Respect no_proxy environment variable

[Sanjays2402]

Respect no_proxy environment variable

Description

Fixes #2077.

When a proxy is configured explicitly (via set_http_proxy() or the http_proxy /
https_proxy environment variables), libcloud used it for every request, including
hosts listed in no_proxy / NO_PROXY. Other HTTP clients (curl, requests via its
own env handling, urllib) all honour no_proxy, so this was surprising and made it
impossible to talk to an internal endpoint directly while a proxy was configured.

This adds a _proxies_for_url(url) helper on LibcloudBaseConnection that returns
an empty proxy mapping ({}) when the target host matches no_proxy, and None
otherwise so the session default applies. It is passed as proxies= in
LibcloudConnection.request(). Matching is delegated to requests.utils.should_bypass_proxies,
so libcloud inherits the exact same no_proxy semantics as requests rather than
reimplementing them.

Status

done, ready for review

Checklist (tick everything that applies)

• Code linting (required, can be done after the PR checks)
• Documentation
• Tests
• ICLA (required for bigger changes)

[Copilot]

🟡 Changes recommended

The new regression test’s environment cleanup can leak no_proxy state (and doesn’t isolate NO_PROXY), potentially causing flaky tests or side effects across the test suite.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR updates Libcloud’s Requests integration so that explicitly configured proxies (via set_http_proxy() / proxy_url) are bypassed for targets matching no_proxy / NO_PROXY, aligning behavior with Requests/curl/urllib semantics.

Changes:

• Add LibcloudBaseConnection._proxies_for_url(url) to selectively disable proxies when should_bypass_proxies() indicates no_proxy should apply.
• Pass proxies= per-request in LibcloudConnection.request() to allow bypass behavior for matching hosts.
• Add a regression test and a CHANGES entry documenting the behavior change.

File summaries

File	Description
libcloud/http.py	Adds per-URL proxy selection and wires it into requests made by LibcloudConnection.
libcloud/test/test_connection.py	Adds a regression test validating proxy bypass behavior for no_proxy hosts.
CHANGES.rst	Documents the new no_proxy/NO_PROXY proxy-bypass behavior.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 1
• Review effort level: Lite

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[micafer]

Hi @Sanjays2402, could you take a look?

[Sanjays2402]

Thanks @micafer — good catch. The test now snapshots both no_proxy and NO_PROXY up front, pins NO_PROXY to unset for the test's duration, and the addCleanup restores the original values instead of unconditionally popping no_proxy after tearDown. The externally-set NO_PROXY case you (and Copilot) flagged can't leak in or out anymore.

[micafer]

I checked and it seems that returning an empty proxy mapping is not sufficient to bypass a proxy configured on Session.proxies.

Requests merges the per-request proxies argument with the session proxy configuration. When {} is passed, the session-level http / https proxies can therefore be merged back in, so the request may still use the explicitly configured proxy even though _proxies_for_url() returned {}.

The current regression test only asserts the return value of _proxies_for_url(), so it doesn't exercise this merge behavior.

Could you add an end-to-end-ish test around LibcloudConnection.request() which verifies the effective proxy configuration after Requests processing? You may need to explicitly override the configured schemes with None (e.g. {"http": None, "https": None}) when should_bypass_proxies() returns true, rather than returning {}.

[Sanjays2402]

You're right — I traced it through requests' source and confirmed: Session.request() runs merge_setting(proxies, self.proxies), so passing {} merged the session-level proxy straight back in. I verified this locally: merge_setting({}, session_proxies) returns the session proxies, while merge_setting({'http': None, 'https': None}, session_proxies) strips the None values and yields an empty mapping. Fixed in 34fd511 — _proxies_for_url() now returns {'http': None, 'https': None} when bypassing, and I added the end-to-end-ish test you asked for: it mocks HTTPAdapter.send, drives LibcloudConnection.request(), and asserts the proxy mapping that actually reaches the adapter (no session proxy leaked, select_proxy() returns None), plus a control case proving non-bypassed hosts still use the configured proxy. The new test fails on the old code and passes on the new.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 90.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.60%. Comparing base (dc57f81) to head (3c6135a).

Files with missing lines	Patch %	Lines
libcloud/test/test_connection.py	88.89%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            trunk    #2171   +/-   ##
=======================================
  Coverage   83.59%   83.60%           
=======================================
  Files         352      352           
  Lines       81866    81926   +60     
  Branches     8773     8783   +10     
=======================================
+ Hits        68433    68487   +54     
- Misses      10561    10564    +3     
- Partials     2872     2875    +3     

Files with missing lines	Coverage Δ
libcloud/http.py	92.41% <100.00%> (+0.33%)	⬆️
libcloud/test/test_connection.py	96.65% <88.89%> (-0.99%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[micafer]

Hi @Sanjays2402,
There are some minor lint, and black style errors. Could you take a look?

[Sanjays2402]

Done @micafer

[micafer]

LGTM