Add datasource datapoint lookup by path

[sirajhoshan]

Summary

• add Datasource.get_datapoint(path) for direct datapoint lookup
• reuse the existing path filtering mechanism
• fetch at most one matching datapoint
• preserve KeyError when the requested path does not exist
• add tests for both found and missing paths

Tests

• PYTHONPATH="$PWD" python -m pytest tests/data_engine/test_datasource.py -q
• PYTHONPATH="$PWD" python -m pytest tests/data_engine/test_querying.py tests/data_engine/test_queryresult.py tests/data_engine/test_datapoint.py -q
• python -m black --check dagshub/data_engine/model/datasource.py tests/data_engine/test_datasource.py
• git diff --check

Fixes #365

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 733227f and ad54024.

📒 Files selected for processing (2)

• dagshub/data_engine/model/datasource.py
• tests/data_engine/test_datasource.py

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📜 Recent review details

🔇 Additional comments (2)

dagshub/data_engine/model/datasource.py (1)

340-343: LGTM!

tests/data_engine/test_datasource.py (1)

285-313: LGTM!

Also applies to: 316-328

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📝 Walkthrough

Walkthrough

Datasource now provides get_datapoint(path) to query one datapoint by path. Tests cover the matching result and the KeyError raised when no datapoint exists.

Changes

Datapoint path lookup

Layer / File(s)	Summary
Path lookup API and validation dagshub/data_engine/model/datasource.py, tests/data_engine/test_datasource.py	Datasource.get_datapoint filters by path, limits the query to one result, returns the matching Datapoint, and raises KeyError when no result exists. Tests verify both cases and inspect the query filter.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to ad540

This PR adds a localized datapoint lookup method with missing-path handling and focused tests; no actionable merge-blocking risk remains after normal checks and review.

Poem

I hop through paths where datapoints hide,
One query brings the right one inside.
If none is found, a key error calls,
The rabbit approves these tidy halls. 🐇

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: adding datapoint lookup by path to Datasource.
Description check	✅ Passed	The description directly explains the new lookup method, its behavior, tests, and validation commands.
Linked Issues check	✅ Passed	The implementation satisfies issue #365 by adding direct datapoint retrieval through path filtering and preserving KeyError for missing paths.
Out of Scope Changes check	✅ Passed	The changes are limited to the requested Datasource method and focused tests for successful and missing path lookups.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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Warning

⚠️ This pull request shows signs of AI-generated slop (redundant_comments). It has been flagged by CodeRabbit slop detection and should be reviewed carefully.