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Handle module scripts that include top-level await. #984

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Handle module scripts that include top-level await. #984

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32 changes: 21 additions & 11 deletions worklets/Overview.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -240,7 +240,9 @@ When a user agent is to <dfn export>create a WorkletGlobalScope</dfn>, given |wo

6. Invoke the <a>initialize a global object's CSP list</a> algorithm given |workletGlobalScope|.

7. For each |entry| in the given |moduleResponsesMap| (in insertion order), run the following
7. Let |scripts| be «».

8. For each |entry| in the given |moduleResponsesMap| (in insertion order), run the following
substeps:

1. Let |moduleURLRecord| be |entry|'s key.
Expand All @@ -249,14 +251,19 @@ When a user agent is to <dfn export>create a WorkletGlobalScope</dfn>, given |wo
|moduleResponsesMap|, |outsideSettings|, and |insideSettings| when
it asynchronously completes.

3. <a>Run a module script</a> given |script|.
3. Let |promise| be the result of <a lt="run a module script">running a module script</a>
given |script|.

4. [=list/Append=] |promise| to |scripts|.

Note: <a>Fetch a worklet script</a> won't actually perform a network request as it will hit
the worklet's <a>module responses map</a>. It also won't have a parsing error as at this
point it should have successfully been parsed by another worklet global scope. I.e.
|script| should never be null here.

6. Run the <a>responsible event loop</a> specified by |insideSettings|.
9. [=Wait for all=] |scripts|, with success steps and failure steps both given by:

1. Run the <a>responsible event loop</a> specified by |insideSettings|.
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I think this isn't right. Without an inner event loop, the microtask queue (and thus any awaits) cannot run.

I see two possible semantics here:

  • Ignore the promises returned; their errors will be reported appropriately, and that's all one would do with them.
  • Run the module scripts "sequentially", waiting for one to complete (i.e. the promise to settle) before moving on to the next.

I think the first of these is probably more correct, since (IIRC) it aligns with what happens if you have multiple TLA-using <script type=module>s.

</div>

### Script settings for worklets ### {#script-settings-for-worklets}
Expand Down Expand Up @@ -457,18 +464,21 @@ When the user agent is to <dfn>fetch and invoke a worklet script</dfn> given |wo

2. Reject |promise| with <a>error to rethrow</a>.

5. <a>Run a module script</a> given |script|.
5. Let |promise| be the result of <a lt="run a module script">running a module script</a> given
|script|.

6. <a>Queue a task</a> on |outsideSettings|'s <a>responsible event loop</a> to run these steps:
6. [=promise/React=] to |promise|:
* If |promise| was fulfilled or rejected, then:
1. <a>Queue a task</a> on |outsideSettings|'s <a>responsible event loop</a> to run these steps:

1. If |pendingTaskStruct|'s <a for="pending tasks struct">counter</a> is not <b>-1</b>, then
run these steps:
1. If |pendingTaskStruct|'s <a for="pending tasks struct">counter</a> is not <b>-1</b>, then
run these steps:

1. Decrement |pendingTaskStruct|'s <a for="pending tasks struct">counter</a> by
<b>1</b>.
1. Decrement |pendingTaskStruct|'s <a for="pending tasks struct">counter</a> by
<b>1</b>.

2. If |pendingTaskStruct|'s <a for="pending tasks struct">counter</a> is <b>0</b>, then
resolve |promise|.
2. If |pendingTaskStruct|'s <a for="pending tasks struct">counter</a> is <b>0</b>, then
resolve |promise|.
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It looks like you shadowed an existing |promise| variable.

</div>

<div algorithm>
Expand Down