extensionSystem: Add canChange property to extensions

Whether or not an extension can be enabled/disabled depends on various
factors: Whether the extension is in error state, whether user extensions
are disabled and whether the underlying GSettings keys are writable.

This is complex enough to share the logic, so add it to the extension
properties that are exposed over D-Bus.

https://bugzilla.gnome.org/show_bug.cgi?id=789852

js/misc/extensionUtils.js

@@ -30,7 +30,7 @@ var ExtensionState = {
     UNINSTALLED: 99
 };
 
-const SERIALIZED_PROPERTIES = ['type', 'state', 'path', 'error', 'hasPrefs'];
+const SERIALIZED_PROPERTIES = ['type', 'state', 'path', 'error', 'hasPrefs', 'canChange'];
 
 // Maps uuid -> metadata object
 var extensions = {};
@@ -219,6 +219,7 @@ function createExtensionObject(uuid, dir, type) {
     extension.path = dir.get_path();
     extension.error = '';
     extension.hasPrefs = dir.get_child('prefs.js').query_exists(null);
+    extension.canChange = false;
 
     extensions[uuid] = extension;
 

js/ui/extensionSystem.js

@@ -189,6 +189,7 @@ var ExtensionManager = class {
             }
         }
 
+        this._updateCanChange(extension);
         this.emit('extension-state-changed', extension);
     }
 
@@ -267,12 +268,28 @@ var ExtensionManager = class {
         return true;
     }
 
-    _getEnabledExtensions() {
-        let extensions;
+    _getModeExtensions() {
         if (Array.isArray(Main.sessionMode.enabledExtensions))
-            extensions = Main.sessionMode.enabledExtensions;
-        else
-            extensions = [];
+            return Main.sessionMode.enabledExtensions;
+        return [];
+    }
+
+    _updateCanChange(extension) {
+        let hasError =
+            extension.state == ExtensionState.ERROR ||
+            extension.state == ExtensionState.OUT_OF_DATE;
+
+        let isMode = this._getModeExtensions().includes(extension.uuid);
+        let modeOnly = global.settings.get_boolean(DISABLE_USER_EXTENSIONS_KEY);
+
+        extension.canChange =
+            !hasError &&
+            global.settings.is_writable(ENABLED_EXTENSIONS_KEY) &&
+            (isMode || !modeOnly);
+    }
+
+    _getEnabledExtensions() {
+        let extensions = this._getModeExtensions();
 
         if (global.settings.get_boolean(DISABLE_USER_EXTENSIONS_KEY))
             return extensions;
@@ -280,6 +297,11 @@ var ExtensionManager = class {
         return extensions.concat(global.settings.get_strv(ENABLED_EXTENSIONS_KEY));
     }
 
+    _onUserExtensionsEnabledChanged() {
+        this._onEnabledExtensionsChanged();
+        this._onSettingsWritableChanged();
+    }
+
     _onEnabledExtensionsChanged() {
         let newEnabledExtensions = this._getEnabledExtensions();
 
@@ -305,6 +327,14 @@ var ExtensionManager = class {
         this._enabledExtensions = newEnabledExtensions;
     }
 
+    _onSettingsWritableChanged() {
+        for (let uuid in ExtensionUtils.extensions) {
+            let extension = ExtensionUtils.extensions[uuid];
+            this._updateCanChange(extension);
+            this.emit('extension-state-changed', extension);
+        }
+    }
+
     _onVersionValidationChanged() {
         // we want to reload all extensions, but only enable
         // extensions when allowed by the sessionMode, so
@@ -325,9 +355,11 @@ var ExtensionManager = class {
         global.settings.connect(`changed::${ENABLED_EXTENSIONS_KEY}`,
             this._onEnabledExtensionsChanged.bind(this));
         global.settings.connect(`changed::${DISABLE_USER_EXTENSIONS_KEY}`,
-            this._onEnabledExtensionsChanged.bind(this));
+            this._onUserExtensionsEnabledChanged.bind(this));
         global.settings.connect(`changed::${EXTENSION_DISABLE_VERSION_CHECK_KEY}`,
             this._onVersionValidationChanged.bind(this));
+        global.settings.connect(`writable-changed::${ENABLED_EXTENSIONS_KEY}`,
+            this._onSettingsWritableChanged.bind(this));
 
         this._enabledExtensions = this._getEnabledExtensions();