test(io): stop test_cloud_paths from resolving S3 region over network

[wjones127]

object_store::tests::test_cloud_paths is failing on main in the Rust CI job.

The test opens s3://bucket/foo.lance with no region configured. resolve_s3_region then makes a live HEAD request to bucket.s3.amazonaws.com to read the x-amz-bucket-region header. That request is flaky in CI: when the header is absent the call fails with RegionParse { bucket: "bucket" }, panicking the .unwrap(). In the same failing run, test_block_size_used_cloud::case_1 — which hits the identical code path — passed, confirming the failure is non-deterministic network behavior, not a logic regression.

The affected tests only verify URL/path parsing, so they have no reason to reach the network. This passes a static region storage option for the S3 cases, which short-circuits resolve_s3_region before any request is made. test_block_size_used_cloud's S3 case shares the same flaw and is fixed the same way.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Improved cloud storage testing reliability by using a fixed S3 region configuration.
  • Prevented tests from requiring live region resolution when validating S3 paths and block size behavior.

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ℹ️ Recent review info

⚙️ Run configuration

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Review profile: ASSERTIVE

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Run ID: 0a1715ed-7eb3-48af-9abc-fe3c8f23518d

📥 Commits

Reviewing files that changed from the base of the PR and between 234fc2a and 33c1025.

📒 Files selected for processing (1)

• rust/lance-io/src/object_store.rs

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📝 Walkthrough

Walkthrough

S3-related tests now pass static us-east-1 storage options when constructing object stores and testing block-size behavior, while preserving existing path and scheme assertions.

Changes

S3 test configuration

Layer / File(s)	Summary
Static S3 region options rust/lance-io/src/object_store.rs	test_cloud_paths and the S3 block-size test case use storage options containing the static us-east-1 region instead of relying on live region resolution.

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

Suggested reviewers: jackye1995, xuanwo

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: avoiding S3 region resolution during tests to prevent network calls.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[codecov]

Codecov Report

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