learningcircuit--local-deep-research/tests/embeddings/splitters/test_lazy_import_guard.py

"""Boot-lightness guard for the lazy text-splitter import.

``text_splitter_registry`` deliberately imports ``langchain_text_splitters``
(which eagerly pulls sentence-transformers / torch / spaCy / nltk, ~500 MB)
*lazily*, inside ``get_text_splitter`` — so it stays off the app-startup
import chain (scheduler / blueprints / search engines all import
``LibraryRAGService`` -> ``embeddings.splitters``). Importing it at boot
added ~17 s to CI server startup and tipped the UI-test gates over.

This test makes that contract explicit and enforced. The UI gates only
fail when boot breaks *entirely*; this fails fast and deterministically the
moment someone re-adds an eager heavy import to the startup chain — which is
the textbook mitigation for lazy imports ("cover the lazy path with a
test"). It must run in a fresh interpreter: inside the pytest process
``langchain_text_splitters`` is already imported by sibling tests, so the
assertion would be meaningless.
"""

import subprocess
import sys
import textwrap

# allow: no-sut-import — the modules under test are imported inside the
# subprocess driver below; the boot-lightness property only holds in a fresh
# interpreter (sibling tests warm these modules in the pytest process).

# Import the two modules that sit on the app-startup chain and must NOT drag
# in the heavy splitter stack, then assert it stayed unimported.
_DRIVER = textwrap.dedent(
    """
    import sys

    import local_deep_research.embeddings.splitters.text_splitter_registry  # noqa: F401
    import local_deep_research.research_library.services.library_rag_service  # noqa: F401

    eager = [
        m for m in ("langchain_text_splitters", "sentence_transformers")
        if m in sys.modules
    ]
    if eager:
        print(f"FAIL: app-startup import chain eagerly loaded {eager}")
        sys.exit(1)
    print("OK")
    """
)


def test_startup_chain_does_not_eagerly_import_text_splitters():
    """The startup import chain must not pull in langchain_text_splitters."""
    result = subprocess.run(
        [sys.executable, "-c", _DRIVER],
        capture_output=True,
        text=True,
        timeout=120,
    )
    assert result.returncode == 0, (
        "Boot-lightness regression: a module on the app-startup chain now "
        "eagerly imports the heavy text-splitter stack. Keep the "
        "langchain_text_splitters import lazy (inside get_text_splitter).\n"
        f"stdout: {result.stdout}\nstderr: {result.stderr[-1500:]}"
    )
    assert "OK" in result.stdout