Normative: Flush Job Queue between module imports

Closes tc39#47, tc39#43, tc39#48, tc39#50

spec.html

@@ -370,11 +370,9 @@ <h1>InnerModuleEvaluation( _module_, _stack_, _index_ )</h1>
           1. If _requiredModule_.[[Status]] is `"evaluating"`, then
             1. Assert: _requiredModule_ is a Source Text Module Record.
             1. Set _module_.[[DFSAncestorIndex]] to min(_module_.[[DFSAncestorIndex]], _requiredModule_.[[DFSAncestorIndex]]).
-            1. <ins>Let _stackErrorCapability_ be ! NewPromiseCapability(%Promise%).</ins>
-            1. <ins>Perform ! PerformPromiseThen(_requiredModule_.[[ExecPromise]], *undefined*, _stackErrorCapability_.[[Reject]]).</ins>
-            1. <ins>Add _stackErrorCapability_ to the list _dependencyExecPromises_.</ins>
         1. <del>Perform ? ModuleExecution(_module_).</del>
         1. <ins>Perform ! ExecuteModuleWhenImportsReady(_module_, _dependencyExecPromises_, _evalCapability_).</ins>
+        1. <ins>Perform ! FlushJobs().</ins>
         1. Assert: _module_ occurs exactly once in _stack_.
         1. Assert: _module_.[[DFSAncestorIndex]] is less than or equal to _module_.[[DFSIndex]].
         1. If _module_.[[DFSAncestorIndex]] equals _module_.[[DFSIndex]], then
@@ -384,6 +382,7 @@ <h1>InnerModuleEvaluation( _module_, _stack_, _index_ )</h1>
             1. Remove the last element of _stack_.
             1. Set _requiredModule_.[[Status]] to `"evaluated"`.
             1. If _requiredModule_ and _module_ are the same Module Record, set _done_ to *true*.
+            1. <ins>Otherwise, set _requiredModule_.[[ExecPromise]] to _module_.[[ExecPromise]].</ins>
         1. Return _index_.
       </emu-alg>
       <emu-note>
@@ -508,6 +507,20 @@ <h1>Runtime Semantics: TopLevelModuleEvaluationJob ( _sourceText_, _hostDefined_
       <p>An implementation may parse a _sourceText_ as a |Module|, analyse it for Early Error conditions, and instantiate it prior to the execution of the TopLevelModuleEvaluationJob for that _sourceText_. An implementation may also resolve, pre-parse and pre-analyse, and pre-instantiate module dependencies of _sourceText_. However, the reporting of any errors detected by these actions must be deferred until the TopLevelModuleEvaluationJob is actually executed.</p>
     </emu-note>
   </emu-clause>
+
+  <emu-clause id="sec-flushjobs" aoid="FlushJobs">
+    <h1>FlushJobs ( )</h1>
+    <emu-alg>
+      1. Assert: There is no running execution context.
+      1. Yield control to the RunJobs algorithm.
+      1. When RunJobs has no more jobs to run, return from this algorithm.
+    </emu-alg>
+    <emu-note type=editor>
+      <p>This algorithm completes asynchronously, but is to be used synchronously within a larger ECMAScript algorithm. For this reason, it may only be called when there is no running execution context.</p>
+      <p>HTML and ECMAScript have different notions of how the Job Queue works, with HTML employing a willful violation to describe the layering; see <a href="https://html.spec.whatwg.org/#integration-with-the-javascript-job-queue">Integration with the JavaScript job queue</a> for details.See <a href="https://github.com/tc39/ecma262/pull/735">#735</a> for one approach to improving the layering. Until some kind of fix in this area occurs, this proposal sticks with the "willful violation" layering approach.</p>
+      <p>In the HTML context, the FlushJobs() algorithm would be replaced, via a willful violation, with the <a href="https://html.spec.whatwg.org/#perform-a-microtask-checkpoint">perform a microtask checkpoint</a> algorithm</p>
+    </emu-note>
+  </emu-clause>
 </emu-clause>
 
 <emu-clause id="sec-modules">