feat: centralized environment handling, ensures ZEN_MCP_FORCE_ENV_OVERRIDE is honored correctly

fix: updated tests to override env variables they need instead of relying on the current values from .env

utils/env.py

@@ -0,0 +1,88 @@
+"""Centralized environment variable access for Zen MCP Server."""
+
+from __future__ import annotations
+
+import os
+from collections.abc import Mapping
+from pathlib import Path
+
+try:
+    from dotenv import dotenv_values, load_dotenv
+except ImportError:  # pragma: no cover - optional dependency
+    dotenv_values = None  # type: ignore[assignment]
+    load_dotenv = None  # type: ignore[assignment]
+
+_PROJECT_ROOT = Path(__file__).resolve().parent.parent
+_ENV_PATH = _PROJECT_ROOT / ".env"
+
+_DOTENV_VALUES: dict[str, str | None] = {}
+_FORCE_ENV_OVERRIDE = False
+
+
+def _read_dotenv_values() -> dict[str, str | None]:
+    if dotenv_values is not None and _ENV_PATH.exists():
+        loaded = dotenv_values(_ENV_PATH)
+        return dict(loaded)
+    return {}
+
+
+def _compute_force_override(values: Mapping[str, str | None]) -> bool:
+    raw = (values.get("ZEN_MCP_FORCE_ENV_OVERRIDE") or "false").strip().lower()
+    return raw == "true"
+
+
+def reload_env(dotenv_mapping: Mapping[str, str | None] | None = None) -> None:
+    """Reload .env values and recompute override semantics.
+
+    Args:
+        dotenv_mapping: Optional mapping used instead of reading the .env file.
+            Intended for tests; when provided, load_dotenv is not invoked.
+    """
+
+    global _DOTENV_VALUES, _FORCE_ENV_OVERRIDE
+
+    if dotenv_mapping is not None:
+        _DOTENV_VALUES = dict(dotenv_mapping)
+        _FORCE_ENV_OVERRIDE = _compute_force_override(_DOTENV_VALUES)
+        return
+
+    _DOTENV_VALUES = _read_dotenv_values()
+    _FORCE_ENV_OVERRIDE = _compute_force_override(_DOTENV_VALUES)
+
+    if load_dotenv is not None and _ENV_PATH.exists():
+        load_dotenv(dotenv_path=_ENV_PATH, override=_FORCE_ENV_OVERRIDE)
+
+
+reload_env()
+
+
+def env_override_enabled() -> bool:
+    """Return True when ZEN_MCP_FORCE_ENV_OVERRIDE is enabled via the .env file."""
+
+    return _FORCE_ENV_OVERRIDE
+
+
+def get_env(key: str, default: str | None = None) -> str | None:
+    """Retrieve environment variables respecting ZEN_MCP_FORCE_ENV_OVERRIDE."""
+
+    if env_override_enabled():
+        if key in _DOTENV_VALUES:
+            value = _DOTENV_VALUES[key]
+            return value if value is not None else default
+        return default
+
+    return os.getenv(key, default)
+
+
+def get_env_bool(key: str, default: bool = False) -> bool:
+    """Boolean helper that respects override semantics."""
+
+    raw_default = "true" if default else "false"
+    raw_value = get_env(key, raw_default)
+    return (raw_value or raw_default).strip().lower() == "true"
+
+
+def get_all_env() -> dict[str, str | None]:
+    """Expose the loaded .env mapping for diagnostics/logging."""
+
+    return dict(_DOTENV_VALUES)