add a further guard against #643

cmd/esbuild/service.go

@@ -14,6 +14,7 @@ import (
 	"regexp"
 	"runtime/debug"
 	"sync"
+	"time"
 
 	"github.com/evanw/esbuild/internal/cli_helpers"
 	"github.com/evanw/esbuild/internal/config"
@@ -64,7 +65,9 @@ func runService() {
 			if !ok {
 				break // No more packets
 			}
-			os.Stdout.Write(packet.bytes)
+			if _, err := os.Stdout.Write(packet.bytes); err != nil {
+				os.Exit(1) // I/O error
+			}
 
 			// Only signal that this request is done when it has actually been written
 			if packet.refCount != 0 {
@@ -76,6 +79,19 @@ func runService() {
 	// The protocol always starts with the version
 	os.Stdout.Write(append(writeUint32(nil, uint32(len(esbuildVersion))), esbuildVersion...))
 
+	// Periodically ping the host even when we're idle. This will catch cases
+	// where the host has disappeared and will never send us anything else but
+	// we incorrectly think we are still needed. In that case we will now try
+	// to write to stdout and fail, and then know that we should exit.
+	go func() {
+		for {
+			time.Sleep(1 * time.Second)
+			service.sendRequest(map[string]interface{}{
+				"command": "ping",
+			})
+		}
+	}()
+
 	for {
 		// Read more data from stdin
 		n, err := os.Stdin.Read(buffer)

lib/common.ts

@@ -446,6 +446,7 @@ export function createChannel(streamIn: StreamIn): StreamOut {
   };
 
   type RequestType =
+    | protocol.PingRequest
     | protocol.OnResolveRequest
     | protocol.OnLoadRequest
     | protocol.OnRequestRequest
@@ -456,6 +457,11 @@ export function createChannel(streamIn: StreamIn): StreamOut {
     // Catch exceptions in the code below so they get passed to the caller
     try {
       switch (request.command) {
+        case 'ping': {
+          sendResponse(id, {});
+          break;
+        }
+
         case 'resolve': {
           let callback = pluginCallbacks.get(request.key);
           sendResponse(id, await callback!(request) as any);

lib/stdio_protocol.ts

@@ -55,6 +55,10 @@ export interface BuildOutputFile {
   contents: Uint8Array;
 }
 
+export interface PingRequest {
+  command: 'ping';
+}
+
 export interface RebuildRequest {
   command: 'rebuild';
   rebuildID: number;

scripts/browser/browser-tests.js

@@ -251,10 +251,9 @@ async function main() {
   }
 
   for (let key in pages) {
-    promises.push(runPage(key))
+    await runPage(key)
   }
 
-  await Promise.all(promises)
   await browser.close()
   server.close()