fix: add functions build wait for docker emulator

packages/documentation/docs/Backend Development/firebase-emulators-docker.md

@@ -44,7 +44,9 @@ Note - any data populated into the emulator will be deleted after the emulator h
 
 ## Resetting seed data
 
-When the emulator is stopped the image is destroyed, so each time the emulators are restarted a clean set of data will be available
+When the emulator is stopped the image is destroyed, so each time the emulators are restarted a clean set of data will be available.
+
+If using the frontend data changes may still persist due to the browser's own caching mechanisms. In this case the browser indexeddb cache will need to be manually cleared
 
 ## Frontend
 

packages/emulators-docker/src/start.ts

@@ -1,6 +1,7 @@
 import Dockerode from 'dockerode'
 import boxen from 'boxen'
 import logUpdate from 'log-update'
+import fs from 'fs-extra'
 import {
   CONTAINER_NAME,
   getFirebasePortMapping,
@@ -95,11 +96,18 @@ function attachContainer(container: Dockerode.Container) {
 }
 
 async function createNewContainer() {
+  // ensure functions dist exists for binding
+  if (!fs.existsSync(PATHS.functionsDistIndex)) {
+    console.log('Waiting for functions to be built...')
+    await _wait(5000)
+    return createNewContainer()
+  }
+  // pull remote image if required
   if (REPOSITORY) {
     await pullRemoteImage(IMAGE_NAME)
   }
   const { ExposedPorts, PortBindings } = rewritePortMapping()
-  return new Promise<Dockerode.Container>((resolve, reject) => {
+  return new Promise<Dockerode.Container>(async (resolve, reject) => {
     docker.createContainer(
       {
         // Image: 'goatlab/firebase-emulator:latest',
@@ -237,4 +245,11 @@ function execContainerCmd(container: Dockerode.Container, Cmd: string[]) {
   )
 }
 
+/** Wait an aribitrary number of milliseconds before continuing */
+async function _wait(ms: number) {
+  return new Promise((resolve) => {
+    setTimeout(resolve, ms)
+  })
+}
+
 start()