Make sure Auto doesn't behave as None and fail for developers

This situation can only happen if discoverVersionManager() fails to
detect any version manager and leaves identifier as 'auto',
which should never happen since `None` is the fallback. This is just an
additional safety check to catch bugs early.

Author: rafaelfranca

vscode/src/ruby.ts

@@ -45,7 +45,7 @@ interface ManagerClass {
   detect: (workspaceFolder: vscode.WorkspaceFolder, outputChannel: WorkspaceChannel) => Promise<DetectionResult>;
 }
 
-const VERSION_MANAGERS: Record<ManagerIdentifier, ManagerClass> = {
+const VERSION_MANAGERS: Record<ManagerIdentifier, ManagerClass | undefined> = {
   [ManagerIdentifier.Shadowenv]: Shadowenv,
   [ManagerIdentifier.Asdf]: Asdf,
   [ManagerIdentifier.Chruby]: Chruby,
@@ -55,8 +55,8 @@ const VERSION_MANAGERS: Record<ManagerIdentifier, ManagerClass> = {
   [ManagerIdentifier.Mise]: Mise,
   [ManagerIdentifier.RubyInstaller]: RubyInstaller,
   [ManagerIdentifier.Custom]: Custom,
-  [ManagerIdentifier.Auto]: None, // Auto is handled specially
   [ManagerIdentifier.None]: None, // None is last as the fallback
+  [ManagerIdentifier.Auto]: undefined, // Auto is handled specially
 };
 
 export class Ruby implements RubyInterface {
@@ -294,6 +294,15 @@ export class Ruby implements RubyInterface {
 
   private async runManagerActivation() {
     const ManagerClass = VERSION_MANAGERS[this.versionManager.identifier];
+
+    if (!ManagerClass) {
+      throw new Error(
+        `BUG: No ManagerClass found for identifier '${this.versionManager.identifier}'. ` +
+          `This indicates either: (1) discoverVersionManager() failed to detect any version manager and left identifier as 'auto', ` +
+          `or (2) a new ManagerIdentifier enum value was added without updating VERSION_MANAGERS.`,
+      );
+    }
+
     const manager = new ManagerClass(
       this.workspaceFolder,
       this.outputChannel,