linux 20.04\r\n - Python Version: 3.8.6\r\n - openapi-python-client version 0.8.0\r\n\r\n**Additional context**\r\nFastAPI has support for excluding nulls from responses with `response_model_exclude_none` but this means changing how our API works to suit the sdk generator, which I would prefer not to have to do.\r\nThe new behavior I was referring to seems to have come in with #334 \r\n","author":{"url":"https://github.com/joshzana","@type":"Person","name":"joshzana"},"datePublished":"2021-03-03T05:48:49.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/343/openapi-python-client/issues/343"}