Pass the session's proxies property to request (#10680)

news/9691.bugfix.rst

@@ -0,0 +1 @@
+Fix pip install issues using a proxy due to an inconsistency in how Requests is currently handling variable precedence in session.

src/pip/_internal/network/session.py

@@ -449,6 +449,8 @@ class PipSession(requests.Session):
     def request(self, method: str, url: str, *args: Any, **kwargs: Any) -> Response:
         # Allow setting a default timeout on a session
         kwargs.setdefault("timeout", self.timeout)
+        # Allow setting a default proxies on a session
+        kwargs.setdefault("proxies", self.proxies)
 
         # Dispatch the actual request
         return super().request(method, url, *args, **kwargs)

tests/conftest.py

@@ -70,6 +70,12 @@ def pytest_addoption(parser: Parser) -> None:
         default=False,
         help="run 'pip search' tests",
     )
+    parser.addoption(
+        "--proxy",
+        action="store",
+        default=None,
+        help="use given proxy in session network tests",
+    )
 
 
 def pytest_collection_modifyitems(config: Config, items: List[pytest.Item]) -> None:
@@ -628,3 +634,8 @@ def utc() -> Iterator[None]:
         tzset()
         yield
     tzset()
+
+
+@pytest.fixture
+def proxy(request: pytest.FixtureRequest) -> str:
+    return request.config.getoption("proxy")

tests/unit/test_network_session.py

@@ -1,7 +1,10 @@
 import logging
-from typing import Any, List
+from typing import Any, List, Optional
+from urllib.parse import urlparse
+from urllib.request import getproxies
 
 import pytest
+from pip._vendor import requests
 
 from pip import __version__
 from pip._internal.models.link import Link
@@ -242,3 +245,31 @@ class TestPipSession:
         actual_level, actual_message = log_records[0]
         assert actual_level == "WARNING"
         assert "is not a trusted or secure host" in actual_message
+
+    @pytest.mark.network
+    def test_proxy(self, proxy: Optional[str]) -> None:
+        session = PipSession(trusted_hosts=[])
+
+        if not proxy:
+            # if user didn't pass --proxy then try to get it from the system.
+            env_proxy = getproxies().get("http", None)
+            proxy = urlparse(env_proxy).netloc if env_proxy else None
+
+        if proxy:
+            # set proxy scheme to session.proxies
+            session.proxies = {
+                "http": f"{proxy}",
+                "https": f"{proxy}",
+                "ftp": f"{proxy}",
+            }
+
+        connection_error = None
+        try:
+            session.request("GET", "https://pypi.org", timeout=1)
+        except requests.exceptions.ConnectionError as e:
+            connection_error = e
+
+        assert connection_error is None, (
+            f"Invalid proxy {proxy} or session.proxies: "
+            f"{session.proxies} is not correctly passed to session.request."
+        )