Bug 1676808 - [devtools] Expose WatcherFront via the TargetList instead of ResourceWatcher. r=jdescottes

Differential Revision: https://phabricator.services.mozilla.com/D96804

devtools/client/fronts/descriptors/process.js

@@ -99,15 +99,6 @@ class ProcessDescriptorFront extends FrontClassWithSpec(processDescriptorSpec) {
     return this._targetFrontPromise;
   }
 
-  getCachedWatcher() {
-    for (const child of this.poolChildren()) {
-      if (child.typeName == "watcher") {
-        return child;
-      }
-    }
-    return null;
-  }
-
   destroy() {
     if (this._processTargetFront) {
       this._processTargetFront.destroy();

devtools/client/fronts/descriptors/tab.js

@@ -210,15 +210,6 @@ class TabDescriptorFront extends FrontClassWithSpec(tabDescriptorSpec) {
     return this._targetFrontPromise;
   }
 
-  getCachedWatcher() {
-    for (const child of this.poolChildren()) {
-      if (child.typeName == "watcher") {
-        return child;
-      }
-    }
-    return null;
-  }
-
   /**
    * Handle tabs events.
    */

devtools/shared/resources/resource-watcher.js

@@ -22,7 +22,6 @@ class ResourceWatcher {
 
   constructor(targetList) {
     this.targetList = targetList;
-    this.descriptorFront = targetList.descriptorFront;
 
     this._onTargetAvailable = this._onTargetAvailable.bind(this);
     this._onTargetDestroyed = this._onTargetDestroyed.bind(this);
@@ -45,6 +44,10 @@ class ResourceWatcher {
     this._throttledNotifyWatchers = throttle(this._notifyWatchers, 100);
   }
 
+  get watcher() {
+    return this.targetList.watcher;
+  }
+
   /**
    * Return all specified resources cached in this watcher.
    *
@@ -103,27 +106,23 @@ class ResourceWatcher {
       );
     }
 
-    // Cache the Watcher once for all, the first time we call `watch()`.
-    // This `watcher` attribute may be then used in any function of the ResourceWatcher after this.
-    if (!this.watcher) {
-      const supportsWatcher = this.descriptorFront?.traits?.watcher;
-      if (supportsWatcher) {
-        this.watcher = await this.descriptorFront.getWatcher();
-        // Resources watched from the parent process will be emitted on the Watcher Actor.
-        // So that we also have to listen for this event on it, in addition to all targets.
-        this.watcher.on(
-          "resource-available-form",
-          this._onResourceAvailable.bind(this, { watcherFront: this.watcher })
-        );
-        this.watcher.on(
-          "resource-updated-form",
-          this._onResourceUpdated.bind(this, { watcherFront: this.watcher })
-        );
-        this.watcher.on(
-          "resource-destroyed-form",
-          this._onResourceDestroyed.bind(this, { watcherFront: this.watcher })
-        );
-      }
+    // Bug 1675763: Watcher actor is not available in all situations yet.
+    if (!this._listenerRegistered && this.watcher) {
+      this._listenerRegistered = true;
+      // Resources watched from the parent process will be emitted on the Watcher Actor.
+      // So that we also have to listen for this event on it, in addition to all targets.
+      this.watcher.on(
+        "resource-available-form",
+        this._onResourceAvailable.bind(this, { watcherFront: this.watcher })
+      );
+      this.watcher.on(
+        "resource-updated-form",
+        this._onResourceUpdated.bind(this, { watcherFront: this.watcher })
+      );
+      this.watcher.on(
+        "resource-destroyed-form",
+        this._onResourceDestroyed.bind(this, { watcherFront: this.watcher })
+      );
     }
 
     // First ensuring enabling listening to targets.

devtools/shared/resources/target-list.js

@@ -229,6 +229,10 @@ class TargetList extends EventEmitter {
     return this._listenersStarted.has(type);
   }
 
+  hasTargetWatcherSupport(type) {
+    return !!this.watcher?.traits[type];
+  }
+
   /**
    * Start listening for targets from the server
    *
@@ -245,6 +249,16 @@ class TargetList extends EventEmitter {
    *        but still register listeners set via Legacy Listeners.
    */
   async startListening({ onlyLegacy = false } = {}) {
+    // Cache the Watcher once for all, the first time we call `startListening()`.
+    // This `watcher` attribute may be then used in any function in TargetList or ResourceWatcher after this.
+    if (!this.watcher) {
+      // Bug 1675763: Watcher actor is not available in all situations yet.
+      const supportsWatcher = this.descriptorFront?.traits?.watcher;
+      if (supportsWatcher) {
+        this.watcher = await this.descriptorFront.getWatcher();
+      }
+    }
+
     let types = [];
     if (this.targetFront.isParentProcess) {
       const fissionBrowserToolboxEnabled = Services.prefs.getBoolPref(
@@ -283,24 +297,20 @@ class TargetList extends EventEmitter {
       this._setListening(type, true);
 
       // Starting with FF77, we support frames watching via watchTargets for Tab and Process descriptors
-      const supportsWatcher = this.descriptorFront?.traits?.watcher;
-      if (supportsWatcher) {
-        const watcher = await this.descriptorFront.getWatcher();
-        if (watcher.traits[type]) {
-          // When we switch to a new top level target, we don't have to stop and restart
-          // Watcher listener as it is independant from the top level target.
-          // This isn't the case for some Legacy Listeners, which fetch targets from the top level target
-          if (onlyLegacy) {
-            continue;
-          }
-          if (!this._startedListeningToWatcher) {
-            this._startedListeningToWatcher = true;
-            watcher.on("target-available", this._onTargetAvailable);
-            watcher.on("target-destroyed", this._onTargetDestroyed);
-          }
-          await watcher.watchTargets(type);
+      if (this.hasTargetWatcherSupport(type)) {
+        // When we switch to a new top level target, we don't have to stop and restart
+        // Watcher listener as it is independant from the top level target.
+        // This isn't the case for some Legacy Listeners, which fetch targets from the top level target
+        if (onlyLegacy) {
           continue;
         }
+        if (!this._startedListeningToWatcher) {
+          this._startedListeningToWatcher = true;
+          this.watcher.on("target-available", this._onTargetAvailable);
+          this.watcher.on("target-destroyed", this._onTargetDestroyed);
+        }
+        await this.watcher.watchTargets(type);
+        continue;
       }
       if (this.legacyImplementation[type]) {
         await this.legacyImplementation[type].listen();
@@ -326,18 +336,14 @@ class TargetList extends EventEmitter {
       this._setListening(type, false);
 
       // Starting with FF77, we support frames watching via watchTargets for Tab and Process descriptors
-      const supportsWatcher = this.descriptorFront?.traits?.watcher;
-      if (supportsWatcher) {
-        const watcher = this.descriptorFront.getCachedWatcher();
-        if (watcher && watcher.traits[type]) {
-          // When we switch to a new top level target, we don't have to stop and restart
-          // Watcher listener as it is independant from the top level target.
-          // This isn't the case for some Legacy Listeners, which fetch targets from the top level target
-          if (!onlyLegacy) {
-            watcher.unwatchTargets(type);
-          }
-          continue;
+      if (this.hasTargetWatcherSupport(type)) {
+        // When we switch to a new top level target, we don't have to stop and restart
+        // Watcher listener as it is independant from the top level target.
+        // This isn't the case for some Legacy Listeners, which fetch targets from the top level target
+        if (!onlyLegacy) {
+          this.watcher.unwatchTargets(type);
         }
+        continue;
       }
       if (this.legacyImplementation[type]) {
         this.legacyImplementation[type].unlisten();