Allow MCP to use ADC (#8735)

* Allow MCP to use ADC

* Refactor

* PR fixes

Author: joehan

CHANGELOG.md

@@ -3,3 +3,4 @@
 - Add validation during `firebase init` feature selection. (#5232)
 - Fixed an issue where the extensions emulator did not work with `demo-` projects. (#8720)
 - Fixed issue where `--export-on-exit` fails if the target directory does not exist. (#4688)
+- Fixed issue where the Firebase MCP server could not use application default credentials. (#8671)

src/mcp/index.ts

@@ -174,7 +174,8 @@ export class FirebaseMcpServer {
 
   async getAuthenticatedUser(): Promise<string | null> {
     try {
-      return await requireAuth(await this.resolveOptions());
+      const email = await requireAuth(await this.resolveOptions());
+      return email ?? "Application Default Credentials";
     } catch (e) {
       return null;
     }

src/requireAuth.ts

@@ -77,7 +77,9 @@ export async function refreshAuth(): Promise<Tokens> {
 }
 
 /**
- * Ensures that there is an authenticated user.
+ * Ensures that the user can make authenticated calls. Returns the email if the user is logged in,
+ * returns null if the user has Applciation Default Credentials set up, and errors out
+ * if the user is not authenticated
  * @param options CLI options.
  */
 export async function requireAuth(options: any): Promise<string | null> {