[BUG] Disabled proxy resulting in general RequestsError 400

[vdusek]

Describe the bug

• When the proxy I'm using is disabled, the execution results in the general RequestsError exception with "CONNECT tunnel failed, response 400".
• This is bad because I cannot detect that the error has something to do with my proxy.

To Reproduce

• Using proxy.py as proxy server.

import asyncio
from curl_cffi.requests import AsyncSession
from proxy import Proxy

async def main():
    session = AsyncSession()

    with Proxy(
        [
            '--hostname',
            '127.0.0.1',
            '--port',
            '8899',
            '--basic-auth',
            'username:password',
            '--disable-http-proxy',
        ]
    ):
        response = await session.request(
            'get',
            'https://httpbin.org/get',
            proxy='http://username:password@127.0.0.1:8899',
        )
        print(f'status_code: {response.status_code}')
        print(f'content: {response.content[:1000].decode()}')

if __name__ == '__main__':
    asyncio.run(main())

Resulting in:

$ python run_curl_cffi_bug.py 
2024-08-01 16:45:33,542 - pid:312119 [I] plugins.load:89 - Loaded plugin proxy.http.proxy.auth.AuthPlugin
Traceback (most recent call last):
  File "/home/vdusek/Projects/crawlee-py/.venv/lib64/python3.12/site-packages/curl_cffi/requests/session.py", line 1264, in request
    await task
curl_cffi.curl.CurlError: Failed to perform, curl: (56) CONNECT tunnel failed, response 400. See https://curl.se/libcurl/c/libcurl-errors.html first for more details.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/vdusek/Projects/crawlee-py/run_curl_cffi_bug.py", line 31, in <module>
    asyncio.run(main())
  File "/usr/lib64/python3.12/asyncio/runners.py", line 194, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.12/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.12/asyncio/base_events.py", line 687, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/home/vdusek/Projects/crawlee-py/run_curl_cffi_bug.py", line 21, in main
    response = await session.request(
               ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/vdusek/Projects/crawlee-py/.venv/lib64/python3.12/site-packages/curl_cffi/requests/session.py", line 1268, in request
    raise RequestsError(str(e), e.code, rsp) from e
curl_cffi.requests.errors.RequestsError: Failed to perform, curl: (56) CONNECT tunnel failed, response 400. See https://curl.se/libcurl/c/libcurl-errors.html first for more details.

Expected behavior

• Some proxy-error-specific exceptions should be raised. HTTPX could serve as an inspiration.

Example in HTTPX:

import asyncio
from httpx import AsyncClient
from proxy import Proxy

async def main():
    with Proxy(
        [
            '--hostname',
            '127.0.0.1',
            '--port',
            '8899',
            '--basic-auth',
            'username:password',
            '--disable-http-proxy',
        ]
    ):
        async with AsyncClient(proxy='http://username:password@127.0.0.1:8899') as client:
            response = await client.get(url='https://httpbin.org/get')
            print(f'status_code: {response.status_code}')
            print(f'content: {response.read()[:1000].decode()}')

if __name__ == '__main__':
    asyncio.run(main())

Results in:

httpx.ProxyError: 400 BAD REQUEST

Versions

• curl_cffi version: 0.7.1
• proxy.py version: 2.4.4
• httpx version: 0.27.0

[coletdjnz]

currently, curl-cffi only has one general error for all curl errors. Adding support for mapping curl errors into Python errors would be a nice addition.

For now, the way of detecting certain errors is by using the curl error code. However for this particular error, curl does not appear to distinguish the proxy error by a code so you have to do a string match in addition to code check.

An example from our project: https://github.com/yt-dlp/yt-dlp/blob/master/yt_dlp%2Fnetworking%2F_curlcffi.py#L241

[perklet]

Progress is tracked in #250.