feat(provider): use standard library to get proxies (#426)

Fixes #422

craft_application/services/provider.py

@@ -22,6 +22,8 @@
 import pathlib
 import pkgutil
 import sys
+import urllib.request
+from collections.abc import Generator, Iterable
 from pathlib import Path
 from typing import TYPE_CHECKING
 
@@ -36,16 +38,14 @@
 from craft_application.util import platforms, snap_config
 
 if TYPE_CHECKING:  # pragma: no cover
-    from collections.abc import Generator
-
     import craft_providers
 
     from craft_application import models
     from craft_application.application import AppMetadata
     from craft_application.services import ServiceFactory
 
 
-DEFAULT_FORWARD_ENVIRONMENT_VARIABLES = ("http_proxy", "https_proxy", "no_proxy")
+DEFAULT_FORWARD_ENVIRONMENT_VARIABLES: Iterable[str] = ()
 
 
 class ProviderService(base.ProjectService):
@@ -93,6 +93,10 @@ def setup(self) -> None:
             if name in os.environ:
                 self.environment[name] = os.getenv(name)
 
+        for scheme, value in urllib.request.getproxies().items():
+            self.environment[f"{scheme.lower()}_proxy"] = value
+            self.environment[f"{scheme.upper()}_PROXY"] = value
+
         if self._install_snap:
             channel = (
                 None

tests/unit/services/test_provider.py

@@ -30,6 +30,59 @@
 from craft_providers.actions.snap_installer import Snap
 
 
+@pytest.mark.parametrize(
+    ("given_environment", "expected_environment"),
+    [
+        ({}, {}),
+        ({"http_proxy": "thing"}, {"http_proxy": "thing", "HTTP_PROXY": "thing"}),
+        ({"HTTP_PROXY": "thing"}, {"http_proxy": "thing", "HTTP_PROXY": "thing"}),
+        ({"ssh_proxy": "thing"}, {"ssh_proxy": "thing", "SSH_PROXY": "thing"}),
+        ({"no_proxy": "thing"}, {"no_proxy": "thing", "NO_PROXY": "thing"}),
+        ({"NO_PROXY": "thing"}, {"no_proxy": "thing", "NO_PROXY": "thing"}),
+        # Special case handled by upstream:
+        # https://docs.python.org/3/library/urllib.request.html#urllib.request.getproxies
+        (
+            {
+                "REQUEST_METHOD": "GET",
+                "HTTP_PROXY": "thing",
+            },
+            {},
+        ),
+        (  # But lower-case http_proxy is still allowed
+            {
+                "REQUEST_METHOD": "GET",
+                "http_proxy": "thing",
+            },
+            {"http_proxy": "thing", "HTTP_PROXY": "thing"},
+        ),
+    ],
+)
+def test_setup_proxy_environment(
+    monkeypatch: pytest.MonkeyPatch,
+    app_metadata,
+    fake_services,
+    fake_project,
+    fake_build_plan,
+    given_environment: dict[str, str],
+    expected_environment: dict[str, str],
+):
+    for var, value in given_environment.items():
+        monkeypatch.setenv(var, value)
+
+    expected_environment |= {"CRAFT_MANAGED_MODE": "1"}
+
+    service = provider.ProviderService(
+        app_metadata,
+        fake_services,
+        project=fake_project,
+        work_dir=pathlib.Path(),
+        build_plan=fake_build_plan,
+    )
+    service.setup()
+
+    assert service.environment == expected_environment
+
+
 @pytest.mark.parametrize(
     ("install_snap", "environment", "snaps"),
     [