For non-streaming cases, populate request.content automatically.

[tomchristie]

Minor user-experience & consistency tweak.

For non-streaming cases we should pre-load request.content.

This leads to neater consistency between requests/responses, and ensures that the request content is readily accessible to introspection.

>>> r = httpx.Request("POST", "https://www.example.com", content=b'...')
>>> r.content  # Previously this would raise 'httpx.RequestNotRead'
b'...'

>>> r = httpx.Request("POST", "https://www.example.com", json={"example": "payload"})
>>> r.content  # Previously this would raise 'httpx.RequestNotRead'
b'{"example": "payload"}'

>>> r = httpx.Request("POST", "https://www.example.com", content=[b'.' for i in range(3)])
>>> r.content
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/tomchristie/GitHub/encode/httpx/httpx/_models.py", line 865, in content
    raise RequestNotRead()
httpx.RequestNotRead: Attempted to access streaming request content, without having called `read()`.

Or, eg...

Previously...

>>> import httpx
>>> r = httpx.get("https://www.example.com")
>>> r.request.content
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/tomchristie/GitHub/encode/httpx/httpx/_models.py", line 862, in content
    raise RequestNotRead()
httpx.RequestNotRead: Attempted to access request content, without having called `read()`  # Eh?

Now...

>>> import httpx
>>> r = httpx.get("https://www.example.com")
>>> r.request.content
b''

[tomchristie]

Going to push on with this sans-review, because it'll otherwise block other bits of work that I'd like to push on with here.

[lundberg]

Much nicer 👍

Not sure, but maybe the httpx.RequestNotRead and httpx.ResponseNotRead should be renamed to align with #1584, e.g. turn both into a httpx.StreamNotRead?

[tomchristie]

Interesting yup. Hierarchy feels nicer that way for sure.