Stop user from adding a db list with the same name

extensions/ql-vscode/src/databases/config/db-config-store.ts

@@ -99,16 +99,29 @@ export class DbConfigStore extends DisposableObject {
       throw Error("Cannot add remote list if config is not loaded");
     }
 
+    if (this.doesRemoteListExist(listName)) {
+      throw Error(`A remote list with the name '${listName}' already exists`);
+    }
+
     const config: DbConfig = cloneDbConfig(this.config);
     config.databases.remote.repositoryLists.push({
       name: listName,
       repositories: [],
     });
 
-    // TODO: validate that the name doesn't already exist
     await this.writeConfig(config);
   }
 
+  public doesRemoteListExist(listName: string): boolean {
+    if (!this.config) {
+      throw Error("Cannot check remote list existence if config is not loaded");
+    }
+
+    return this.config.databases.remote.repositoryLists.some(
+      (l) => l.name === listName,
+    );
+  }
+
   private async writeConfig(config: DbConfig): Promise<void> {
     await writeJSON(this.configPath, config, {
       spaces: 2,

extensions/ql-vscode/src/databases/db-manager.ts

@@ -76,6 +76,14 @@ export class DbManager {
   }
 
   public async addNewRemoteList(listName: string): Promise<void> {
+    if (this.dbConfigStore.doesRemoteListExist(listName)) {
+      throw Error(`A list with the name '${listName}' already exists`);
+    }
+
     await this.dbConfigStore.addRemoteList(listName);
   }
+
+  public doesRemoteListExist(listName: string): boolean {
+    return this.dbConfigStore.doesRemoteListExist(listName);
+  }
 }

extensions/ql-vscode/src/databases/ui/db-panel.ts

@@ -1,5 +1,6 @@
 import { TreeViewExpansionEvent, window, workspace } from "vscode";
 import { commandRunner } from "../../commandRunner";
+import { showAndLogErrorMessage } from "../../helpers";
 import { DisposableObject } from "../../pure/disposable-object";
 import { DbManager } from "../db-manager";
 import { DbTreeDataProvider } from "./db-tree-data-provider";
@@ -58,15 +59,21 @@ export class DbPanel extends DisposableObject {
   }
 
   private async addNewRemoteList(): Promise<void> {
-    // TODO: check that config exists *before* showing the input box
     const listName = await window.showInputBox({
       prompt: "Enter a name for the new list",
       placeHolder: "example-list",
     });
     if (listName === undefined) {
       return;
     }
-    await this.dbManager.addNewRemoteList(listName);
+
+    if (this.dbManager.doesRemoteListExist(listName)) {
+      void showAndLogErrorMessage(
+        `A list with the name '${listName}' already exists`,
+      );
+    } else {
+      await this.dbManager.addNewRemoteList(listName);
+    }
   }
 
   private async setSelectedItem(treeViewItem: DbTreeViewItem): Promise<void> {