From 36fd4f01e4bebf9b7dfe00b7bfbded8834c4739b Mon Sep 17 00:00:00 2001
From: Julian Descottes <jdescottes@mozilla.com>
Date: Tue, 2 Feb 2021 19:08:22 +0000
Subject: [PATCH] Bug 1686950 - [devtools] RDM should stop watching resources
 and targets after performing cleanup r=nchevobbe

Depends on D103325

When we stop watching for resources, if there are no other watchers currently in activity, we will unregister the JSWindowActors, with following stack:
```
unregisterJSWindowActor@resource://devtools/server/actors/watcher/WatcherRegistry.jsm:344:17
maybeUnregisteringJSWindowActor@resource://devtools/server/actors/watcher/WatcherRegistry.jsm:280:7
unwatchTargets@resource://devtools/server/actors/watcher.js:199:21
handler@resource://devtools/shared/protocol/Actor.js:172:37
onPacket@resource://devtools/server/devtools-server-connection.js:379:58
send/<@resource://devtools/shared/transport/local-transport.js:68:25
exports.makeInfallible/<@resource://devtools/shared/ThreadSafeDevToolsUtils.js:103:22
DevToolsUtils.executeSoon*exports.executeSoon@resource://devtools/shared/DevToolsUtils.js:54:21
send@resource://devtools/shared/transport/local-transport.js:56:21
send@resource://devtools/shared/protocol/Front.js:272:30
generateRequestMethods/</frontProto[name]@resource://devtools/shared/protocol/Front/FrontClassWithSpec.js:42:14
stopListening@resource://devtools/shared/resources/target-list.js:363:29
destroy@resource://devtools/shared/resources/target-list.js:612:10
```

This will lead to destroy all the currently created JSWindowActors, which will also destroy the corresponding target actors.
However RDM will still try to perform some cleanups on the current target after destroying the target-list. These calls will fail as soon as RDM uses a JSWindowActor based target.
This will only start happening in Bug 1644397, but then it will make the test browser_tab_remoteness_change_fission_switch_target.js fail on shutdown.

Differential Revision: https://phabricator.services.mozilla.com/D103326
---
 devtools/client/responsive/ui.js | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/devtools/client/responsive/ui.js b/devtools/client/responsive/ui.js
index 3249d2233d9f..d9876a0140cb 100644
--- a/devtools/client/responsive/ui.js
+++ b/devtools/client/responsive/ui.js
@@ -295,18 +295,6 @@ class ResponsiveUI {
       // Resseting the throtting needs to be done before the
       // network events watching is stopped.
       await this.updateNetworkThrottling();
-
-      this.targetList.unwatchTargets(
-        [this.targetList.TYPES.FRAME],
-        this.onTargetAvailable
-      );
-
-      this.resourceWatcher.unwatchResources(
-        [this.resourceWatcher.TYPES.NETWORK_EVENT],
-        { onAvailable: this.onNetworkResourceAvailable }
-      );
-
-      this.targetList.destroy();
     }
 
     this.tab.removeEventListener("TabClose", this);
@@ -344,6 +332,22 @@ class ResponsiveUI {
       if (reloadNeeded && currentTarget) {
         await currentTarget.reload();
       }
+
+      // Unwatch targets & resources as the last step. If we are not waching for
+      // any resource & target anymore, the JSWindowActors will be unregistered
+      // which will trigger an early destruction of the RDM target, before we
+      // could finalize the cleanup.
+      this.targetList.unwatchTargets(
+        [this.targetList.TYPES.FRAME],
+        this.onTargetAvailable
+      );
+
+      this.resourceWatcher.unwatchResources(
+        [this.resourceWatcher.TYPES.NETWORK_EVENT],
+        { onAvailable: this.onNetworkResourceAvailable }
+      );
+
+      this.targetList.destroy();
     }
 
     // Show the browser UI now.