[Typing] - HTTPError doesn't have a request attribute

[michaeloliverx]

The HTTPError class serves as a base class for RequestError and HTTPStatusError. The docstring shows the following usage:

try:
    response = httpx.get("https://www.example.com")
    response.raise_for_status()
except httpx.HTTPError as exc:
    print(f"HTTP Exception for {exc.request.url} - {exc}")

Mypy doesn't like this:

error: "HTTPError" has no attribute "request"  [attr-defined]

[florimondmanca]

Both child classes do have .request but it does seem like mypy isn't able to tell that. Should this be treated as an HTTPX issue (should we be adding request: Request annotation to HTTPError as a hint), or is this something mypy should be able to infer? Is there any open mypy ticket on a case like this?

[michaeloliverx]

The following change keeps mypy happy in my test:

class HTTPError(Exception):
    """
    Base class for `RequestError` and `HTTPStatusError`.

    Useful for `try...except` blocks when issuing a request,
    and then calling `.raise_for_status()`.

    For example:

    ```
    try:
        response = httpx.get("https://www.example.com")
        response.raise_for_status()
    except httpx.HTTPError as exc:
        print(f"HTTP Exception for {exc.request.url} - {exc}")
    ```
    """

+   request: "Request"

    def __init__(self, message: str) -> None:
        super().__init__(message)

One issue with this approach is that we are essentially lying to the type checker that HTTPError has a request attribute defined when in fact it is only the subclasses that define it. We rely on all subclasses to define that attribute (which they do atm). Perhaps it should be a real attribute on HTTPError rather than a hint?

[michaeloliverx]

There is no way mypy would be able to infer an attribute that isn't declared.

[florimondmanca]

There is no way mypy would be able to infer an attribute that isn't declared.

Well, true.

Maybe we could do this…

class HTTPError(Exception):
    def __init__(self, message: str) -> None:
        super().__init__(message)
        self._request: Optional["Request"] = None

    @property
    def request(self) -> "Request":
        if self._request is None:
            raise RuntimeError("The .request property has not been set.")
        return self._request


class RequestError(HTTPError):
    def __init__(self, message: str, *, request: "Request" = None) -> None:
        super().__init__(message)
        self._request = request

    @HTTPError.request.setter  # XXX: Does this even work???
    def request(self, request: "Request") -> None:
        self._request = request


class HTTPStatusError(HTTPError):
    def __init__(
        self, message: str, *, request: "Request", response: "Response"
    ) -> None:
        super().__init__(message)
        self._request = request
        self.response = response

Btw that setter on RequestError is used to attach the request during a request/response cycle:

httpx/httpx/_exceptions.py

Lines 336 to 339 in 3176535

	except RequestError as exc:
	if request is not None:
	exc.request = request
	raise exc

Actually currently HTTPStatusError defines .request as a public (read-write) attribute so the setter could very much be defined in HTTPError…

[michaeloliverx]

I think putting the property getter/setter on HTTPError makes sense.

[michaeloliverx]

Fixed in #2158