Fix/invalid url handling - issue 1832

[rodrigobnogueira]

Fix Inconsistent Invalid URL Handling (Closes #1832 )

Summary

Fixed an inconsistency where URLs with a scheme but no host (e.g., https:/[google.com](http://google.com/)) raised UnsupportedProtocol instead of InvalidURL.

Problem

Previously, malformed URLs were handled inconsistently:

• httpx.get('[https://😇](about:blank)') → InvalidURL (Correct)
• httpx.get('https:/[google.com](http://google.com/)') → UnsupportedProtocol (Incorrect)

This occurred because https:/[google.com](http://google.com/) (missing one slash) parses as a URL with a scheme but an empty host. Since it lacks a host, it's treated as a relative URL, which httpcore then rejects as an unsupported protocol.

Solution

Added validation in httpx._client.Client._merge_url to explicitly check for URLs that have a scheme but no host. These are now correctly identified as invalid, raising InvalidURL with a descriptive error message.

Changes

• Modified httpx/_client.py: Added InvalidURL check in _merge_url
• Added tests/client/test_invalid_url.py: Regression tests for https:/[google.com](http://google.com/) and [https:///google.com](about:blank)

Verification

• Added new regression tests passing locally
• Existing tests pass
• Linting and type checking pass

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.