change default cache directory to follow XDG convention and respect user env overrides

Author: yaugenst-flex

tidy3d/config/sections.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import os
 import ssl
 from os import PathLike
 from pathlib import Path
@@ -385,6 +386,21 @@ def apply_web(config: WebConfig) -> None:
     manager.apply_web_env(dict(config.env_vars))
 
 
+def _default_cache_directory() -> Path:
+    """Determine the default on-disk cache directory respecting platform conventions."""
+
+    base_override = os.getenv("TIDY3D_BASE_DIR")
+    if base_override:
+        base = Path(base_override).expanduser().resolve() / ".cache"
+    else:
+        xdg_cache = os.getenv("XDG_CACHE_HOME")
+        if xdg_cache:
+            base = Path(xdg_cache).expanduser().resolve()
+        else:
+            base = Path.home() / ".cache"
+    return (base / "tidy3d" / "simulations").resolve()
+
+
 @register_section("local_cache")
 class LocalCacheConfig(ConfigSection):
     """Settings controlling the optional local simulation cache."""
@@ -397,7 +413,7 @@ class LocalCacheConfig(ConfigSection):
     )
 
     directory: DirectoryPath = Field(
-        Path.home() / ".tidy3d" / "cache",
+        default_factory=_default_cache_directory,
         title="Cache directory",
         description="Directory where cached artifacts are stored.",
         json_schema_extra={"persist": True},

tidy3d/web/cache.py

@@ -22,15 +22,9 @@
 from tidy3d.web.core.constants import TaskId
 from tidy3d.web.core.http_util import get_version as _get_protocol_version
 
-DEFAULT_CACHE_RELATIVE_DIR = Path(".tidy3d") / "cache" / "simulations"
 CACHE_ARTIFACT_NAME = "simulation_data.hdf5"
 CACHE_METADATA_NAME = "metadata.json"
 
-ENV_ENABLE = "TIDY3D_CACHE_ENABLED"
-ENV_DIRECTORY = "TIDY3D_CACHE_DIR"
-ENV_MAX_SIZE = "TIDY3D_CACHE_MAX_SIZE_GB"
-ENV_MAX_ENTRIES = "TIDY3D_CACHE_MAX_ENTRIES"
-
 TMP_PREFIX = "tidy3d-cache-"
 TMP_BATCH_PREFIX = "tmp_batch"