This change also removes as much direct use of JS::Promise in LibWeb
as possible. When specs refer to `Promise<T>` they should be assumed
to be referring to the WebIDL Promise type, not the JS::Promise type.
The one exception is the HostPromiseRejectionTracker hook on the JS
VM. This facility and its associated sets and events are intended to
expose the exact opaque object handles that were rejected to author
code. This is not possible with the WebIDL Promise type, so we have
to use JS::Promise or JS::Object to hold onto the promises.
It also exposes which specs need some updates in the area of
promises. WebDriver stands out in this regard. WebAudio could use
some more cross-references to WebIDL as well to clarify things.
When the min option is given the read will only be fulfilled when there
are min or more elements available in the readable byte stream.
When the min option is not given the default value for min is 1.
This AO can be used instead of CreateReadableStream in cases where we
need to set up a newly allocated ReadableStream before initialization of
said ReadableStream, i.e. ReadableStream is captured by lambdas in an
uninitialized state.
There were several instances where the spec marks an AO invocation as
infallible, but we were propagating WebIDL::ExceptionOr. These mostly
cannot throw due to knowledge about the values they are provided. By
unwinding these, we can remove a decent amount of exception handling.
There are a number of script-provided stream callbacks for various
stream operations, such as `start`, `pull`, `cancel`, etc. Out of all of
these, only the `start` callback can actually throw. And when it does,
the exception is realized immediately in the corresponding stream
constructor.
All other callbacks have spec text of the form:
Throwing an exception is treated the same as returning a rejected
promise.
And indeed this is internally handled by the streams spec. Thus all of
those callbacks can be specified as returning only a promise, rather
than a WebIDL::ExceptionOr<Promise>.
We were previously only returning the controllers current
[[byobRequest]] instead of taking into account pending pull intos.
Rename the getter function which would return the controllers
[[byobRequest]] slot to `raw_byob_request` to differentiate it from
the IDL getter.
This also leaves a FIXME for a spec step which we are also not currently
implementing correctly.
This is effectively identical to ReadableStreamAddReadRequest besides
from the fact that it takes a ReadIntoRequest instead of a ReadRequest,
and is instead intended to be used for BYOB readers.
Make it more obvious in the function signature that this function will
be taking a GC ref to a ReadRequest by appending it to the
ReadableStreams pending read requests.
