[Webkit-unassigned] [Bug 150358] Support for promise rejection events (unhandledrejection)

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=150358

--- Comment #8 from Yusuke Suzuki <utatane.tea at gmail.com> ---
Comment on attachment 295505
  --> https://bugs.webkit.org/attachment.cgi?id=295505
[PATCH] Work in Progress

View in context: https://bugs.webkit.org/attachment.cgi?id=295505&action=review

Awesome. Early stage review.

> Source/JavaScriptCore/builtins/PromiseOperations.js:109
> +        @hostPromiseRejectionTracker(promise, "reject");

I recommend using some bytecode intrinsic constants instead of the string `"reject"`.
For example, @promiseStatePending is represented as a bytecode intrinsic constant.
The benefit of the bytecode intrinsic constant is we can share the same value in C++ and JS.
You can see how to define it in bytecode/BytecodeIntrinsicRegistry.h.

> Source/JavaScriptCore/builtins/PromisePrototype.js:62
> +            @hostPromiseRejectionTracker(promise, "handle");

Ditto.

> Source/JavaScriptCore/runtime/JSGlobalObject.h:167
> +enum class JSPromiseRejectionOperation {
> +    Reject, // When a promise is rejected without any handlers.
> +    Handle, // When a handler is added to a rejected promise for the first time.
> +};

You can expose these enums directly to the JS world through bytecode intrinsic constants.

> Source/JavaScriptCore/runtime/JSGlobalObjectFunctions.cpp:940
> +    JSPromiseRejectionOperation operation;
> +    if (operationString == "reject")
> +        operation = JSPromiseRejectionOperation::Reject;
> +    else {
> +        ASSERT(operationString == "handle");
> +        operation = JSPromiseRejectionOperation::Handle;
> +    }

And then, you can just `static_cast<>()` the argument's number to the enum.

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