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IndexError when printing dashboard response containing empty group_by list #3656

nainakira · 2026-06-08T06:55:36Z

**Describe the bug** Calling `print(response)` on a dashboard response raises `IndexError: list index out of range` when the dashboard contains a `query_value` widget with a logs query that has `"group_by": []` (empty list). Labels: `kind/bug`, `severity/major` **To Reproduce** 1. Create a dashboard with a `query_value` widget using a logs query with `group_by` set to an empty list. 2. Call `get_dashboard()` using the Python API client. 3. Call `print(response)` on the returned object. 4. See `IndexError: list index out of range`. Minimal reproduction: ```python from datadog_api_client import Configuration, ApiClient from datadog_api_client.v1.api.dashboards_api import DashboardsApi configuration = Configuration() with ApiClient(configuration) as api_client: api = DashboardsApi(api_client) response = api.get_dashboard(dashboard_id=" ") print(response) # raises IndexError ``` **Expected behavior** The response should be printed (or serialized via `to_dict()`) without raising any exception. **Screenshots** ``` Traceback (most recent call last): File "main.py", line 8, in print(response) File ".venv/lib/python3.14/site-packages/datadog_api_client/model_utils.py", line 194, in __repr__ return self.to_str() File ".venv/lib/python3.14/site-packages/datadog_api_client/model_utils.py", line 422, in to_str return pprint.pformat(self.to_dict()) File ".venv/lib/python3.14/site-packages/datadog_api_client/model_utils.py", line 418, in to_dict return model_to_dict(self, serialize=False) File ".venv/lib/python3.14/site-packages/datadog_api_client/model_utils.py", line 1502, in model_to_dict model = model.get_oneof_instance() File ".venv/lib/python3.14/site-packages/datadog_api_client/model_utils.py", line 581, in get_oneof_instance return self._composed_instances[0] IndexError: list index out of range ``` **Root cause** `group_by` is typed as `FormulaAndFunctionEventQueryGroupByConfig`, a `ModelComposed` class with a `oneOf` of two variants: a list of group-by objects and a fields object. When the API returns `"group_by": []`, the `oneOf` matcher cannot determine which variant the empty list belongs to, so `_composed_instances` is left empty. `model_to_dict()` in `model_utils.py` enters its traversal loop based on `_composed_schemas` being non-empty, without checking whether `_composed_instances` is populated, and then crashes at `get_oneof_instance()` which unconditionally accesses `self._composed_instances[0]`. **Workaround** Set `configuration.preload_content = False` to skip deserialization and parse the raw JSON manually: ```python import json from datadog_api_client import Configuration, ApiClient from datadog_api_client.v1.api.dashboards_api import DashboardsApi configuration = Configuration() configuration.preload_content = False with ApiClient(configuration) as api_client: api = DashboardsApi(api_client) response = api.get_dashboard(dashboard_id=" ") data = json.loads(response.data) print(json.dumps(data, indent=2)) ``` **Environment and Versions (please complete the following information):** - `datadog-api-client` version: 2.55.0 (latest) - Python version: 3.14 - OS: macOS **Additional context** The fix requires two changes in `.generator/src/generator/templates/model_utils.j2` (the template that generates `src/datadog_api_client/model_utils.py`): 1. Guard the loop in `model_to_dict()` to only enter when `_composed_instances` is also non-empty: ```python while model._composed_schemas and model._composed_instances: ``` 2. Make `get_oneof_instance()` fall back to `self` instead of crashing when `_composed_instances` is empty: ```python def get_oneof_instance(self): if not self._composed_instances: return self return self._composed_instances[0] ```

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IndexError when printing dashboard response containing empty group_by list #3656

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