add --no-proxy option

news/5378.feature.rst

@@ -0,0 +1 @@
+Add ``--no-proxy`` option to bypass http proxy.  Using this option will ignore any configured http proxies, including any environmental variables

src/pip/_internal/cli/cmdoptions.py

@@ -274,6 +274,15 @@ class PipOption(Option):
     help="Specify a proxy in the form scheme://[user:passwd@]proxy.server:port.",
 )
 
+no_proxy: Callable[..., Option] = partial(
+    Option,
+    "--no-proxy",
+    dest="no_proxy",
+    action="store_true",
+    default=False,
+    help="Ignore all configured proxy settings, including environmental variables.",
+)
+
 retries: Callable[..., Option] = partial(
     Option,
     "--retries",
@@ -1048,6 +1057,7 @@ def check_list_path_option(options: Values) -> None:
         no_input,
         keyring_provider,
         proxy,
+        no_proxy,
         retries,
         timeout,
         exists_action,

src/pip/_internal/cli/index_command.py

@@ -124,6 +124,19 @@ def _build_session(
             }
             session.trust_env = False
 
+        # Handle no proxy option
+        if options.no_proxy:
+            # Handle case of both --no-proxy being set along with --proxy=<proxy>.
+            # In this case, the proxies from the environmental variables will be
+            # ignored, but the command line proxy will be used.
+            http_proxy = options.proxy if options.proxy else None
+            https_proxy = options.proxy if options.proxy else None
+            session.proxies = {
+                "http": http_proxy,
+                "https": https_proxy,
+            }
+            session.trust_env = False
+
         # Determine if we can prompt the user for authentication or not
         session.auth.prompting = not options.no_input
         session.auth.keyring_provider = options.keyring_provider

tests/conftest.py

@@ -96,6 +96,12 @@ def pytest_addoption(parser: Parser) -> None:
         default=None,
         help="use given proxy in session network tests",
     )
+    parser.addoption(
+        "--no-proxy",
+        action="store_true",
+        default=False,
+        help="ignore any configured proxies in session network tests",
+    )
     parser.addoption(
         "--use-zipapp",
         action="store_true",

tests/unit/test_network_session.py

@@ -1,7 +1,7 @@
 import logging
 import os
 from pathlib import Path
-from typing import Any, List, Optional
+from typing import Any, List, Optional, Union
 from urllib.parse import urlparse
 from urllib.request import getproxies
 
@@ -282,3 +282,39 @@ def test_proxy(self, proxy: Optional[str]) -> None:
             f"Invalid proxy {proxy} or session.proxies: "
             f"{session.proxies} is not correctly passed to session.request."
         )
+
+    @pytest.mark.network
+    def test_no_proxy(self) -> None:
+        def _set_no_proxy(session: PipSession) -> PipSession:
+            """Mimic logic for command line `no_proxy` option"""
+            session.trust_env = False
+            session.proxies = {
+                "http": None,
+                "https": None,
+            }
+            return session
+
+        session = PipSession(trusted_hosts=[])
+
+        connection_error_http: Union[requests.exceptions.RequestException, None] = None
+        # setup with known bad (hopefully) http proxy, and then test connection
+        # expecting a failure if the proxy is used
+        with requests.utils.set_environ("http_proxy", "http://127.0.0.1:88888"):
+            try:
+                session = _set_no_proxy(session)
+                session.request("GET", "https://pypi.org", timeout=1)
+            except requests.exceptions.ConnectionError as e:
+                connection_error_http = e
+
+        connection_error_https: Union[requests.exceptions.RequestException, None] = None
+        # setup with known bad (hopefully) https proxy, and then test connection
+        # expecting a failure if the proxy is used
+        with requests.utils.set_environ("https_proxy", "http://127.0.0.1:65534"):
+            try:
+                session = _set_no_proxy(session)
+                session.request("GET", "https://pypi.org", timeout=1)
+            except requests.exceptions.ConnectionError as e:
+                connection_error_https = e
+
+        assert connection_error_http is None, "Unexpected use of http proxy"
+        assert connection_error_https is None, "Unexpected use of https proxy"

tests/unit/test_options.py

@@ -523,6 +523,13 @@ def test_proxy(self) -> None:
         )
         assert options1.proxy == options2.proxy == "path"
 
+    def test_no_proxy(self) -> None:
+        # FakeCommand intentionally returns the wrong type.
+        options1, _ = cast(Tuple[Values, List[str]], main(["--no-proxy", "fake"]))
+        options2, _ = cast(Tuple[Values, List[str]], main(["fake", "--no-proxy"]))
+        assert options1.no_proxy
+        assert options2.no_proxy
+
     def test_retries(self) -> None:
         # FakeCommand intentionally returns the wrong type.
         options1, args1 = cast(