Show error message when running query on empty list

Author: norascheuch

extensions/ql-vscode/src/remote-queries/repository-selection.ts

@@ -45,9 +45,17 @@ export async function getRepositorySelection(
         case DbItemKind.RemoteSystemDefinedList:
           return { repositoryLists: [selectedDbItem.listName] };
         case DbItemKind.RemoteUserDefinedList:
-          return {
-            repositories: selectedDbItem.repos.map((repo) => repo.repoFullName),
-          };
+          if (selectedDbItem.repos.length === 0) {
+            throw new Error(
+              "The selected repository list is empty. Please add repositories to it before running a query on it.",
+            );
+          } else {
+            return {
+              repositories: selectedDbItem.repos.map(
+                (repo) => repo.repoFullName,
+              ),
+            };
+          }
         case DbItemKind.RemoteOwner:
           return { owners: [selectedDbItem.ownerName] };
         case DbItemKind.RemoteRepo:

extensions/ql-vscode/src/vscode-tests/no-workspace/remote-queries/repository-selection.test.ts

@@ -33,6 +33,19 @@ describe("repository selection", () => {
       );
     });
 
+    it("should return throw error when empt remote user defined list is selected", async () => {
+      const dbManager = setUpDbManager({
+        kind: DbItemKind.RemoteUserDefinedList,
+        repos: [],
+      } as any as DbItem);
+
+      await expect(getRepositorySelection(dbManager)).rejects.toThrow(
+        Error(
+          "The selected repository list is empty. Please add repositories to it before running a query on it.",
+        ),
+      );
+    });
+
     it("should return correct selection when remote system defined list is selected", async () => {
       const dbManager = setUpDbManager({
         kind: DbItemKind.RemoteSystemDefinedList,