Enum CancelSupport 

pub enum CancelSupport {
    None,
    Supported,
}

Whether dropping the future returned by Transport::execute stops the exchange — see that method’s doc comment for the contract itself, of which this enum is the one honest way out.

Why two variants and not three

A third variant could split Supported by who performs the cancellation: the transport tearing down a socket it owns, versus the transport asking an ambient host to stop. It is not here because no caller decision turns on the difference. A capability answers a question the caller actually asks — here, “can I rely on a drop ending the exchange?” — and who ends it is an implementation detail. Both shapes give a guarantee of exactly the same strength, including its limit: bytes already sent are already sent, and the server may have acted on them either way.

The distinction is worth knowing even though it is not worth a variant: hclient-native owns the socket and closes it itself, while hclient-fetch and hclient-wasi ask the browser and the wasi:http host — AbortController::abort() and the Component Model’s subtask.cancel. Only the first kind can pool connections, which is why the pool lives in hclient-native and nowhere else.

Not #[non_exhaustive], deliberately: no other enum in this file is, and consistency across the capability set is worth more than reserving the right to add a variant to this one alone.

Variants

None

Dropping the future does not stop the exchange: it may run to completion, unobserved, on a connection this transport no longer reports on.

The conservative base — Capabilities::default() returns this — and here, unlike RedirectSupport::None, that costs nothing. A default must never be stronger than the truth: a backend that never touches this field is read as “do not rely on a drop stopping anything”, which is the safe reading of silence and is also exactly what a backend that genuinely cannot cancel means. The two coincide, so there is nothing to tell apart — whereas for redirects they did not: None there is a substantive “redirects are impossible”, which is a far stronger claim than “the field was not filled in”, and a transparent backend forced to say it was misread.

Supported

Dropping the future stops the exchange, as far as this transport controls it.

What that does and does not promise is the contract on Transport::execute; the short version is that our side stops, and the server’s side is not ours to promise anything about.

Trait Implementations

impl Clone for CancelSupport

fn clone(&self) -> CancelSupport

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for CancelSupport

impl Debug for CancelSupport

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for CancelSupport

fn default() -> CancelSupport

Returns the “default value” for a type.

impl Eq for CancelSupport

impl PartialEq for CancelSupport

fn eq(&self, other: &CancelSupport) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for CancelSupport