[Webkit-unassigned] [Bug 198643] New: async function resolution order

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=198643

            Bug ID: 198643
           Summary: async function resolution order
           Product: WebKit
           Version: Safari 12
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: johnplaisted at google.com

Created attachment 371556

  --> https://bugs.webkit.org/attachment.cgi?id=371556&action=review

Test demonstrating differences in async / promise behavior

Steps to reproduce:

The await keyword has a different resolution order than Promises, which seems incorrect (and fwiw Chrome's await matches promises; FireFox appears to share Safari's behavior).

I think I've found two different cases where the order is different from promises:

In some cases the await order determines when functions continue (rather than the resolve() order, assuming things resolve synchronously)
In some other cases it seems to be the opposite of the resolve AND await order when the are the same order. Maybe it is because one is an await <literal> and the other is an await promise?

Actual results:

The order of asynchronous code with an async function doesn't match the equivalent promise code.

When running the file:

async test fails
promise test passes
order of await determines order of async callbacks
order resolve() determines order of promise callbacks


Expected results:

The async function order matches the Promise equivalent.

When running the file:

async test passes
promise test passes
order of resolve() determines order of async callbacks
order resolve() determines order of promise callbacks

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