Improve logging when emulators are not starting (#3021)

Author: samtstern

CHANGELOG.md

@@ -1,4 +1 @@
-- Add warning when a developer is using yarn@2 PnP (#2198).
-- Fixes incorrect URLs reported inside emulated HTTPS functions (#1862).
-- Updates underlying timeout handler when proxying through the Hosting emulator.
-- Adds support for installing [experimental extensions](https://github.com/FirebaseExtended/experimental-extensions) (#2830)
+- Improves logging for `emulators:start` and `emulators:exec` (#3020).

src/commands/emulators-start.ts

@@ -40,6 +40,8 @@ module.exports = new Command("emulators:start")
         reservedPorts.push(info.port);
       }
     }
+    const reservedPortsString = reservedPorts.length > 0 ? reservedPorts.join(", ") : "None";
+
     const uiInfo = EmulatorRegistry.getInfo(Emulators.UI);
     const hubInfo = EmulatorRegistry.getInfo(Emulators.HUB);
     const uiUrl = uiInfo ? `http://${EmulatorRegistry.getInfoHostString(uiInfo)}` : "unknown";
@@ -97,7 +99,7 @@ ${
     ? clc.blackBright("  Emulator Hub running at ") + EmulatorRegistry.getInfoHostString(hubInfo)
     : clc.blackBright("  Emulator Hub not running.")
 }
-${clc.blackBright("  Other reserved ports:")} ${reservedPorts.join(", ")}
+${clc.blackBright("  Other reserved ports:")} ${reservedPortsString}
 
 Issues? Report them at ${stylizeLink(
       "https://github.com/firebase/firebase-tools/issues"

src/emulator/commandUtils.ts

@@ -405,8 +405,8 @@ export async function emulatorExec(script: string, options: any) {
   }
   let exitCode = 0;
   try {
-    const excludeUi = !options.ui;
-    await controller.startAll(options, excludeUi);
+    const showUI = !!options.ui;
+    await controller.startAll(options, showUI);
     exitCode = await runScript(script, extraEnv);
     await onExit(options);
   } finally {

src/emulator/controller.ts

@@ -291,7 +291,7 @@ function findExportMetadata(importPath: string): ExportMetadata | undefined {
   }
 }
 
-export async function startAll(options: any, noUi: boolean = false): Promise<void> {
+export async function startAll(options: any, showUI: boolean = true): Promise<void> {
   // Emulators config is specified in firebase.json as:
   // "emulators": {
   //   "firestore": {
@@ -309,6 +309,12 @@ export async function startAll(options: any, noUi: boolean = false): Promise<voi
 
   const projectId: string | undefined = getProjectId(options, true);
 
+  if (targets.length === 0) {
+    throw new FirebaseError(
+      `No emulators to start, run ${clc.bold("firebase init emulators")} to get started.`
+    );
+  }
+
   EmulatorLogger.forEmulator(Emulators.HUB).logLabeled(
     "BULLET",
     "emulators",
@@ -588,7 +594,15 @@ export async function startAll(options: any, noUi: boolean = false): Promise<voi
     await startEmulator(hostingEmulator);
   }
 
-  if (!noUi && shouldStart(options, Emulators.UI)) {
+  if (showUI && !shouldStart(options, Emulators.UI)) {
+    EmulatorLogger.forEmulator(Emulators.HUB).logLabeled(
+      "WARN",
+      "emulators",
+      "The Emulator UI requires a project ID to start. Configure your default project with 'firebase use' or pass the ---project flag."
+    );
+  }
+
+  if (showUI && shouldStart(options, Emulators.UI)) {
     const loggingAddr = await getAndCheckAddress(Emulators.LOGGING, options);
     const loggingEmulator = new LoggingEmulator({
       host: loggingAddr.host,