Add a retry to the DevTools handler for static files

Change-Id: Iced8093f894afd5574e3ae898e07f237e02002bf
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/325323
Reviewed-by: Derek Xu <derekx@google.com>
Commit-Queue: Kenzie Davisson <kenzieschmoll@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>

pkg/dds/CHANGELOG.md

@@ -1,12 +1,16 @@
+# 2.11.0
+- Added a retry to the DevTools handler for serving static files.
+- Updated `devtools_shared` to ^4.0.0.
+
 # 2.10.0
-- Updated `devtools_shared` to ^3.0.0
+- Updated `devtools_shared` to ^3.0.0.
 
 # 2.9.5
 - [DAP] The change to use VM Service Isolate numbers for `threadId`s has been reverted because Isolate numbers can be larger than the 32-bit integers allowed in DAP.
 - [DAP] Threads returned from `threadsRequest` from the DDS DAP handler now include `isolateId` fields to allow mapping back to VM Service Isolates.
 
 # 2.9.4
-- Updated `devtools_shared` to ^2.26.1
+- Updated `devtools_shared` to ^2.26.1.
 
 # 2.9.3
 - [DAP] `threadId`s generated by the debug adapter now match the Isolate numbers of the underlying isolates.

pkg/dds/lib/src/devtools/handler.dart

@@ -5,6 +5,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:typed_data';
 
 import 'package:devtools_shared/devtools_deeplink.dart';
 import 'package:devtools_shared/devtools_extensions_io.dart';
@@ -165,7 +166,17 @@ Future<Response> _serveStaticFile(
   final headers = {HttpHeaders.contentTypeHeader: contentType};
 
   if (contentType != 'text/html') {
-    return Response.ok(file.readAsBytesSync(), headers: headers);
+    late final Uint8List fileBytes;
+    try {
+      fileBytes = file.readAsBytesSync();
+    } on PathNotFoundException catch (_) {
+      // Wait a short delay, and then retry in case we have hit a race condition
+      // between a static file being served and accessed. See
+      // https://github.com/flutter/devtools/issues/6365.
+      await Future.delayed(Duration(milliseconds: 500));
+      fileBytes = file.readAsBytesSync();
+    }
+    return Response.ok(fileBytes, headers: headers);
   }
 
   var contents = file.readAsStringSync();

pkg/dds/pubspec.yaml

@@ -1,5 +1,5 @@
 name: dds
-version: 2.10.0
+version: 2.11.0
 description: >-
   A library used to spawn the Dart Developer Service, used to communicate with
   a Dart VM Service instance.