🐛 Fix PermissionError when run by supervisor with cache is true

fastapi_cdn_host/client.py

@@ -2,7 +2,9 @@
 import inspect
 import logging
 import math
+import os
 import re
+import sys
 from dataclasses import dataclass
 from enum import Enum
 from pathlib import Path
@@ -236,6 +238,7 @@ class CdnHostBuilder:
     swagger_ui_full_version = "5.17.14"
     swagger_files = {"css": "swagger-ui.css", "js": "swagger-ui-bundle.js"}
     redoc_file = "redoc.standalone.js"
+    default_cache_file = "~/.cache/fastapi-cdn-host/urls.txt"
 
     def __init__(
         self, app=None, docs_cdn_host=None, favicon_url=None, cache=None
@@ -281,14 +284,26 @@ def run(self) -> AssetUrl:
             return urls
         return self._cache_wrap(self.run_async)(self.sniff_the_fastest, favicon)
 
+    def get_cache_file(self) -> Tuple[bool, Path]:
+        file = Path(os.path.expanduser(self.default_cache_file))
+        try:
+            exists = file.exists()
+        except PermissionError:
+            tmp_dir = Path("/tmp")  # nosec:B108
+            if sys.platform == "win32":
+                tmp_dir = Path(os.getenv("temp", "."))  # NOQA:SIM112
+            file = tmp_dir / self.default_cache_file.replace("~/", "")
+            exists = file.exists()
+        return exists, file
+
     def _cache_wrap(self, func: Callable) -> Callable[..., AssetUrl]:
         if not self._cache:
             return func
 
         @functools.wraps(func)
         def wrapper(*args, **kw):
-            file = Path.home() / ".cache" / "fastapi-cdn-host" / "urls.txt"
-            if file.exists():
+            already_cached, file = self.get_cache_file()
+            if already_cached:
                 lines = file.read_text("utf8").splitlines()
                 if len(lines) == 3:
                     css = js = redoc = ""

tests/cache_is_true/test_cache_true.py

@@ -1,6 +1,8 @@
 # mypy: no-disallow-untyped-decorators
 import importlib
+import os
 import re
+import sys
 from pathlib import Path
 
 import main
@@ -73,3 +75,21 @@ async def test_docs(client: AsyncClient):  # nosec
         urls = AssetUrl(css=lines[0], js=lines[1], redoc=lines[2])
     importlib.reload(main)
     await _run_test(cache_file, urls, client)
+
+
+def test_cache_file(mocker, tmp_path):
+    file = tmp_path / "foo" / "a.txt"
+    file.parent.mkdir()
+    file.touch()
+    assert os.path.exists(str(file))
+    file.parent.chmod(0)
+    with pytest.raises(PermissionError):
+        file.exists()
+    mocker.patch("os.path.expanduser", return_value=str(file))
+    _, cache_file = CdnHostBuilder().get_cache_file()
+    if sys.platform == "win32":
+        temp_directory_env_name = "temp"
+        temp_dir = Path(os.getenv(temp_directory_env_name, "."))
+        assert cache_file == temp_dir / ".cache/fastapi-cdn-host/urls.txt"
+    else:
+        assert cache_file.as_posix() == "/tmp/.cache/fastapi-cdn-host/urls.txt"