Fix create function app when workspace items are selected (#3732)

Author: alexweininger

src/commands/createFunctionApp/createFunctionApp.ts

@@ -10,6 +10,16 @@ import { SlotTreeItem } from '../../tree/SlotTreeItem';
 import { ICreateFunctionAppContext, SubscriptionTreeItem } from '../../tree/SubscriptionTreeItem';
 import { ISiteCreatedOptions } from './showSiteCreated';
 
+function isSubscription(item?: AzExtParentTreeItem): boolean {
+    try {
+        // Accessing item.subscription throws an error for some workspace items
+        // see https://github.com/microsoft/vscode-azurefunctions/issues/3731
+        return !!item && !!item.subscription;
+    } catch {
+        return false;
+    }
+}
+
 export async function createFunctionApp(context: IActionContext & Partial<ICreateFunctionAppContext>, subscription?: AzExtParentTreeItem | string, nodesOrNewResourceGroupName?: string | (string | AzExtParentTreeItem)[]): Promise<string> {
     const newResourceGroupName = Array.isArray(nodesOrNewResourceGroupName) ? undefined : nodesOrNewResourceGroupName;
     let node: AzExtParentTreeItem | undefined;
@@ -18,7 +28,7 @@ export async function createFunctionApp(context: IActionContext & Partial<ICreat
         if (!node) {
             throw new Error(localize('noMatchingSubscription', 'Failed to find a subscription matching id "{0}".', subscription));
         }
-    } else if (!subscription) {
+    } else if (!isSubscription(subscription)) {
         node = await ext.rgApi.appResourceTree.showTreeItemPicker<AzExtParentTreeItem>(SubscriptionTreeItem.contextValue, context);
     } else {
         node = subscription;