Overhaul document unloading/destruction/aborting

As noted in #9148, the way in which destroy calls abort, and unload calls destroy, is not sound when most of these algorithms act on the entire tree. Instead, we need to split these algorithms into single-document base variants, which call each other, and whole-tree "document and its descendant" variants, which proceed carefully.

The whole-tree variants in particular need to take care with how they queue tasks. We cannot fire events (like unload for unloading, or readystatechange for aborting) inside of inactive documents, so we need to delay making a document inactive until its children have been processed. (The related issue #9869 around reloading is not yet solved, however, since that is a special case where the same session history entry is reused and thus making documents inactive is harder to avoid.)

Closes #9148.

source

@@ -95068,7 +95068,7 @@ interface <dfn interface>BeforeUnloadEvent</dfn> : <span>Event</span> {
    <li><p><span>Inform the navigation API about child navigable destruction</span> given
    <var>navigable</var>.</p></li>
 
-   <li><p><span data-x="destroy a document">Destroy</span> <var>navigable</var>'s <span
+   <li><p><span>Destroy a document and its descendants</span> given <var>navigable</var>'s <span
    data-x="nav-document">active document</span>.</p></li>
 
    <li><p>Let <var>parentDocState</var> be <var>container</var>'s <span>node navigable</span>'s
@@ -95110,8 +95110,8 @@ interface <dfn interface>BeforeUnloadEvent</dfn> : <span>Event</span> {
      <li><p>Let <var>document</var> be <var>historyEntry</var>'s <span
      data-x="she-document">document</span>.</p></li>
 
-     <li><p>If <var>document</var> is not null, then <span data-x="destroy a
-     document">destroy</span> <var>document</var>.</p></li>
+     <li><p>If <var>document</var> is not null, then <span>destroy a document and its
+     descendants</span> given <var>document</var>.</p></li>
     </ol>
    </li>
 
@@ -95139,12 +95139,18 @@ interface <dfn interface>BeforeUnloadEvent</dfn> : <span>Event</span> {
    <li><p>If the result of <span>checking if unloading is canceled</span> for <var>toUnload</var> is
    true, then return.</p></li>
 
-   <li><p><span data-x="unload a document">Unload</span> the <span data-x="nav-document">active
-   documents</span> of each of <var>toUnload</var>.  <span class="XXX" data-x="">In what
-   order?</span></p></li>
+   <li>
+    <p><span data-x="tn-append-session-history-traversal-steps">Append the following session
+    history traversal steps</span> to <var>traversable</var>:</p>
 
-   <li><p><span data-x="destroy a top-level traversable">Destroy</span>
-   <var>traversable</var>.</p></li>
+    <ol>
+     <li><p>Let <var>afterAllUnloads</var> be an algorithm step which <p><span data-x="destroy a
+     top-level traversable">destroys</span> <var>traversable</var>.</p></li>
+
+     <li><p><span>Unload a document and its descendants</span> given <var>traversable</var>'s <span
+     data-x="nav-document">active document</span>, null, and <var>afterAllUnloads</var>.</p></li>
+    </ol>
+   </li>
   </ol>
 
 
@@ -96363,7 +96369,7 @@ interface <dfn interface>BeforeUnloadEvent</dfn> : <span>Event</span> {
    name</dfn> string, initially the empty string.</p></li>
   </ul>
 
-  <p>User agents may <span data-x="destroy a Document">destroy</span> the <span
+  <p>User agents may <span>destroy a document and its descendants</span> given the <span
   data-x="document-state-document">documents</span> of <span data-x="document state">document
   states</span> with non-null <span data-x="document-state-document">documents</span>, as long as
   the <code>Document</code> is not <span>fully active</span>.</p>
@@ -97446,7 +97452,7 @@ location.href = '#foo';</code></pre>
 
      <li><p><span>Queue a global task</span> on the <span>navigation and traversal task
      source</span> given <var>navigable</var>'s <span data-x="nav-window">active window</span> to
-     <span data-x="abort a document">abort</span> <var>navigable</var>'s <span
+     <span>abort a document and its descendants</span> given <var>navigable</var>'s <span
      data-x="nav-document">active document</span>.</p></li>
 
      <li id="navigation-create-document-state">
@@ -100511,36 +100517,24 @@ location.href = '#foo';</code></pre>
      <var>targetStep</var>.</p></li>
 
      <li>
-      <p><span>Queue a global task</span> on the <span>navigation and traversal task source</span>
-      given <var>navigable</var>'s <span data-x="nav-window">active window</span> to run the
-      steps:</p>
+      <p>If <var>changingNavigableContinuation</var>'s <span
+      data-x="changing-nav-continuation-update-only">update-only</span> is false, and
+      <var>targetEntry</var>'s <span data-x="she-document">document</span> does not equal
+      <var>displayedDocument</var>, then <span>unload a document and its descendants</span> given
+      <var>displayedDocument</var>, <var>targetEntry</var>'s <span
+      data-x="she-document">document</span>, and <var>afterPotentialUnloads</var>.</p>
 
-      <ol>
-       <li>
-        <p>If <var>changingNavigableContinuation</var>'s <span
-        data-x="changing-nav-continuation-update-only">update-only</span> is false, then:</p>
+      <p>Otherwise, <span>queue a global task</span> on the <span>navigation and traversal task
+      source</span> given <var>navigable</var>'s <span data-x="nav-window">active window</span> to
+      perform <var>afterPotentialUnloads</var>.</p>
 
-        <ol>
-         <li>
-          <p>If <var>targetEntry</var>'s <span data-x="she-document">document</span> does not equal
-          <var>displayedDocument</var>, then:</p>
+      <p>In both cases, let <var>afterPotentialUnloads</var> be the following steps:</p>
 
-          <ol>
-           <li><p><span data-x="unload a document">Unload</span> <var>displayedDocument</var> given
-           <var>targetEntry</var>'s <span data-x="she-document">document</span>.</p></li>
-
-           <li><p>For each <var>childNavigable</var> of <var>displayedDocument</var>'s
-           <span>descendant navigables</span>, <span>queue a global task</span> on the
-           <span>navigation and traversal task source</span> given <var>childNavigable</var>'s
-           <span data-x="nav-window">active window</span> to <span data-x="unload a
-           document">unload</span> <var>childNavigable</var>'s <span data-x="nav-document">active
-           document</span>.</p></li>
-          </ol>
-
-         <li><p><span>Activate history entry</span> <var>targetEntry</var> for
-         <var>navigable</var>.</p></li>
-        </ol>
-       </li>
+      <ol>
+       <li><p>If <var>changingNavigableContinuation</var>'s <span
+       data-x="changing-nav-continuation-update-only">update-only</span> is false, then
+       <span>activate history entry</span> <var>targetEntry</var> for
+       <var>navigable</var>.</p></li>
 
        <li><p>Let <var>updateDocument</var> be an algorithm step which performs <span>update
        document for history step application</span> given <var>targetEntry</var>'s <span
@@ -102188,7 +102182,8 @@ new PaymentRequest(&hellip;); // Allowed to use
 
   <ol>
    <li><p><span>Assert</span>: this is running as part of a <span data-x="concept-task">task</span>
-   queued on <var>oldDocument</var>'s <span>event loop</span>.</p></li>
+   queued on <var>oldDocument</var>'s <span>relevant agent</span>'s <span
+   data-x="concept-agent-event-loop">event loop</span>.</p></li>
 
    <li><p>Let <var>unloadTimingInfo</var> be a new <span>document unload timing
    info</span>.</p></li>
@@ -102295,6 +102290,52 @@ new PaymentRequest(&hellip;); // Allowed to use
    <var>unloadTimingInfo</var>.</p></li>
   </ol>
 
+  <p>To <dfn>unload a document and its descendants</dfn>, given a <code>Document</code>
+  <var>document</var>, an optional <code>Document</code>-or-null <var>newDocument</var> (default
+  null), and an optional set of steps <var>afterAllUnloads</var>:</p>
+
+  <ol>
+   <li><p><span>Assert</span>: this is running within <var>document</var>'s <span>node
+   navigable</span>'s <span data-x="nav-traversable">traversable navigable</span>'s <span
+   data-x="tn-session-history-traversal-queue">session history traversal queue</span>.</p></li>
+
+   <li><p>Let <var>childNavigables</var> be <var>document</var>'s <span data-x="child
+   navigable">child navigables</span>.</p></li>
+
+   <li><p>Let <var>numberUnloaded</var> be 0.</p></li>
+
+   <li>
+    <p><span data-x="list iterate">For each</span> <var>childNavigable</var> of
+    <var>childNavigable</var>'s <span class="XXX" data-x="">in what order?</span>, <span>queue a
+    global task</span> on the <span>navigation and traversal task source</span> given
+    <var>childNavigable</var>'s <span data-x="nav-window">active window</span> to perform the
+    following steps:</p>
+
+    <ol>
+     <li><p><span data-x="unload a document">Unload</span> <var>childNavigable</var>'s <span
+     data-x="nav-document">active document</span>.</p></li>
+
+     <li><p>Increment <var>numberUnloaded</var>.</p></li>
+    </ol>
+   </li>
+
+   <li><p>Wait until <var>numberUnloaded</var> equals <var>childNavigable</var>'s <span
+   data-x="list size">size</span>.</p></li>
+
+   <li>
+    <p><span>Queue a global task</span> on the <span>navigation and traversal task source</span>
+    given <var>document</var>'s <span>relevant global object</span> to perform the following
+    steps:</p>
+
+    <ol>
+     <li><p><span data-x="unload a document">Unload</span> <var>document</var>, passing along
+     <var>newDocument</var> if it is not null.</p></li>
+
+     <li><p>If <var>afterAllUnloads</var> was given, then run it.</p></li>
+    </ol>
+   </li>
+  </ol>
+
   <p>This specification defines the following <dfn export>unloading document cleanup steps</dfn>.
   Other specifications can define more. Given a <code>Document</code> <var>document</var>:</p>
 
@@ -102354,18 +102395,18 @@ new PaymentRequest(&hellip;); // Allowed to use
   <code>Document</code> <var>document</var>:</p>
 
   <ol>
-   <li><p><span data-x="destroy a document">Destroy</span> the <span
-   data-x="nav-document">active documents</span> of each of <var>document</var>'s <span>descendant
-   navigables</span>. <span class="XXX" data-x="">In what order?</span></p></li>
+   <li><p><span>Assert</span>: this is running as part of a <span data-x="concept-task">task</span>
+   queued on <var>document</var>'s <span>relevant agent</span>'s <span
+   data-x="concept-agent-event-loop">event loop</span>.</p></li>
+
+   <li><p><span data-x="abort a document">Abort</span> <var>document</var>.</p></li>
 
    <li><p>Set <var>document</var>'s <i data-x="concept-document-salvageable">salvageable</i> state
    to false.</p></li>
 
    <li><p>Run any <span>unloading document cleanup steps</span> for <var>document</var> that
    are defined by this specification and <span>other applicable specifications</span>.</p></li>
 
-   <li><p><span data-x="abort a document">Abort</span> <var>document</var>.</p></li>
-
    <li><p>Remove any <span data-x="concept-task">tasks</span> whose <span
    data-x="concept-task-document">document</span> is <var>document</var> from any <span>task
    queue</span> (without running those tasks).</p></li>
@@ -102392,22 +102433,51 @@ new PaymentRequest(&hellip;); // Allowed to use
   accessible to script, in the case where we are <span data-x="destroy a child
   navigable">destroying a child navigable</span>.</p>
 
+  <p>To <dfn>destroy a document and its descendants</dfn> given a <code>Document</code>
+  <var>document</var>, perform the following steps <span>in parallel</span>:</p>
+
+  <ol>
+   <li><p>Let <var>childNavigables</var> be <var>document</var>'s <span data-x="child
+   navigable">child navigables</span>.</p></li>
+
+   <li><p>Let <var>numberDestroyed</var> be 0.</p></li>
+
+   <li>
+    <p><span data-x="list iterate">For each</span> <var>childNavigable</var> of
+    <var>childNavigable</var>'s <span class="XXX" data-x="">in what order?</span>, <span>queue a
+    global task</span> on the <span>navigation and traversal task source</span> given
+    <var>childNavigable</var>'s <span data-x="nav-window">active window</span> to perform the
+    following steps:</p>
+
+    <ol>
+     <li><p><span data-x="destroy a document">Destroy</span> <var>childNavigable</var>'s <span
+     data-x="nav-document">active document</span>.</p></li>
+
+     <li><p>Increment <var>numberDestroyed</var>.</p></li>
+    </ol>
+   </li>
+
+   <li><p>Wait until <var>numberDestroyed</var> equals <var>childNavigable</var>'s <span
+   data-x="list size">size</span>.</p></li>
+
+   <li><p><span>Queue a global task</span> on the <span>navigation and traversal task source</span>
+   given <var>document</var>'s <span>relevant global object</span> to <span data-x="destroy a
+   document">destroy</span> <var>document</var>.</p></li>
+  </ol>
+
   <h4>Aborting a document load</h4>
 
   <p>To <dfn data-x="abort a document">abort</dfn> a <code>Document</code> <var>document</var>:</p>
 
   <ol>
-   <li><p><span data-x="abort a document">Abort</span> the <span data-x="nav-document">active
-   documents</span> of each of <var>document</var>'s <span>descendant navigables</span>. <span
-   class="XXX" data-x="">In what order?</span> If this results in any of those <code>Document</code>
-   objects having their <i data-x="concept-document-salvageable">salvageable</i> state set to false,
-   then set <var>document</var>'s <i data-x="concept-document-salvageable">salvageable</i> state to
-   false also.</p></li>
+   <li><p><span>Assert</span>: this is running as part of a <span data-x="concept-task">task</span>
+   queued on <var>document</var>'s <span>relevant agent</span>'s <span
+   data-x="concept-agent-event-loop">event loop</span>.</p></li>
 
    <li><p>Cancel any instances of the <span data-x="concept-fetch">fetch</span> algorithm in the
-   context of <var>document</var>, discarding any <span data-x="concept-task">tasks</span>
-   <span data-x="queue a task">queued</span> for them, and discarding any further data received from
-   the network for them. If this resulted in any instances of the <span
+   context of <var>document</var>, discarding any <span data-x="concept-task">tasks</span> <span
+   data-x="queue a task">queued</span> for them, and discarding any further data received from the
+   network for them. If this resulted in any instances of the <span
    data-x="concept-fetch">fetch</span> algorithm being canceled or any <span data-x="queue a
    task">queued</span> <span data-x="concept-task">tasks</span> or any network data getting
    discarded, then set <var>document</var>'s <i
@@ -102440,12 +102510,44 @@ new PaymentRequest(&hellip;); // Allowed to use
 
      <li><p><span data-x="abort a parser">Abort that parser</span>.</p></li>
 
-     <li><p>Set <var>document</var>'s <i data-x="concept-document-salvageable">salvageable</i> state
-     to false.</p></li>
+     <li><p>Set <var>document</var>'s <i data-x="concept-document-salvageable">salvageable</i> to
+     false.</p></li>
     </ol>
    </li>
   </ol>
 
+  <p>To <dfn>abort a document and its descendants</dfn> given a <code>Document</code>
+  <var>document</var>:</p>
+
+  <ol>
+   <li><p><span>Assert</span>: this is running as part of a <span data-x="concept-task">task</span>
+   queued on <var>document</var>'s <span>relevant agent</span>'s <span
+   data-x="concept-agent-event-loop">event loop</span>.</p></li>
+
+   <li><p>Let <var>descendantNavigables</var> be <var>document</var>'s <span>descendant
+   navigables</span>.</p></li>
+
+   <li>
+    <p><span data-x="list iterate">For each</span> <var>descendantNavigable</var> of
+    <var>descendantNavigables</var> <span class="XXX" data-x="">in what order?</span>, <span>queue
+    a global task</span> on the <span>navigation and traversal task source</span> given
+    <var>descendantNavigable</var>'s <span data-x="nav-window">active window</span> to perform the
+    following steps:</p>
+
+    <ol>
+     <li><p><span data-x="abort a document">Abort</span> <var>descendantNavigable</var>'s <span
+     data-x="nav-document">active document</span>.</p></li>
+
+     <li><p>If <var>descendantNavigable</var>'s <span data-x="nav-document">active
+     document</span>'s <i data-x="concept-document-salvageable">salvageable</i> is false, then set
+     <var>document</var>'s <i data-x="concept-document-salvageable">salvageable</i> to
+     false.</p></li>
+    </ol>
+   </li>
+
+   <li><p><span data-x="abort a document">Abort</span> <var>document</var>.</p></li>
+  </ol>
+
   <p id="stop-document-loading">To <dfn data-x="nav-stop">stop loading</dfn> a
   <span>navigable</span> <var>navigable</var>:</p>
 
@@ -102463,7 +102565,7 @@ new PaymentRequest(&hellip;); // Allowed to use
     navigation</span> will cause further work to be abandoned.</p>
    </li>
 
-   <li><p><span data-x="abort a document">Abort</span> <var>document</var>.</p></li>
+   <li><p><span>Abort a document and its descendants</span> given <var>document</var>.</p></li>
   </ol>
 
   <p class="XXX">Through their <a href="#nav-traversal-ui">user interface</a>, user agents also