fix(core): prioritize detailed error messages for code assist setup (#17852)

packages/core/src/code_assist/setup.ts

@@ -7,6 +7,7 @@
 import type {
   ClientMetadata,
   GeminiUserTier,
+  IneligibleTier,
   LoadCodeAssistResponse,
   OnboardUserRequest,
 } from './types.js';
@@ -35,6 +36,16 @@ export class ValidationCancelledError extends Error {
   }
 }
 
+export class IneligibleTierError extends Error {
+  readonly ineligibleTiers: IneligibleTier[];
+
+  constructor(ineligibleTiers: IneligibleTier[]) {
+    const reasons = ineligibleTiers.map((t) => t.reasonMessage).join(', ');
+    super(reasons);
+    this.ineligibleTiers = ineligibleTiers;
+  }
+}
+
 export interface UserData {
   projectId: string;
   userTier: UserTierId;
@@ -127,13 +138,7 @@ export async function setupUser(
       }
 
       // If user is not setup for standard tier, inform them about all other tiers they are ineligible for.
-      if (loadRes.ineligibleTiers && loadRes.ineligibleTiers.length > 0) {
-        const reasons = loadRes.ineligibleTiers
-          .map((t) => t.reasonMessage)
-          .join(', ');
-        throw new Error(reasons);
-      }
-      throw new ProjectIdRequiredError();
+      throwIneligibleOrProjectIdError(loadRes);
     }
     return {
       projectId: loadRes.cloudaicompanionProject,
@@ -180,7 +185,8 @@ export async function setupUser(
         userTierName: tier.name,
       };
     }
-    throw new ProjectIdRequiredError();
+
+    throwIneligibleOrProjectIdError(loadRes);
   }
 
   return {
@@ -190,6 +196,13 @@ export async function setupUser(
   };
 }
 
+function throwIneligibleOrProjectIdError(res: LoadCodeAssistResponse): never {
+  if (res.ineligibleTiers && res.ineligibleTiers.length > 0) {
+    throw new IneligibleTierError(res.ineligibleTiers);
+  }
+  throw new ProjectIdRequiredError();
+}
+
 function getOnboardTier(res: LoadCodeAssistResponse): GeminiUserTier {
   for (const tier of res.allowedTiers || []) {
     if (tier.isDefault) {