1 files changed, 72 insertions, 0 deletions
diff --git a/devtools/shared/commands/target/legacy-target-watchers/legacy-processes-watcher.js b/devtools/shared/commands/target/legacy-target-watchers/legacy-processes-watcher.js
new file mode 100644
index 0000000000..e0c5b18d51
--- /dev/null
+++ b/devtools/shared/commands/target/legacy-target-watchers/legacy-processes-watcher.js
@@ -0,0 +1,72 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+class LegacyProcessesWatcher {
+  constructor(targetCommand, onTargetAvailable, onTargetDestroyed) {
+    this.targetCommand = targetCommand;
+    this.rootFront = targetCommand.rootFront;
+
+    this.onTargetAvailable = onTargetAvailable;
+    this.onTargetDestroyed = onTargetDestroyed;
+
+    this.descriptors = new Set();
+    this._processListChanged = this._processListChanged.bind(this);
+  }
+
+  async _processListChanged() {
+    if (this.targetCommand.isDestroyed()) {
+      return;
+    }
+
+    const processes = await this.rootFront.listProcesses();
+    // Process the new list to detect the ones being destroyed
+    // Force destroyed the descriptor as well as the target
+    for (const descriptor of this.descriptors) {
+      if (!processes.includes(descriptor)) {
+        // Manually call onTargetDestroyed listeners in order to
+        // ensure calling them *before* destroying the descriptor.
+        // Otherwise the descriptor will automatically destroy the target
+        // and may not fire the contentProcessTarget's destroy event.
+        const target = descriptor.getCachedTarget();
+        if (target) {
+          this.onTargetDestroyed(target);
+        }
+
+        descriptor.destroy();
+        this.descriptors.delete(descriptor);
+      }
+    }
+
+    const promises = processes
+      .filter(descriptor => !this.descriptors.has(descriptor))
+      .map(async descriptor => {
+        // Add the new process descriptors to the local list
+        this.descriptors.add(descriptor);
+        const target = await descriptor.getTarget();
+        if (!target) {
+          console.error(
+            "Wasn't able to retrieve the target for",
+            descriptor.actorID
+          );
+          return;
+        }
+        await this.onTargetAvailable(target);
+      });
+
+    await Promise.all(promises);
+  }
+
+  async listen() {
+    this.rootFront.on("processListChanged", this._processListChanged);
+    await this._processListChanged();
+  }
+
+  unlisten() {
+    this.rootFront.off("processListChanged", this._processListChanged);
+  }
+}
+
+module.exports = LegacyProcessesWatcher;