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.
Capture the incoming reason argument to
transform_stream_default_source_cancel_algorithm() on the
on_fulfilled_callback() of WebIDL::react_to_promise() on step 7.
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.
We enqueue a microtask for this readable stream AO, and the methods that
we call from the chunk steps manipulate promises. As such, we need to
enable callbacks for the entire microtask's temporary execution
context.
ReadLoopReadRequest::on_chunk expects an UInt8Array, so make sure we
convert the passed in ByteBuffer to an UInt8Array before passing it to
the AO writable_stream_default_writer_write.
Co-authored-by: Timothy Flynn <trflynn89@pm.me>
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>.
This changes the signature of queue_a_microtask() from AK:Function to
JS::HeapFunction to be more clear to the user of the functions that this
is what is used internally.
Switching away from SafeFunction immediately backfired here, as we're
dealing with two layers of captures, not one.
Let's do the correct fix, which is to use HeapFunction. This makes the
API and its behavior explicit, and keeps captures alive as long as the
HeapFunction is alive.
Fixes#23819.
Now that these algorithms are a HeapFunction as opposed to SafeFunction,
the problem mentioned in the FIXME is no longer applicable as these
functions are GC-allocated like everything else.
