fix: handle malformed api_constraints without crashing endpoint (#273)

[Gokul-social]

Summary

Hardens the /tasktype/{task_type_id} endpoint against inconsistent api_constraints data. Fixes #273.

The Problem

The existing implementation was fragile, relying on strict json.loads() and direct key access. This led to unnecessary 500 errors when encountering:

• Malformed JSON strings or unexpected dict types in the persistence layer.
• Missing data_type keys, triggering unhandled KeyErrors.
• Type mismatches that caused the parser to bail instead of degrading gracefully.

The Solution

I've introduced a defensive parse_api_constraints helper to act as a buffer between the DB and the response.

• Type Agnostic Parsing: Gracefully handles both JSON strings and pre-parsed dictionaries.
• Non-Breaking Validation: Switched to .get() with strict type-checking for data_type. If a value is invalid, it is omitted from the output rather than crashing the request.
• Observability: Added structured logging (WARNING for structural failures, DEBUG for missing data) prefixed with api_constraints: to help us audit bad data in production.

Testing

Comprehensive unit tests added to cover:

• Valid/Malformed JSON and raw dict inputs.
• Boundary cases: Empty values, nulls, and unsupported schema types.
• Verification that response structure remains backward compatible.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 02939bc3-0108-4e88-af35-3c81d87801ee

📥 Commits

Reviewing files that changed from the base of the PR and between ea00485 and 4fca9fb.

📒 Files selected for processing (2)

• src/routers/openml/tasktype.py
• tests/routers/openml/test_parse_api_constraints.py

🚧 Files skipped from review as they are similar to previous changes (1)

• tests/routers/openml/test_parse_api_constraints.py

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Walkthrough

Adds module-level logging and a new helper parse_api_constraints(api_constraints: str | Mapping[str, object] | None, *, task_type_id: int, input_name: str) -> str | None in src/routers/openml/tasktype.py that defensively handles None, dict, and JSON-string inputs and returns a non-empty data_type string or None. Updates get_task_type so input[].data_type is included only when the helper returns a valid data_type; the function docstring documents this field as optional. Adds tests/routers/openml/test_parse_api_constraints.py covering parsing edge cases and expected logging.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: handling malformed api_constraints to prevent endpoint crashes, with a direct reference to the issue.
Description check	✅ Passed	The description comprehensively explains the problem, solution, and testing approach, directly relating to the changeset's defensive parsing and logging improvements.
Linked Issues check	✅ Passed	The PR fully addresses all coding requirements from issue #273: defensive parsing of both JSON strings and dicts, graceful error handling, conditional data_type inclusion, and structured logging with proper observability.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing the api_constraints parsing issue: new parse_api_constraints helper, updated get_task_type behavior, comprehensive unit tests, and logging additions.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[sourcery-ai]

Hey - I've left some high level feedback:

• In parse_api_constraints, you currently only accept plain dict instances; if upstream ever passes a Mapping (e.g. dict-like) object it will be treated as unsupported, so consider loosening the type check to collections.abc.Mapping to make the helper more robust to different ORM or serialization layers.
• The test_valid_constraint_no_warning assertion len(caplog.records) == 0 can be brittle if any other logger emits during the test run; it would be safer to assert that there are no records from the specific logger or containing the api_constraints: prefix instead of enforcing an absolutely empty log.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In `parse_api_constraints`, you currently only accept plain `dict` instances; if upstream ever passes a `Mapping` (e.g. `dict`-like) object it will be treated as unsupported, so consider loosening the type check to `collections.abc.Mapping` to make the helper more robust to different ORM or serialization layers.
- The `test_valid_constraint_no_warning` assertion `len(caplog.records) == 0` can be brittle if any other logger emits during the test run; it would be safer to assert that there are no records from the specific logger or containing the `api_constraints:` prefix instead of enforcing an absolutely empty log.

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[Copilot]

Pull request overview

Hardens the /tasktype/{task_type_id} endpoint so malformed or inconsistent api_constraints data no longer causes 500s, aligning behavior with issue #273.

Changes:

• Added parse_api_constraints helper to defensively parse api_constraints and safely extract data_type.
• Updated task type response construction to include input[].data_type only when valid.
• Added unit tests covering valid/malformed inputs and logging behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/routers/openml/tasktype.py	Introduces defensive parsing + logging and uses it when building the /tasktype/{id} response.
tests/routers/openml/test_parse_api_constraints.py	Adds unit tests for parsing outcomes and emitted log levels/messages.

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