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Normative: Propagate active ScriptOrModule with JobCallback Record #3195

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Normative: Propagate active ScriptOrModule with JobCallback Record #3195

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40 changes: 36 additions & 4 deletions spec.html
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Original file line number Diff line number Diff line change
Expand Up @@ -11901,6 +11901,17 @@ <h1>JobCallback Records</h1>
The function to invoke when the Job is invoked.
</td>
</tr>
<tr>
<td>
[[ScriptOrModule]]
</td>
<td>
a Script Record or a Module Record
</td>
<td>
The script or module in which the Job was created.
</td>
</tr>
<tr>
<td>
[[HostDefined]]
Expand All @@ -11926,16 +11937,27 @@ <h1>
</dl>
<p>An implementation of HostMakeJobCallback must conform to the following requirements:</p>
<ul>
<li>It must return a JobCallback Record whose [[Callback]] field is _callback_.</li>
<li>It must return a JobCallback Record whose [[Callback]] field is _callback_, and [[ScriptOrModule]] field is the result of GetActiveScriptOrModule().</li>
</ul>
<p>The default implementation of HostMakeJobCallback performs the following steps when called:</p>
<emu-alg>
1. Return the JobCallback Record { [[Callback]]: _callback_, [[HostDefined]]: ~empty~ }.
1. Let _scriptOrModule_ be GetActiveScriptOrModule().
1. Return the JobCallback Record { [[Callback]]: _callback_, [[ScriptOrModule]]: _scriptOrModule_, [[HostDefined]]: ~empty~ }.
</emu-alg>
<p>ECMAScript hosts that are not web browsers must use the default implementation of HostMakeJobCallback.</p>
<emu-note>
<p>This is called at the time that the callback is passed to the function that is responsible for its being eventually scheduled and run. For example, `promise.then(thenAction)` calls MakeJobCallback on `thenAction` at the time of invoking `Promise.prototype.then`, not at the time of scheduling the reaction Job.</p>
</emu-note>

<emu-note>
<p>An example of when _scriptOrModule_ is not *null*, and saving it in this way is useful, is the following:</p>

<pre><code class="javascript">Promise.resolve('import(`./example.mjs`)').then(eval);</code></pre>

<p>Without this step (and the steps that use it in HostCallJobCallback), the result of GetActiveScriptOrModule() would be *null* when the <emu-xref href="#sec-import-calls">`import()`</emu-xref> call is evaluated, since <emu-xref href="#sec-eval-x">`eval()`</emu-xref> is a built-in function that does not originate from any particular script.</p>

<p>With this step in place, the active _scriptOrModule_ is propagated from the above code into the job, allowing the <emu-xref href="#sec-import-calls">`import()`</emu-xref> call to use the original script's base URL appropriately.</p>
</emu-note>
</emu-clause>

<emu-clause id="sec-hostcalljobcallback" type="host-defined abstract operation">
Expand All @@ -11950,6 +11972,7 @@ <h1>
</dl>
<p>An implementation of HostCallJobCallback must conform to the following requirements:</p>
<ul>
<li>It must perform implementation-defined steps such that _jobCallback_.[[ScriptOrModule]] is the <emu-xref href="#job-activescriptormodule">active script or module</emu-xref> at the time of _job_'s invocation.</li>
<li>It must perform and return the result of Call(_jobCallback_.[[Callback]], _V_, _argumentsList_).</li>
</ul>
<emu-note>
Expand All @@ -11958,7 +11981,17 @@ <h1>
<p>The default implementation of HostCallJobCallback performs the following steps when called:</p>
<emu-alg>
1. Assert: IsCallable(_jobCallback_.[[Callback]]) is *true*.
1. Return ? Call(_jobCallback_.[[Callback]], _V_, _argumentsList_).
1. Let _callerContext_ be the running execution context.
1. If _callerContext_ is not already suspended, suspend _callerContext_.
1. Let _jobContext_ be a new execution context.
1. Let _scriptOrModule_ be _jobCallback_.[[ScriptOrModule]].
1. If _scriptOrModule_ is not *null*, then
1. Set the Realm of _jobContext_ to _scriptOrModule_.[[Realm]].
1. Set the ScriptOrModule of _jobContext_ to _scriptOrModule_.
1. Perform any necessary implementation-defined initialization of _jobContext_.
1. Let _result_ be Completion(Call(_jobCallback_.[[Callback]], _V_, _argumentsList_)).
1. Remove _jobContext_ from the execution context stack and restore _callerContext_ as the running execution context.
1. Return ? _result_.
</emu-alg>
<p>ECMAScript hosts that are not web browsers must use the default implementation of HostCallJobCallback.</p>
</emu-clause>
Expand Down Expand Up @@ -11992,7 +12025,6 @@ <h1>
<p>An implementation of HostEnqueuePromiseJob must conform to the requirements in <emu-xref href="#sec-jobs"></emu-xref> as well as the following:</p>
<ul>
<li>If _realm_ is not *null*, each time _job_ is invoked the implementation must perform implementation-defined steps such that execution is <emu-xref href="#job-preparedtoevaluatecode">prepared to evaluate ECMAScript code</emu-xref> at the time of _job_'s invocation.</li>
<li>Let _scriptOrModule_ be GetActiveScriptOrModule() at the time HostEnqueuePromiseJob is invoked. If _realm_ is not *null*, each time _job_ is invoked the implementation must perform implementation-defined steps such that _scriptOrModule_ is the <emu-xref href="#job-activescriptormodule">active script or module</emu-xref> at the time of _job_'s invocation.</li>
<li>Jobs must run in the same order as the HostEnqueuePromiseJob invocations that scheduled them.</li>
</ul>

Expand Down