extensionSystem: Rebase the extension order list to help prevent conflicts

When two extensions monkey-patch the same area, enable() and disable() may
behave badly and completely wreck things. To solve this, when disabling
an extension, "rebase" the extension list so that monkey patches should be
added and removed in order.

https://bugzilla.gnome.org/show_bug.cgi?id=661815

diff --git a/js/ui/extensionSystem.js b/js/ui/extensionSystem.js
index c30da01cc8ecb0983c683e812bcee52c09451828..95c3a29ed7ff967963cb6d37729d2d11edc2b603 100644 (file)
--- a/js/ui/extensionSystem.js
+++ b/js/ui/extensionSystem.js
@@ -64,6 +64,8 @@ const extensions = {};
 const extensionStateObjs = {};
 // Maps uuid -> [GFile to the extension directory, Extension type]
 const extensionDirs = {};
+// Contains the order that extensions were enabled in.
+const extensionOrder = [];
 
 // Arrays of uuids
 var enabledExtensions;
@@ -215,6 +217,27 @@ function disableExtension(uuid) {
 
     let extensionState = extensionStateObjs[uuid];
 
+    // "Rebase" the extension order by disabling and then enabling extensions
+    // in order to help prevent conflicts.
+
+    // Example:
+    //   order = [A, B, C, D, E]
+    //   user disables C
+    //   this should: disable E, disable D, disable C, enable D, enable E
+
+    let orderIdx = extensionOrder.indexOf(uuid);
+    let order = extensionOrder.slice(orderIdx + 1);
+    let orderReversed = order.slice().reverse();
+
+    for (let i = 0; i < orderReversed.length; i++) {
+        let uuid = orderReversed[i];
+        try {
+            extensionStateObjs[uuid].disable();
+        } catch(e) {
+            logExtensionError(uuid, e.toString());
+        }
+    }
+
     try {
         extensionState.disable();
     } catch(e) {
@@ -222,6 +245,15 @@ function disableExtension(uuid) {
         return;
     }
 
+    for (let i = 0; i < order.length; i++) {
+        let uuid = order[i];
+        try {
+            extensionStateObjs[uuid].enable();
+        } catch(e) {
+            logExtensionError(uuid, e.toString());
+        }
+    }
+
     meta.state = ExtensionState.DISABLED;
     _signals.emit('extension-state-changed', meta);
 }
@@ -241,6 +273,8 @@ function enableExtension(uuid) {
 
     let extensionState = extensionStateObjs[uuid];
 
+    extensionOrder.push(uuid);
+
     try {
         extensionState.enable();
     } catch(e) {