Show error message when running query on empty list

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

@@ -41,20 +41,30 @@ export async function getRepositorySelection(
     if (selectedDbItem) {
       switch (selectedDbItem.kind) {
         case DbItemKind.LocalDatabase || DbItemKind.LocalList:
-          throw new Error("Local databases and lists are not supported yet.");
+          throw new UserCancellationException(
+            "Local databases and lists are not supported yet.",
+          );
         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 UserCancellationException(
+              "The selected repository list is empty. Please add repositories to it before running a variant analysis.",
+            );
+          } else {
+            return {
+              repositories: selectedDbItem.repos.map(
+                (repo) => repo.repoFullName,
+              ),
+            };
+          }
         case DbItemKind.RemoteOwner:
           return { owners: [selectedDbItem.ownerName] };
         case DbItemKind.RemoteRepo:
           return { repositories: [selectedDbItem.repoFullName] };
       }
     } else {
-      throw new Error(
+      throw new UserCancellationException(
         "Please select a remote database to run the query against.",
       );
     }

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

@@ -5,7 +5,11 @@ import { UserCancellationException } from "../../../commandRunner";
 import * as config from "../../../config";
 import { getRepositorySelection } from "../../../remote-queries/repository-selection";
 import { DbManager } from "../../../databases/db-manager";
-import { DbItem, DbItemKind } from "../../../databases/db-item";
+import {
+  DbItem,
+  DbItemKind,
+  RemoteRepoDbItem,
+} from "../../../databases/db-item";
 
 describe("repository selection", () => {
   describe("newQueryRunExperience true", () => {
@@ -19,17 +23,28 @@ describe("repository selection", () => {
       const dbManager = setUpDbManager(undefined);
 
       await expect(getRepositorySelection(dbManager)).rejects.toThrow(
-        Error("Please select a remote database to run the query against."),
+        "Please select a remote database to run the query against.",
       );
     });
 
-    it("should throw error when local database item is selected", async () => {
+    it("should log error when local database item is selected", async () => {
       const dbManager = setUpDbManager({
         kind: DbItemKind.LocalDatabase,
       } as DbItem);
 
       await expect(getRepositorySelection(dbManager)).rejects.toThrow(
-        Error("Local databases and lists are not supported yet."),
+        "Local databases and lists are not supported yet.",
+      );
+    });
+
+    it("should log an error when an empty remote user defined list is selected", async () => {
+      const dbManager = setUpDbManager({
+        kind: DbItemKind.RemoteUserDefinedList,
+        repos: [] as RemoteRepoDbItem[],
+      } as DbItem);
+
+      await expect(getRepositorySelection(dbManager)).rejects.toThrow(
+        "The selected repository list is empty. Please add repositories to it before running a variant analysis.",
       );
     });