[Webkit-unassigned] [Bug 242740] New: Cannot access uninitialized variable when multiple modules are simultaneously importing a module containing a top-level await

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=242740

            Bug ID: 242740
           Summary: Cannot access uninitialized variable when multiple
                    modules are simultaneously importing a module
                    containing a top-level await
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Keywords: BrowserCompat, HasReduction
          Severity: Normal
          Priority: P2
         Component: New Bugs
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: ardtimmerman+webkit at gmail.com

Created attachment 460889

  --> https://bugs.webkit.org/attachment.cgi?id=460889&action=review

Test case reduction -- also includes a README explaining the steps to reproduce the issue

When modules are simultaneously fetching an import which requires some setup time due to top-level await, one of the imports will be rejected. This doesn't happen when the modules are fetched sequentially.

Note, I'm not aware of what the spec has to say about how this should be implemented, but I did note that this behavior is not consistent with other browsers. When running the attached test case reduction on either chrome or firefox, none of the promises will be rejected.


(reproduced this using WebKit 16612(.3.6.1.8))

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