iter_bytes raise ValueError when response body is empty

[heroesm]

Code to reproduce:

import httpx
import respx

from httpx import Response


@respx.mock
def test_example():
    respx.get("https://example.org/").mock(return_value=Response(200))
    response = httpx.get("https://example.org/")
    assert response.status_code == 200
    assert response.text == ''
    for chunk in response.iter_bytes():
        print(chunk)

Expcted result:

No error

Real result:

  File ".../httpx/_models.py", line 1491, in iter_bytes
    for i in range(0, len(self._content), chunk_size):
ValueError: range() arg 3 must not be zero

Related source code

httpx/httpx/_models.py

Line 1491 in acb5e6a

for i in range(0, len(self._content), chunk_size):

The async version aiter_bytes also has the problem.

httpx/httpx/_models.py

Line 1589 in acb5e6a

for i in range(0, len(self._content), chunk_size):

[lovelydinosaur]

Well caught, yup. I can also duplicate it without respx like so...

import httpx

transport = httpx.MockTransport(handler=lambda request: httpx.Response(204))
client = httpx.Client(transport=transport)
response = client.get('https://www.example.com/')
for chunk in response.iter_bytes():
    print(chunk)

[lovelydinosaur]

Or indeed, more simply as...

import httpx

response = httpx.Response(200, content=b'')
for chunk in response.iter_bytes():
    print(chunk)

[lovelydinosaur]

Addressing this in #1827