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| 1 | +"""Tiny-model fixture: SmolLM2-135M-Instruct, cached and reused across tests. |
| 2 | + |
| 3 | +Design notes: |
| 4 | + |
| 5 | +- Sprint 06 owns the base-model registry with pinned revisions. Until that |
| 6 | + lands, we accept `main` here and print a warning on first use. The CI |
| 7 | + cache key includes the stored revision, so cache hits are stable. |
| 8 | +- `snapshot_download` into the caller's `HF_HOME` (set by CI to a cached |
| 9 | + location). Local runs default to `~/.cache/huggingface`. |
| 10 | +- This module imports `huggingface_hub` lazily so test collection stays |
| 11 | + fast for paths that don't need the tiny model. |
| 12 | +""" |
| 13 | + |
| 14 | +from __future__ import annotations |
| 15 | + |
| 16 | +import logging |
| 17 | +import os |
| 18 | +from collections.abc import Iterator |
| 19 | +from pathlib import Path |
| 20 | +from typing import Final |
| 21 | + |
| 22 | +import pytest |
| 23 | + |
| 24 | +_LOG: Final = logging.getLogger(__name__) |
| 25 | + |
| 26 | +TINY_MODEL_HF_ID: Final = "HuggingFaceTB/SmolLM2-135M-Instruct" |
| 27 | + |
| 28 | +# TODO(sprint-06): pin to a 40-char commit SHA via the base-model registry. |
| 29 | +TINY_MODEL_REVISION: Final = os.environ.get("DLM_TINY_MODEL_REVISION", "main") |
| 30 | + |
| 31 | + |
| 32 | +def tiny_model_path() -> Path: |
| 33 | + """Download (if needed) the tiny model; return the cached directory path. |
| 34 | + |
| 35 | + Raises on network failure in offline mode; callers must mark their tests |
| 36 | + with `online` + `slow`. |
| 37 | + """ |
| 38 | + # Lazy import so fast-path tests never pull huggingface_hub. |
| 39 | + from huggingface_hub import snapshot_download |
| 40 | + |
| 41 | + if TINY_MODEL_REVISION == "main": |
| 42 | + _LOG.warning( |
| 43 | + "TINY_MODEL_REVISION unpinned (using 'main'). Sprint 06 will pin.", |
| 44 | + ) |
| 45 | + |
| 46 | + cache_dir = snapshot_download( |
| 47 | + repo_id=TINY_MODEL_HF_ID, |
| 48 | + revision=TINY_MODEL_REVISION, |
| 49 | + local_files_only=_offline_mode(), |
| 50 | + ) |
| 51 | + return Path(cache_dir) |
| 52 | + |
| 53 | + |
| 54 | +def _offline_mode() -> bool: |
| 55 | + return os.environ.get("HF_HUB_OFFLINE", "0") == "1" |
| 56 | + |
| 57 | + |
| 58 | +# --- pytest fixture wrapper --------------------------------------------------- |
| 59 | + |
| 60 | + |
| 61 | +@pytest.fixture(scope="session") |
| 62 | +def tiny_model_dir() -> Iterator[Path]: |
| 63 | + """Session-scoped fixture — download happens once per test session. |
| 64 | + |
| 65 | + Tests that use it must carry `@pytest.mark.online` and usually |
| 66 | + `@pytest.mark.slow`. |
| 67 | + """ |
| 68 | + # Clear the autouse offline env for this fixture's scope so downloads work |
| 69 | + # in tests that opted in (the `online` marker is the gate). |
| 70 | + original = { |
| 71 | + "HF_HUB_OFFLINE": os.environ.pop("HF_HUB_OFFLINE", None), |
| 72 | + "TRANSFORMERS_OFFLINE": os.environ.pop("TRANSFORMERS_OFFLINE", None), |
| 73 | + "HF_DATASETS_OFFLINE": os.environ.pop("HF_DATASETS_OFFLINE", None), |
| 74 | + } |
| 75 | + try: |
| 76 | + yield tiny_model_path() |
| 77 | + finally: |
| 78 | + for k, v in original.items(): |
| 79 | + if v is not None: |
| 80 | + os.environ[k] = v |
| 81 | + else: |
| 82 | + os.environ.pop(k, None) |
