dev playground: Support auto port assignment + refactor

packages/playground/devEnv/build.ts

@@ -3,7 +3,7 @@ import {writeFile, readFile} from 'fs/promises'
 import path from 'path'
 import type {BuildOptions} from 'esbuild'
 import esbuild from 'esbuild'
-import type {ServerResponse} from 'http'
+import type {IncomingMessage, ServerResponse} from 'http'
 import {definedGlobals} from '../../../theatre/devEnv/buildUtils'
 import {mapValues} from 'lodash-es'
 import {createServer, request} from 'http'
@@ -11,17 +11,57 @@ import {spawn} from 'child_process'
 import React from 'react'
 import {renderToStaticMarkup} from 'react-dom/server'
 import {Home} from './Home'
+import type {Server} from 'net'
 
-const playgroundDir = path.join(__dirname, '..')
-const buildDir = path.join(playgroundDir, 'build')
-const sharedDir = path.join(playgroundDir, 'src/shared')
-const personalDir = path.join(playgroundDir, 'src/personal')
-const testDir = path.join(playgroundDir, 'src/tests')
+const playgroundDir = (folder: string) => path.join(__dirname, '..', folder)
+const buildDir = playgroundDir('build')
+const sharedDir = playgroundDir('src/shared')
+const personalDir = playgroundDir('src/personal')
+const testDir = playgroundDir('src/tests')
 
-const dev = /^--dev|-d$/.test(process.argv[process.argv.length - 1])
-const port = 8080
+const dev = process.argv.find((arg) => ['--dev', '-d'].includes(arg)) != null
+const defaultPort = 8080
 
-const clients: ServerResponse[] = []
+const liveReload =
+  (dev || undefined) &&
+  ((): {
+    handleRequest(req: IncomingMessage, res: ServerResponse): boolean
+    hasOpenConnections(): boolean
+    esbuildBanner: esbuild.BuildOptions['banner']
+    esbuildWatch: esbuild.WatchMode
+  } => {
+    const openResponses: ServerResponse[] = []
+    return {
+      handleRequest(req, res) {
+        // If special /esbuild url requested, subscribe clients to changes
+        if (req.url === '/esbuild') {
+          openResponses.push(
+            res.writeHead(200, {
+              'Content-Type': 'text/event-stream',
+              'Cache-Control': 'no-cache',
+              Connection: 'keep-alive',
+            }),
+          )
+          return true
+        }
+        return false
+      },
+      hasOpenConnections() {
+        return openResponses.length > 0
+      },
+      esbuildBanner: {
+        js: ' (() => new EventSource("/esbuild").onmessage = () => location.reload())();',
+      },
+      esbuildWatch: {
+        onRebuild(error) {
+          // Notify clients on rebuild
+          openResponses.forEach((res) => res.write('data: update\n\n'))
+          openResponses.length = 0
+          console.error(error ? error : 'Reloading...')
+        },
+      },
+    }
+  })()
 
 type Groups = {
   [group: string]: {
@@ -40,11 +80,15 @@ const groups: Groups = Object.fromEntries(
         return [
           path.basename(groupDir),
           Object.fromEntries(
-            readdirSync(groupDir).map((moduleDir) => [
-              path.basename(moduleDir),
+            readdirSync(groupDir).map((moduleDirName) => [
+              path.basename(moduleDirName),
               {
-                entryDir: path.join(groupDir, moduleDir),
-                outDir: path.join(buildDir, path.basename(groupDir), moduleDir),
+                entryDir: path.join(groupDir, moduleDirName),
+                outDir: path.join(
+                  buildDir,
+                  path.basename(groupDir),
+                  moduleDirName,
+                ),
               },
             ]),
           ),
@@ -79,7 +123,7 @@ const config: BuildOptions = {
   entryPoints,
   bundle: true,
   sourcemap: true,
-  outdir: path.join(playgroundDir, 'build'),
+  outdir: playgroundDir('build'),
   target: ['firefox88'],
   loader: {
     '.png': 'file',
@@ -91,19 +135,8 @@ const config: BuildOptions = {
     ...definedGlobals,
     'window.__IS_VISUAL_REGRESSION_TESTING': 'true',
   },
-  banner: dev
-    ? {
-        js: ' (() => new EventSource("/esbuild").onmessage = () => location.reload())();',
-      }
-    : undefined,
-  watch: dev && {
-    onRebuild(error) {
-      // Notify clients on rebuild
-      clients.forEach((res) => res.write('data: update\n\n'))
-      clients.length = 0
-      console.log(error ? error : 'Reloading...')
-    },
-  },
+  banner: liveReload?.esbuildBanner,
+  watch: liveReload?.esbuildWatch,
 }
 
 esbuild
@@ -134,7 +167,7 @@ esbuild
     console.log(err)
     return process.exit(1)
   })
-  .then(() => {
+  .then(async () => {
     // Only start dev server in dev, otherwise just run build and that's it
     if (!dev) {
       return
@@ -142,22 +175,17 @@ esbuild
 
     // We start ESBuild serve with no build config because it doesn't need to build
     // anything, we are already using ESBuild watch.
-    esbuild
-      .serve({servedir: path.join(playgroundDir, 'build')}, {})
-      .then(({port: esbuildPort}) => {
-        // Create proxy
-        createServer((req, res) => {
-          const {url, method, headers} = req
-          // If special /esbuild url requested, subscribe clients to changes
-          if (req.url === '/esbuild') {
-            return clients.push(
-              res.writeHead(200, {
-                'Content-Type': 'text/event-stream',
-                'Cache-Control': 'no-cache',
-                Connection: 'keep-alive',
-              }),
+    const {port: esbuildPort} = await esbuild.serve(
+      {servedir: playgroundDir('build')},
+      {},
     )
+
+    const proxyServer = createServer((req, res) => {
+      const {url, method, headers} = req
+      if (liveReload?.handleRequest(req, res)) {
+        return
       }
+
       // Otherwise forward requests to ESBuild server
       req.pipe(
         request(
@@ -175,25 +203,86 @@ esbuild
         ),
         {end: true},
       )
-        }).listen(port, () => {
-          console.log('Playground running at', 'http://localhost:' + port)
     })
 
+    const isCI = process.env.CI
+    const portTries = isCI ? 1 : 10
+    const portChosen = await tryMultiplePorts(
+      defaultPort,
+      portTries,
+      proxyServer,
+    )
+
+    const hostedAt = `http://localhost:${portChosen}`
+
+    console.log('Playground running at', hostedAt)
+
     // If not in CI, try to spawn a browser
-        if (!process.env.CI) {
+    if (!isCI) {
       setTimeout(() => {
+        if (!liveReload?.hasOpenConnections()) openForOS(hostedAt)
+      }, 1000)
+    }
+  })
+
+function openForOS(hostedAt: string) {
   const open = {
     darwin: ['open'],
     linux: ['xdg-open'],
     win32: ['cmd', '/c', 'start'],
   }
   const platform = process.platform as keyof typeof open
-            if (clients.length === 0)
-              spawn(open[platform][0], [
-                ...open[platform].slice(1),
-                `http://localhost:${port}`,
-              ])
-          }, 1000)
+  if (open[platform]) {
+    spawn(open[platform][0], [...open[platform].slice(1), hostedAt])
+  } else {
+    console.error(
+      `Failed to open (${hostedAt}) for unconfigured platform (${platform})`,
+    )
   }
+}
+
+async function tryMultiplePorts(
+  port: number,
+  tries: number,
+  server: Server,
+): Promise<number> {
+  let portToTry = port
+  let firstError = null
+  let lastError = null
+
+  while (portToTry < port + tries) {
+    try {
+      await new Promise((res, rej) => {
+        const onListening = () => (rm(), res(true))
+        const onError = () => (rm(), rej())
+        const rm = () => {
+          server.off('error', onError)
+          server.off('listening', onListening)
+        }
+
+        server
+          .listen(portToTry)
+          .on('listening', onListening)
+          .on('error', onError)
       })
-  })
+
+      firstError = null
+      lastError = null
+      break // found a working port
+    } catch (err) {
+      if (!firstError) firstError = err
+      lastError = err
+      portToTry += 1
+    }
+  }
+
+  if (firstError) {
+    console.error(firstError)
+    console.error(lastError)
+    throw new Error(
+      `Failed to find port starting at ${port} with ${tries} tries.`,
+    )
+  }
+
+  return portToTry
+}