feat(gcs): implement delete for GCS object store

[daiping8]

Summary

• Implements delete method for the GCS object store backend (GCSSource)
• Fixes write_parquet(write_mode='overwrite') on GCS paths (closes write_parquet(write_mode='overwrite') on GCS fails with Method not implemented: Deletes is not yet supported! #6928)

Changes

• Adds UnableToDeleteFile error variant to the GCS error enum
• Implements delete on GCSClientWrapper using google_cloud_storage's delete_object API
• Handles 404/410 responses as success (idempotent delete per ObjectSource trait contract)
• Overrides delete in ObjectSource impl for GCSSource

Test plan

• Verify write_parquet(write_mode="overwrite") succeeds on a gs:// path
• Verify delete is idempotent (overwriting a non-existent path does not fail)
• make build passes
• DAFT_RUNNER=native make test EXTRA_ARGS="-v tests/io/" passes

[greptile-apps]

Greptile Summary

This PR implements the delete method for the GCS object store backend, fixing write_parquet(write_mode='overwrite') on gs:// paths. The implementation correctly handles idempotent deletes by treating both GError::Response and GError::HttpClient 404/410 responses as success, and also refactors client-config construction to support a no-anonymous-fallback code path used in new smoke tests.

• Adds UnableToDeleteFile error variant, is_delete_idempotent_error helper, and GCSClientWrapper::delete / GCSSource::delete implementations with proper semaphore and IO-stats wiring.
• Refactors get_client into get_client_config + client_from_config to allow a test-only get_client_without_anonymous_fallback path.
• Adds Rust unit/smoke tests and a new Python integration test for the parquet-overwrite round-trip on GCS.

Confidence Score: 5/5

The change is narrowly scoped to adding a new delete operation on GCS; existing read/list paths are untouched and the refactored client-construction logic preserves the same behavior for callers of get_client.

The idempotency guards correctly cover both the API-level (GError::Response) and transport-level (GError::HttpClient) 404/410 cases, the semaphore and IO-stats wiring match the pattern used by other methods, and the client-config refactor is straightforward. The only finding is a cosmetic dead-code pattern (is_success always true).

No files require special attention.

Important Files Changed

Filename	Overview
src/daft-io/src/google_cloud.rs	Adds delete to GCSClientWrapper and GCSSource with correct idempotent 404/410 handling (both GError::Response and GError::HttpClient); refactors client-config construction; adds Rust unit and smoke tests. One minor: the is_success boolean is always true, leaving the if is_success guard as dead code.
tests/integration/io/parquet/test_writes_gcs.py	New integration test for GCS parquet overwrite; guarded by --credentials flag and GCS_WRITE_TEST_BUCKET env var, with gcsfs-based cleanup in fixture teardown. Looks correct.

Sequence Diagram

sequenceDiagram
    participant Caller
    participant GCSSource
    participant GCSClientWrapper
    participant GCSClient as google_cloud_storage Client

    Caller->>GCSSource: delete(uri, io_stats)
    GCSSource->>GCSClientWrapper: delete(uri, io_stats)
    GCSClientWrapper->>GCSClientWrapper: parse_raw_uri(uri)
    alt key is empty
        GCSClientWrapper-->>Caller: Err(NotAFile)
    else key is non-empty
        GCSClientWrapper->>GCSClientWrapper: acquire semaphore permit
        GCSClientWrapper->>GCSClient: delete_object(bucket, key)
        alt Ok(())
            GCSClient-->>GCSClientWrapper: Ok(())
            GCSClientWrapper->>GCSClientWrapper: mark_delete_requests(1)
            GCSClientWrapper-->>Caller: Ok(())
        else Err — 404 or 410
            GCSClient-->>GCSClientWrapper: Err(GError::Response 404/410 OR HttpClient 404/410)
            GCSClientWrapper->>GCSClientWrapper: is_delete_idempotent_error → true
            GCSClientWrapper->>GCSClientWrapper: mark_delete_requests(1)
            GCSClientWrapper-->>Caller: Ok(())
        else Err — other error
            GCSClient-->>GCSClientWrapper: Err(other)
            GCSClientWrapper->>GCSClientWrapper: is_delete_idempotent_error → false
            GCSClientWrapper-->>Caller: Err(UnableToDeleteFile → super::Error)
        end
    end

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_{Reviews (2): Last reviewed commit: "test(gcs): add delete and overwrite regr..." | Re-trigger Greptile}

[rchowell]

@daiping8 is this ready for review or are you still working on it?

[daiping8]

@daiping8 is this ready for review or are you still working on it?

Sorry for the late reply. I've added a commit with test code and have tested the PR as thoroughly as possible. The PR now includes two commits: one for the implementation and one for the tests. Please review, thank you.