Make emulator hub locator path more robust to environment changes

src/emulator/hub.ts

@@ -16,7 +16,7 @@
 import { maybeUsePortForwarding } from "./env";
 
 // We use the CLI version from package.json
 const pkg = require("../../package.json");
 
 export interface Locator {
   version: string;
@@ -33,7 +33,7 @@
 export type GetEmulatorsResponse = Partial<Record<Emulators, EmulatorInfo>>;
 
 export class EmulatorHub extends ExpressBasedEmulator {
   static CLI_VERSION = pkg.version;
   static PATH_EXPORT = "/_admin/export";
   static PATH_DISABLE_FUNCTIONS = "/functions/disableBackgroundTriggers";
   static PATH_ENABLE_FUNCTIONS = "/functions/enableBackgroundTriggers";
@@ -64,9 +64,12 @@
   }
 
   static getLocatorFilePath(projectId: string): string {
-    const dir = os.tmpdir();
-    const filename = `hub-${projectId}.json`;
-    return path.join(dir, filename);
+    return path.join(
+      os.homedir(),
+        ".cache",
+        "firebase",
+        `hub-${projectId}.json`,
+      );
   }
 
   constructor(private args: EmulatorHubArgs) {
@@ -106,14 +109,14 @@
       res.json(this.getRunningEmulatorsMapping());
     });
 
     app.post(EmulatorHub.PATH_EXPORT, async (req, res) => {
       if (req.headers.origin) {
         res.status(403).json({
           message: `Export cannot be triggered by external callers.`,
         });
       }
       const path: string = req.body.path;
       const initiatedBy: string = req.body.initiatedBy || "unknown";
       utils.logLabeledBullet("emulators", `Received export request. Exporting data to ${path}.`);
       try {
         await new HubExport(this.args.projectId, {
@@ -124,7 +127,7 @@
         res.status(200).send({
           message: "OK",
         });
       } catch (e: any) {
         const errorString = e.message || JSON.stringify(e);
         utils.logLabeledWarning("emulators", `Export failed: ${errorString}`);
         res.status(500).json({

src/mcp/index.ts

@@ -111,7 +111,7 @@ export class FirebaseMcpServer {
 
   async getEmulatorHubClient(): Promise<EmulatorHubClient | undefined> {
     // Single initilization
-    if (this.emulatorHubClient) {
+    if (this.emulatorHubClient && this.emulatorHubClient.foundHub()) {
       return this.emulatorHubClient;
     }
     const projectId = await this.getProjectId();