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BlueapiClient gives unhelpful error message when invalid JSON is returned #1472
Description
When trying to use BlueapiClient, I got the following error message when trying to run the below:
from blueapi.client import BlueapiClient
bc = BlueapiClient.from_config_file("path/to/config.yaml")
devs = bc.devices
plans = bc.planspython -i /home/xol73553/Documents/BLUESKY/i09_blueapi.py
Traceback (most recent call last):
File "/scratch/bluesky_development/blueapi/venv/lib64/python3.12/site-packages/requests/models.py", line 976, in json
return complexjson.loads(self.text, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib64/python3.12/json/__init__.py", line 346, in loads
return _default_decoder.decode(s)
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib64/python3.12/json/decoder.py", line 338, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib64/python3.12/json/decoder.py", line 356, in raw_decode
raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/home/xol73553/Documents/BLUESKY/i09_blueapi.py", line 22, in <module>
devs = bc.devices
^^^^^^^^^^
File "/usr/lib64/python3.12/functools.py", line 998, in __get__
val = self.func(instance)
^^^^^^^^^^^^^^^^^^^
File "/scratch/bluesky_development/blueapi/venv/lib64/python3.12/site-packages/observability_utils/tracing/decorators.py", line 151, in wrapper
return func(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^
File "/scratch/bluesky_development/blueapi/src/blueapi/client/client.py", line 307, in devices
return DeviceCache(self._rest)
^^^^^^^^^^^^^^^^^^^^^^^
File "/scratch/bluesky_development/blueapi/src/blueapi/client/client.py", line 111, in __init__
for model in rest.get_devices().devices
^^^^^^^^^^^^^^^^^^
File "/scratch/bluesky_development/blueapi/src/blueapi/client/rest.py", line 162, in get_devices
return self._request_and_deserialize("/devices", DeviceResponse)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/scratch/bluesky_development/blueapi/venv/lib64/python3.12/site-packages/observability_utils/tracing/decorators.py", line 151, in wrapper
return func(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^
File "/scratch/bluesky_development/blueapi/src/blueapi/client/rest.py", line 290, in _request_and_deserialize
deserialized = TypeAdapter(target_type).validate_python(response.json())
^^^^^^^^^^^^^^^
File "/scratch/bluesky_development/blueapi/venv/lib64/python3.12/site-packages/requests/models.py", line 980, in json
raise RequestsJSONDecodeError(e.msg, e.doc, e.pos)
requests.exceptions.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
The response for devices contains no json, so it provides a JSONDecodeError. The reason the response provides no valid json was because I was not logged in any more.
>>> bc.login()
Logging in
Please login from this URL:- https://identity.diamond.ac.uk/realms/dls/device?user_code=ULED-SLXT
Logged in and cached new token
>>> exit()
Now rerunning the script
python -i /home/xol73553/Documents/BLUESKY/i09_blueapi.py
>>>
It works! But the error message above didn't indicate the issue is due to not being logged in.
Acceptance critera
The client should instead make a check to see if the user is logged in first and then provide a useful error message to the user saying unable to retrieve plans / devices, please login first.
Activity
tpoliaw commentedon Apr 7, 2026
I'm pretty sure it should return valid JSON when not logged in. I'm guessing this error is from oauth2-proxy redirecting the request and then returning HTML.
The error could still be improved in the "server returned invalid json" case but I think this is more to do with deployment configuration than blueapi.
[-]BlueapiClient gives unhelpful error message when not logged in[/-][+]BlueapiClient gives unhelpful error message when invalid JSON is returned[/+]tpoliaw commentedon Apr 8, 2026
Steps to reproduce in dev environment
docker compose -f tests/system_tests/compose.yaml up -d(see docs)uv run blueapi -c tests/system_tests/config.yaml servehttp://localhost:4180, leaving the server runninguv run blueapi -c path/to/updated/config.yaml controller plans