Воркед

venv/Lib/site-packages/pip/_internal/network/cache.py

@@ -3,10 +3,11 @@
 
 import os
 from contextlib import contextmanager
-from typing import Generator, Optional
+from datetime import datetime
+from typing import BinaryIO, Generator, Optional, Union
 
-from pip._vendor.cachecontrol.cache import BaseCache
-from pip._vendor.cachecontrol.caches import FileCache
+from pip._vendor.cachecontrol.cache import SeparateBodyBaseCache
+from pip._vendor.cachecontrol.caches import SeparateBodyFileCache
 from pip._vendor.requests.models import Response
 
 from pip._internal.utils.filesystem import adjacent_tmp_file, replace
@@ -28,10 +29,22 @@ def suppressed_cache_errors() -> Generator[None, None, None]:
         pass
 
 
-class SafeFileCache(BaseCache):
+class SafeFileCache(SeparateBodyBaseCache):
     """
     A file based cache which is safe to use even when the target directory may
     not be accessible or writable.
+
+    There is a race condition when two processes try to write and/or read the
+    same entry at the same time, since each entry consists of two separate
+    files (https://github.com/psf/cachecontrol/issues/324).  We therefore have
+    additional logic that makes sure that both files to be present before
+    returning an entry; this fixes the read side of the race condition.
+
+    For the write side, we assume that the server will only ever return the
+    same data for the same URL, which ought to be the case for files pip is
+    downloading.  PyPI does not have a mechanism to swap out a wheel for
+    another wheel, for example.  If this assumption is not true, the
+    CacheControl issue will need to be fixed.
     """
 
     def __init__(self, directory: str) -> None:
@@ -43,27 +56,63 @@ class SafeFileCache(BaseCache):
         # From cachecontrol.caches.file_cache.FileCache._fn, brought into our
         # class for backwards-compatibility and to avoid using a non-public
         # method.
-        hashed = FileCache.encode(name)
+        hashed = SeparateBodyFileCache.encode(name)
         parts = list(hashed[:5]) + [hashed]
         return os.path.join(self.directory, *parts)
 
     def get(self, key: str) -> Optional[bytes]:
-        path = self._get_cache_path(key)
+        # The cache entry is only valid if both metadata and body exist.
+        metadata_path = self._get_cache_path(key)
+        body_path = metadata_path + ".body"
+        if not (os.path.exists(metadata_path) and os.path.exists(body_path)):
+            return None
         with suppressed_cache_errors():
-            with open(path, "rb") as f:
+            with open(metadata_path, "rb") as f:
                 return f.read()
 
-    def set(self, key: str, value: bytes, expires: Optional[int] = None) -> None:
-        path = self._get_cache_path(key)
+    def _write(self, path: str, data: bytes) -> None:
         with suppressed_cache_errors():
             ensure_dir(os.path.dirname(path))
 
             with adjacent_tmp_file(path) as f:
-                f.write(value)
+                f.write(data)
+                # Inherit the read/write permissions of the cache directory
+                # to enable multi-user cache use-cases.
+                mode = (
+                    os.stat(self.directory).st_mode
+                    & 0o666  # select read/write permissions of cache directory
+                    | 0o600  # set owner read/write permissions
+                )
+                # Change permissions only if there is no risk of following a symlink.
+                if os.chmod in os.supports_fd:
+                    os.chmod(f.fileno(), mode)
+                elif os.chmod in os.supports_follow_symlinks:
+                    os.chmod(f.name, mode, follow_symlinks=False)
 
             replace(f.name, path)
 
+    def set(
+        self, key: str, value: bytes, expires: Union[int, datetime, None] = None
+    ) -> None:
+        path = self._get_cache_path(key)
+        self._write(path, value)
+
     def delete(self, key: str) -> None:
         path = self._get_cache_path(key)
         with suppressed_cache_errors():
             os.remove(path)
+        with suppressed_cache_errors():
+            os.remove(path + ".body")
+
+    def get_body(self, key: str) -> Optional[BinaryIO]:
+        # The cache entry is only valid if both metadata and body exist.
+        metadata_path = self._get_cache_path(key)
+        body_path = metadata_path + ".body"
+        if not (os.path.exists(metadata_path) and os.path.exists(body_path)):
+            return None
+        with suppressed_cache_errors():
+            return open(body_path, "rb")
+
+    def set_body(self, key: str, body: bytes) -> None:
+        path = self._get_cache_path(key) + ".body"
+        self._write(path, body)