test: share numba kernel cache across manager tests instead of per-test recompile

[wlgys8]

问题

motrix_env_core/tests/test_numba_manager.py 的 autouse fixture _isolated_numba_cache 在每个测试前清空进程内 _KERNEL_CACHE / _TERM_CACHE，并把 NUMBA_CACHE_DIR 指向每个测试独立的空 tmp 目录。框架自带的同 plan 去重被完全绕过，28 个测试每个都全额重编译 Numba kernel（每个 ~1.2s，总计 ~26–31s）。

修改

把原 autouse fixture 拆成两层：

• _shared_numba_cache_dir（autouse）：为整个测试文件设置一个共享的 hermetic 磁盘缓存目录（tmp_path_factory，不落用户缓存），但不清空进程内缓存——同一 plan 全文件只编译一次；
• _isolated_numba_cache（普通 fixture）：保留原有的冷缓存隔离语义，仅由真正验证缓存隔离行为的测试显式引用：
  • test_materialize_source_is_safe_for_concurrent_same_plan_writers
  • test_build_rematerializes_source_after_cache_invalidation
  • test_specialization_cache_failure_rebuilds_callable_dispatchers_before_retry
  • test_reset_descriptor_is_part_of_numba_kernel_cache_key

语义上也更准确：绝大多数测试验证的是 env 行为契约，不需要冷缓存隔离。

效果

	修复前	修复后
test_numba_manager.py	28 passed in ~26–31s	28 passed in ~11.5s
motrix_env_core/tests 全量	—	127 passed，无回归

测试数量与覆盖不变。

Fixes #32

[Copilot]

🟡 Changes recommended

The new “shared cache dir” fixture is currently function-scoped (creating a new cache dir per test) and the isolated-cache fixture clears global caches without restoring them, making the behavior order-dependent and not fully matching the stated intent.

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Pull request overview

This PR optimizes motrix_env_core’s Numba manager test runtime by stopping per-test forced cold-cache recompilation and instead allowing kernel compilation reuse across tests, while keeping explicit “cold cache” isolation for the few tests that validate cache behavior.

Changes:

• Introduces an autouse fixture intended to provide a hermetic NUMBA_CACHE_DIR for the file without clearing in-process caches.
• Converts _isolated_numba_cache from an autouse fixture to an opt-in fixture and wires it into the specific cache-isolation tests.

File summaries

File	Description
motrix_env_core/tests/test_numba_manager.py	Refactors pytest fixtures to reduce redundant Numba kernel recompilation and makes cache-isolation behavior opt-in for specific tests.

Review details

Suppressed comments (1)

motrix_env_core/tests/test_numba_manager.py:301

• _isolated_numba_cache clears the global in-process caches but never restores them, so tests that run after an isolated-cache test will see a cold cache again (order-dependent behavior and avoidable recompilation). Consider snapshotting and restoring the caches in a yield fixture so isolation is limited to the tests that request it.

@pytest.fixture
def _isolated_numba_cache(tmp_path, monkeypatch):
    monkeypatch.setenv("NUMBA_CACHE_DIR", str(tmp_path / "numba-cache"))
    compiler_module._KERNEL_CACHE.clear()
    compiler_module._TERM_CACHE.clear()

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Lite

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[Copilot]

🔵 Needs a closer look

The new “shared cache dir” fixture currently creates a fresh tmp cache directory per test, contradicting the intended single shared on-disk cache directory behavior.

Review details

Suppressed comments (1)

motrix_env_core/tests/test_numba_manager.py:292

• _shared_numba_cache_dir is function-scoped and calls tmp_path_factory.mktemp(...) each test, so it creates a new cache directory per test rather than sharing a single on-disk cache directory across the whole file as described. This defeats cross-test disk-cache reuse and causes repeated source materialization in different directories even when the in-process cache hits.

# Share a single on-disk cache directory across the whole test file (hermetic,
# never touches the user cache), but do not clear the in-process kernel caches:
# each distinct plan is compiled once instead of per-test full recompilation
# caused by cache-clearing autouse fixtures (issue #32).
@pytest.fixture(autouse=True)
def _shared_numba_cache_dir(tmp_path_factory, monkeypatch):
    monkeypatch.setenv("NUMBA_CACHE_DIR", str(tmp_path_factory.mktemp("numba-cache")))

• Files reviewed: 2/2 changed files
• Comments generated: 0 new
• Review effort level: Lite

[Copilot]

🟢 Approval recommended

The change is confined to test fixtures/documentation and preserves isolation coverage by making cold-cache behavior explicit only where required.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0 new
• Review effort level: Lite