[ddehilster]

Background

Today on Windows, NLPPlus.Engine() (auto-tempdir form) silences a PermissionError during cleanup via TemporaryDirectory(prefix=..., ignore_cleanup_errors=True) — PR #24. The error came from the C++ engine holding <workfolder>/logs/cgerr.log open at process exit; Python's tempdir cleanup ran during atexit, before nanobind tore down the NLP_ENGINE instance, so Windows refused to delete a directory containing an open file.

The band-aid leaks the tempdir on disk and silences a real ordering bug.

The companion engine PR (nlp-engine#641, shipped in v3.1.55 as NLP-ENGINE-523) made NLP_ENGINE::close() idempotent so it can be called explicitly from Python without breaking the existing ~NLP_ENGINE → close() path.

What this PR does

1. Bump nlp-engine submodule to v3.1.55.

2. bindings.cpp: expose NLP_ENGINE::close() via nanobind:

   .def("close", &NLP_ENGINE::close,
        "Tear down the engine's VTRun runtime and release the open "
        "<workfolder>/logs/cgerr.log handle. Safe to call multiple "
        "times (engine v3.1.55+ NLP-ENGINE-523 made close() idempotent). ...");

3. NLPPlus/__init__.py Engine:

   • New close() method — calls self.engine.close(), then self.tmpdir.cleanup() if applicable. Idempotent via self._closed guard.
   • New __enter__ / __exit__ so users can do with NLPPlus.Engine() as e: ... and get deterministic cleanup.
   • New __del__ that best-effort calls close() (swallows exceptions because the bindings module may be torn down during interpreter shutdown).
   • AttributeError fallback in close() if someone runs new NLPPlus against an older engine binding without .close() exposed — degrades to the old behaviour.

4. ignore_cleanup_errors=True stays as defense-in-depth, not as the load-bearing fix:

   • with / explicit close() → engine closes, tempdir rmtree's cleanly. No PermissionError, no leaked tempdir.
   • del e → __del__ best-effort closes too. Usually clean.
   • Crash / os._exit / shutdown ordering preventing __del__ from running → flag catches it, stderr stays quiet, OS reclaims tempdir at process exit anyway.

Test plan

# 1. Explicit close — preferred for scripts
e = NLPPlus.Engine()
e.analyze("hello world", "parse-en-us")
e.close()                                # tempdir gone, no PermissionError

# 2. Context manager — preferred for blocks
with NLPPlus.Engine() as e:
    e.analyze("hello world", "parse-en-us")
                                          # tempdir gone at end of block

# 3. Implicit / legacy — still works, no regression
e = NLPPlus.Engine()
e.analyze("hello world", "parse-en-us")
del e                                     # __del__ closes; tempdir cleans

On Windows: verify with Process Monitor that <workfolder> is gone after close() returns, and that there's no stale PermissionError traceback on del e.

Versioning

Ready for the next NLPPlus release (would be v2.0.4) once this merges:

git tag -a v2.0.4 -m "..." && git push upstream v2.0.4

The bundled engine is now v3.1.55, so PyPI consumers get the deterministic-close path automatically.