[coverage] Conformance findings: SESSION-017 #1668

Summary

Surfaced by the multi-language coverage fan-out while conformance-testing these SPEC-IDs against databricks/databricks-jdbc. Each finding is committed as an expected-failure (xfail) test in the coverage PR — the test asserts the CORRECT (post-fix) behavior and stays red until THIS driver (databricks/databricks-jdbc) is fixed, then flips green as a tripwire.

Findings

• SESSION-017 [sea]: SEA backend (usethriftclient=0) connect+query eagerly loads the Apache Thrift protocol stack (org.apache.thrift.TSerializable via the generated TFetchResultsResp), leaking the thrift top-level namespace on a path that never speaks Thrift on the wire
  • failing test: testNonThriftBackendDoesNotLoadThriftStack (see the coverage PR diff under tests/)
• SESSION-017: SEA backend (usethriftclient=0) connect+query eagerly loads the Apache Thrift protocol stack (org.apache.thrift.TSerializable via the generated TFetchResultsResp), leaking the thrift top-level namespace on a path that never speaks Thrift on the wire — breaks builds that vendor their own Apache Thrift

Reproduce & Expected

SESSION-017 — Validates that selecting the SEA/REST backend never loads the driver's Apache Thrift protocol stack, while the Thrift backend still does.

Reproduce:

SELECT 1 AS test_value

Expected (per the shared spec):

• completes without an exception
• result has exactly 1 row(s)
• full assertion contract:

result:
- no_exception: true
  description: Every probe completes without error on every backend the driver speaks
- label: connect_and_query
  row_count: 1
  description: 'The query still returns its single row -- deferring the Thrift references
    must

    not break execution on either backend.

    '
- label: backend_import
  thrift_stack_loaded: false
  description: 'Loading the public entry point and the non-Thrift backend components
    loads no

    Thrift protocol module. Protocol-agnostic: these components are the same

    artifacts regardless of which backend the run selects.

    '
- label: thrift_backend_import
  thrift_stack_loaded: true
  description: 'The Thrift backend still loads the Thrift protocol stack -- guards
    against a

    "fix" that hides Thrift so far that the Thrift path itself breaks.

    '
- label: legacy_symbols
  symbols_resolve: true
  description: 'The historically public protocol-typed symbols still resolve. Resolution
    may

    load the Thrift stack; that is permitted and deliberately NOT asserted.

    '
protocol:
  sea:
  - label: connect_and_query
    thrift_stack_loaded: false
    description: 'A SEA connect + query loads zero Thrift protocol modules -- the
      behavior

      that unblocks callers vendoring their own Apache Thrift.

      '
  thrift:
  - label: connect_and_query
    thrift_stack_loaded: true
    description: 'A Thrift connect + query legitimately loads the Thrift stack; asserting
      the

      non-loaded invariant here would be wrong.

      '

Context

• The behavior was first fixed in a DIFFERENT driver — reference PR: Lazy-load Apache Thrift so the SEA/kernel paths never import it databricks-sql-python#907 — which seeded the shared language-neutral spec. This issue tracks the same conformance gap in databricks/databricks-jdbc; the reference PR is for cross-referencing the intended behavior, NOT a change to this repo.
• Coverage PR carrying the reproducing xfail test(s): https://github.com/databricks/databricks-driver-test/pull/1432