`handleWasmStreaming` is the function that provides the binding with
the `fetch` API needed for `WebAssembly.instantiateStreaming()` and
`WebAssembly.compileStreaming()`. When I implemented it in #11200, I
thought V8 was calling these functions with the argument of the
`WebAssembly` streaming functions, without doing any resolving, and so
`handleWasmStreaming` awaits for the parameter to resolve. However,
as discovered in
https://github.com/denoland/deno/issues/13917#issuecomment-1065805565,
V8 does in fact resolve the parameter if it's a promise (and handles
rejections arising from that).
This change removes the `async` IIFE inside `handleWasmStreaming`,
letting initial errors be handled synchronously (which will however
not throw synchronously from the `WebAssembly` namespace functions).
Awaiting is still necessary for reading the bytes of the response,
though, and so there is an `async` IIFE for that.
When an exception is thrown during the processing of streaming WebAssembly,
`op_wasm_streaming_abort` is called. This op calls into V8, which synchronously
rejects the promise and calls into the promise rejection handler, if applicable.
But calling an op borrows the isolate's `JsRuntimeState` for the duration of the
op, which means it is borrowed when V8 calls into `promise_reject_callback`,
which tries to borrow it again, panicking.
This change changes `op_wasm_streaming_abort` from an op to a binding
(`Deno.core.abortWasmStreaming`). Although that binding must borrow the
`JsRuntimeState` in order to access the `WasmStreamingResource` stored in the
`OpTable`, it also takes ownership of that `WasmStreamingResource` instance,
which means it can drop any borrows of the `JsRuntimeState` before calling into
V8.
Fetching of local files, added in #12545, returns a response with no
headers, including the `Content-Type` header. This currently makes it
not work with the WebAssembly streaming APIs, which require the response
to have a content type of `application/wasm`.
Since the only way to obtain a `Response` object with a non-empty `url`
field is via `fetch()`, this change changes the content type requirement
to only apply to responses whose url has the `file:` scheme.
This allows resources to be "streams" by implementing read/write/shutdown. These streams are implicit since their nature (read/write/duplex) isn't known until called, but we could easily add another method to explicitly tag resources as streams.
`op_read/op_write/op_shutdown` are now builtin ops provided by `deno_core`
Note: this current implementation is simple & straightforward but it results in an additional alloc per read/write call
Closes #12556
WebAssembly modules compiled through `WebAssembly.compile()` and similar
non-streaming APIs don't have a URL associated to them, because they
have been compiled from a buffer source. In stack traces, V8 will use
a URL such as `wasm://wasm/d1c677ea`, with a hash of the module.
However, wasm modules compiled through streaming APIs, like
`WebAssembly.compileStreaming()`, do have a known URL, which can be
obtained from the `Response` object passed into the streaming APIs. And
as per the developer-facing display conventions in the WebAssembly
Web API spec, this URL should be used in stack traces. This change
implements that.
Async WebAssembly compilation was implemented by adding two
bindings: `set_wasm_streaming_callback`, which registered a callback to
be called whenever a streaming wasm compilation was started, and
`wasm_streaming_feed`, which let the JS callback modify the state of the
v8 wasm compiler.
`set_wasm_streaming_callback` cannot currently be implemented as
anything other than a binding, but `wasm_streaming_feed` does not really
need to use anything specific to bindings, and could indeed be
implemented as one or more ops. This PR does that, resulting in a
simplification of the relevant code.
There are three operations on the state of the v8 wasm compiler that
`wasm_streaming_feed` allowed: feeding new bytes into the compiler,
letting it know that there are no more bytes coming from the network,
and aborting the compilation. This PR provides `op_wasm_streaming_feed`
to feed new bytes into the compiler, and `op_wasm_streaming_abort` to
abort the compilation. It doesn't provide an op to let v8 know that the
response is finished, but closing the resource with `Deno.core.close()`
will achieve that.
In the spec, a URL record has an associated "blob URL entry", which for
`blob:` URLs is populated during parsing to contain a reference to the
`Blob` object that backs that object URL. It is this blob URL entry that
the `fetch` API uses to resolve an object URL.
Therefore, since the `Request` constructor parses URL inputs, it will
have an associated blob URL entry which will be used when fetching, even
if the object URL has been revoked since the construction of the
`Request` object. (The `Request` constructor takes the URL as a string
and parses it, so the object URL must be live at the time it is called.)
This PR adds a new `blobFromObjectUrl` JS function (backed by a new
`op_blob_from_object_url` op) that, if the URL is a valid object URL,
returns a new `Blob` object whose parts are references to the same Rust
`BlobPart`s used by the original `Blob` object. It uses this function to
add a new `blobUrlEntry` field to inner requests, which will be `null`
or such a `Blob`, and then uses `Blob.prototype.stream()` as the
response's body. As a result of this, the `blob:` URL resolution from
`op_fetch` is now useless, and has been removed.
The streaming WASM support code inspects the Response object's
Content-Type header but if that was missing, it failed with a fairly
inscrutable "String.prototype.toLowerCase called on null or undefined"
exception. Now it raises a more legible "Invalid WebAssembly content
type" exception.
