Do not re-encode a UTF-8 string as ISO-8859-1 silently in HTTP requests

This issue is about sending an HTTP request, and not about the response.

    headers = { 'Content-Type': 'application/json; charset=utf-8' }
    response = requests.post(url, headers=headers, data=my_native_python3_utf8_string)

Expected Result

I expected the request to be sent as UTF-8, after all, everything in the Python 3 ecosystem uses UTF-8 by default.

Actual Result

My UTF-8 string is silently re-encoded as ISO-8859-1, causing confusing bugs at the recipient. The code in http.client is doing it:

https://github.com/python/cpython/blob/c3dd7e45cc5d36bbe2295c2840faabb5c75d83e4/Lib/http/client.py#L1312

• In my opinion, RFC 2616 Section 3.7.1 does not apply here.
• The whole Python 3 ecosystem uses UTF-8 by default, so I find it utterly confusing that a library silently re-encodes a UTF-8 string as ISO-8859-1.

Suggestion

I suggest that if requests takes a native UTF-8 string as data argument, it makes sure that it is handled as a UTF-8 string all the way, and won’t be silently re-encoded as ISO-8859-1. It can cause really obscure bugs otherwise.

Related

This issue is about sending a request. Related open issues are mostly concerned with the response:

• Remove ISO-8859-1 charset fallback
• Simplify charset handling

Reproduction Steps

See above.

System Information

$ python -m requests.help
{
  "chardet": {
    "version": "3.0.4"
  },
  "cryptography": {
    "version": "2.8"
  },
  "idna": {
    "version": "2.8"
  },
  "implementation": {
    "name": "CPython",
    "version": "3.7.4"
  },
  "platform": {
    "release": "4.15.0-107-generic",
    "system": "Linux"
  },
  "pyOpenSSL": {
    "openssl_version": "1010104f",
    "version": "19.1.0"
  },
  "requests": {
    "version": "2.22.0"
  },
  "system_ssl": {
    "version": "1010107f"
  },
  "urllib3": {
    "version": "1.25.8"
  },
  "using_pyopenssl": true
}

[baharev]

@sethmlarson

It is a best practice to provide bytes instead of str for the body so that no underlying library needs to guess at what encoding you want.

Yes, I have figured that out the hard way.

The problem is that it is incredibly easy to forget an .encode() call (accidentally pass the string unencoded). To add salt to the wound, it will even “work” with ASCII characters and you won’t even notice you have a bug (you forgot an .encode()) until you get a more exotic character in the string. Ouch.

In other words, I find the current interface a loaded gun, and you can easily shoot yourself in the foot.

Requests is under feature freeze with no room for breaking changes so this change is extremely unlikely to land, regardless of its utility.

OK, I understand.

[baharev]

@sethmlarson +1s are great, I really appreciate it, but what should I do so that this issue is eventually addressed?

If this issue remains closed, it will be forgotten.

A “fix” could be as simple as throwing TypeError if the data argument requires encoding (a string for example). I don’t think there is a fix that is not a breaking change.