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| """YAML-to-Pydantic config loader. | |
| Why this exists separately from ``schema.py``: | |
| * Schema is *what* a valid config looks like; loader is *how* you build one. | |
| Splitting them lets tests build an ``AppConfig`` programmatically without | |
| touching disk, and lets the loader gain features (env-file resolution, | |
| multi-file merging) without changing the schema. | |
| """ | |
| from __future__ import annotations | |
| from pathlib import Path | |
| from typing import Any | |
| import yaml | |
| from pydantic_settings import EnvSettingsSource | |
| from captioning.config.schema import AppConfig | |
| def load_config(path: str | Path) -> AppConfig: | |
| """Load a YAML file into an ``AppConfig``, apply env overrides, and validate it. | |
| Precedence, highest first: ``CAPTIONING__*`` environment variables, the | |
| YAML file, the schema defaults. An override replaces only the field it | |
| names (``CAPTIONING__SERVE__BEAM_WIDTH=4`` keeps the rest of ``serve``); | |
| a list value, such as ``CAPTIONING__SERVE__CORS_ALLOWED_ORIGINS``, | |
| replaces the YAML list whole. | |
| Args: | |
| path: Path to a YAML file with the structure:: | |
| data: {...} | |
| model: {...} | |
| train: {...} | |
| serve: {...} | |
| Returns: | |
| A fully validated, immutable ``AppConfig`` instance. | |
| Raises: | |
| FileNotFoundError: If the YAML path does not exist. | |
| pydantic.ValidationError: If any field fails validation. | |
| pydantic_settings.sources.SettingsError: If an env value for a list or | |
| section isn't valid JSON. | |
| """ | |
| path = Path(path) | |
| if not path.is_file(): | |
| raise FileNotFoundError(f"Config file not found: {path}") | |
| with path.open(encoding="utf-8") as f: | |
| raw: dict[str, Any] = yaml.safe_load(f) or {} | |
| # pydantic-settings ranks constructor arguments above the environment, so | |
| # ``AppConfig(**raw)`` alone would let the YAML win. Merge the env values | |
| # over it first, parsed by the same source ``AppConfig`` uses. | |
| env = EnvSettingsSource(AppConfig)() | |
| return AppConfig(**_merge(raw, env)) | |
| def _merge(base: dict[str, Any], override: dict[str, Any]) -> dict[str, Any]: | |
| """Return ``base`` updated by ``override``, recursing into sections both set. | |
| Any other value, lists included, is replaced whole, as pydantic-settings | |
| merges its own sources. | |
| """ | |
| merged = dict(base) | |
| for key, value in override.items(): | |
| if isinstance(value, dict) and isinstance(merged.get(key), dict): | |
| merged[key] = _merge(merged[key], value) | |
| else: | |
| merged[key] = value | |
| return merged | |