From d114fd3f890781cf52b912c1a80bbc65c3c0326d Mon Sep 17 00:00:00 2001
From: Andrew Kolos <andrewrkolos@gmail.com>
Date: Thu, 25 Jul 2024 22:28:35 -0700
Subject: [PATCH 1/7] init

---
 packages/flutter_tools/lib/src/compile.dart   | 118 ++++++++++--------
 packages/flutter_tools/lib/src/devfs.dart     |   2 +-
 .../lib/src/isolated/devfs_web.dart           |   2 +-
 .../lib/src/isolated/resident_web_runner.dart |   4 +-
 .../lib/src/resident_runner.dart              |   2 +-
 packages/flutter_tools/lib/src/run_hot.dart   |   4 +-
 .../flutter_tools/lib/src/test/runner.dart    |   2 +-
 .../lib/src/test/test_compiler.dart           |   4 +-
 .../compile_incremental_test.dart             |   2 +-
 .../test/general.shard/hot_shared.dart        |   2 +-
 .../resident_runner_helpers.dart              |   4 +-
 .../resident_web_runner_test.dart             |   4 +-
 .../test/test_compiler_test.dart              |   4 +-
 13 files changed, 86 insertions(+), 68 deletions(-)

diff --git a/packages/flutter_tools/lib/src/compile.dart b/packages/flutter_tools/lib/src/compile.dart
index f1ce205dbfc5b..4cb61033ed2b0 100644
--- a/packages/flutter_tools/lib/src/compile.dart
+++ b/packages/flutter_tools/lib/src/compile.dart
@@ -16,6 +16,7 @@ import 'base/file_system.dart';
 import 'base/io.dart';
 import 'base/logger.dart';
 import 'base/platform.dart';
+import 'base/process.dart';
 import 'build_info.dart';
 import 'convert.dart';
 
@@ -589,7 +590,7 @@ abstract class ResidentCompiler {
   /// Should be invoked when results of compilation are accepted by the client.
   ///
   /// Either [accept] or [reject] should be called after every [recompile] call.
-  void accept();
+  Future<void> accept();
 
   /// Should be invoked when results of compilation are rejected by the client.
   ///
@@ -599,7 +600,7 @@ abstract class ResidentCompiler {
   /// Should be invoked when frontend server compiler should forget what was
   /// accepted previously so that next call to [recompile] produces complete
   /// kernel file.
-  void reset();
+  Future<void> reset();
 
   Future<Object> shutdown();
 }
@@ -742,11 +743,9 @@ class DefaultResidentCompiler implements ResidentCompiler {
     final String inputKey = Uuid().generateV4();
 
     if (nativeAssets != null && nativeAssets.isNotEmpty) {
-      server.stdin.writeln('native-assets $nativeAssets');
-      _logger.printTrace('<- native-assets $nativeAssets');
+      await _writelnToServerStdin('native-assets $nativeAssets', printTrace: true);
     }
-    server.stdin.writeln('recompile $mainUri $inputKey');
-    _logger.printTrace('<- recompile $mainUri $inputKey');
+    await _writelnToServerStdin('recompile $mainUri $inputKey', printTrace: true);
     final List<Uri>? invalidatedFiles = request.invalidatedFiles;
     if (invalidatedFiles != null) {
       for (final Uri fileUri in invalidatedFiles) {
@@ -761,8 +760,7 @@ class DefaultResidentCompiler implements ResidentCompiler {
         _logger.printTrace(message);
       }
     }
-    server.stdin.writeln(inputKey);
-    _logger.printTrace('<- $inputKey');
+    await _writelnToServerStdin(inputKey, printTrace: true);
 
     return _stdoutHandler.compilerOutput?.future;
   }
@@ -899,12 +897,10 @@ class DefaultResidentCompiler implements ResidentCompiler {
     }));
 
     if (nativeAssetsUri != null && nativeAssetsUri.isNotEmpty) {
-      _server?.stdin.writeln('native-assets $nativeAssetsUri');
-      _logger.printTrace('<- native-assets $nativeAssetsUri');
+      await _writelnToServerStdin('native assets $nativeAssetsUri', printTrace: true);
     }
 
-    _server?.stdin.writeln('compile $scriptUri');
-    _logger.printTrace('<- compile $scriptUri');
+    await _writelnToServerStdin('compile $scriptUri', printTrace: true);
 
     return _stdoutHandler.compilerOutput?.future;
   }
@@ -945,24 +941,24 @@ class DefaultResidentCompiler implements ResidentCompiler {
     }
 
     final String inputKey = Uuid().generateV4();
-    server.stdin
-      ..writeln('compile-expression $inputKey')
-      ..writeln(request.expression);
-    request.definitions?.forEach(server.stdin.writeln);
-    server.stdin.writeln(inputKey);
-    request.definitionTypes?.forEach(server.stdin.writeln);
-    server.stdin.writeln(inputKey);
-    request.typeDefinitions?.forEach(server.stdin.writeln);
-    server.stdin.writeln(inputKey);
-    request.typeBounds?.forEach(server.stdin.writeln);
-    server.stdin.writeln(inputKey);
-    request.typeDefaults?.forEach(server.stdin.writeln);
-    server.stdin
-      ..writeln(inputKey)
-      ..writeln(request.libraryUri ?? '')
-      ..writeln(request.klass ?? '')
-      ..writeln(request.method ?? '')
-      ..writeln(request.isStatic);
+    await _writelnToServerStdinAll(<String>[
+      'compile-expression $inputKey',
+      request.expression,
+      ...?request.definitions,
+      inputKey,
+      ...?request.definitionTypes,
+      inputKey,
+      ...?request.typeDefinitions,
+      inputKey,
+      ...?request.typeBounds,
+      inputKey,
+      ...?request.typeDefaults,
+      inputKey,
+      request.libraryUri ?? '',
+      request.klass ?? '',
+      request.method ?? '',
+      request.isStatic.toString(),
+    ]);
 
     return _stdoutHandler.compilerOutput?.future;
   }
@@ -1000,27 +996,28 @@ class DefaultResidentCompiler implements ResidentCompiler {
     }
 
     final String inputKey = Uuid().generateV4();
-    server.stdin
-      ..writeln('compile-expression-to-js $inputKey')
-      ..writeln(request.libraryUri ?? '')
-      ..writeln(request.line)
-      ..writeln(request.column);
-    request.jsModules?.forEach((String k, String v) { server.stdin.writeln('$k:$v'); });
-    server.stdin.writeln(inputKey);
-    request.jsFrameValues?.forEach((String k, String v) { server.stdin.writeln('$k:$v'); });
-    server.stdin
-      ..writeln(inputKey)
-      ..writeln(request.moduleName ?? '')
-      ..writeln(request.expression ?? '');
+    await _writelnToServerStdinAll(<String>[
+      'compile-expression-to-js $inputKey',
+      request.libraryUri ?? '',
+      request.line.toString(),
+      request.column.toString(),
+      for (final MapEntry<String, String> entry in request.jsModules?.entries ?? <MapEntry<String, String>>[])
+        '${entry.key}:${entry.value}',
+      inputKey,
+      for (final MapEntry<String, String> entry in request.jsFrameValues?.entries ?? <MapEntry<String, String>>[])
+        '${entry.key}:${entry.value}',
+      inputKey,
+      request.moduleName ?? '',
+      request.expression ?? ''
+    ]);
 
     return _stdoutHandler.compilerOutput?.future;
   }
 
   @override
-  void accept() {
+  Future<void> accept() async {
     if (_compileRequestNeedsConfirmation) {
-      _server?.stdin.writeln('accept');
-      _logger.printTrace('<- accept');
+      await _writelnToServerStdin('accept', printTrace: true);
     }
     _compileRequestNeedsConfirmation = false;
   }
@@ -1041,16 +1038,14 @@ class DefaultResidentCompiler implements ResidentCompiler {
       return Future<CompilerOutput?>.value();
     }
     _stdoutHandler.reset(expectSources: false);
-    _server?.stdin.writeln('reject');
-    _logger.printTrace('<- reject');
+    await _writelnToServerStdin('reject', printTrace: true);
     _compileRequestNeedsConfirmation = false;
     return _stdoutHandler.compilerOutput?.future;
   }
 
   @override
-  void reset() {
-    _server?.stdin.writeln('reset');
-    _logger.printTrace('<- reset');
+  Future<void> reset() async {
+    await _writelnToServerStdin('reset', printTrace: true);
   }
 
   @override
@@ -1064,6 +1059,29 @@ class DefaultResidentCompiler implements ResidentCompiler {
     server.kill();
     return server.exitCode;
   }
+
+  Future<void> _writelnToServerStdin(String line, {
+    bool printTrace = false,
+  }) async {
+    final Process? server = _server;
+    if (server == null) {
+      return;
+    }
+    await ProcessUtils.writelnToStdinUnsafe(stdin: server.stdin, line: line);
+    if (printTrace) {
+      _logger.printTrace('<- $line');
+    }
+  }
+
+  Future<void> _writelnToServerStdinAll(List<String>? lines) async {
+    final Process? server = _server;
+    if (server == null) {
+      return;
+    }
+    for (final String line in lines ?? <String>[]) {
+      await ProcessUtils.writelnToStdinUnsafe(stdin: server.stdin, line: line);
+    }
+  }
 }
 
 /// Convert a file URI into a multi-root scheme URI if provided, otherwise
diff --git a/packages/flutter_tools/lib/src/devfs.dart b/packages/flutter_tools/lib/src/devfs.dart
index a38e9824d19d1..33b6339d647e7 100644
--- a/packages/flutter_tools/lib/src/devfs.dart
+++ b/packages/flutter_tools/lib/src/devfs.dart
@@ -585,7 +585,7 @@ class DevFS {
     bool assetBuildFailed = false;
     int syncedBytes = 0;
     if (fullRestart) {
-      generator.reset();
+      await generator.reset();
     }
     // On a full restart, or on an initial compile for the attach based workflow,
     // this will produce a full dill. Subsequent invocations will produce incremental
diff --git a/packages/flutter_tools/lib/src/isolated/devfs_web.dart b/packages/flutter_tools/lib/src/isolated/devfs_web.dart
index 690278ba67052..dc7c5299219c2 100644
--- a/packages/flutter_tools/lib/src/isolated/devfs_web.dart
+++ b/packages/flutter_tools/lib/src/isolated/devfs_web.dart
@@ -1020,7 +1020,7 @@ class WebDevFS implements DevFS {
     await _validateTemplateFile('flutter_bootstrap.js');
     final DateTime candidateCompileTime = DateTime.now();
     if (fullRestart) {
-      generator.reset();
+      await generator.reset();
     }
 
     // The tool generates an entrypoint file in a temp directory to handle
diff --git a/packages/flutter_tools/lib/src/isolated/resident_web_runner.dart b/packages/flutter_tools/lib/src/isolated/resident_web_runner.dart
index c212a0ed632d5..3a9d210a2ba2e 100644
--- a/packages/flutter_tools/lib/src/isolated/resident_web_runner.dart
+++ b/packages/flutter_tools/lib/src/isolated/resident_web_runner.dart
@@ -334,7 +334,7 @@ Please provide a valid TCP port (an integer between 0 and 65535, inclusive).
             appFailedToStart();
             return 1;
           }
-          device!.generator!.accept();
+          await device!.generator!.accept();
           cacheInitialDillCompilation();
         } else {
           final WebBuilder webBuilder = WebBuilder(
@@ -418,7 +418,7 @@ Please provide a valid TCP port (an integer between 0 and 65535, inclusive).
       // Full restart is always false for web, since the extra recompile is wasteful.
       final UpdateFSReport report = await _updateDevFS();
       if (report.success) {
-        device!.generator!.accept();
+        await device!.generator!.accept();
       } else {
         status.stop();
         await device!.generator!.reject();
diff --git a/packages/flutter_tools/lib/src/resident_runner.dart b/packages/flutter_tools/lib/src/resident_runner.dart
index daabad8b910ba..eefcf4ca3fe70 100644
--- a/packages/flutter_tools/lib/src/resident_runner.dart
+++ b/packages/flutter_tools/lib/src/resident_runner.dart
@@ -595,7 +595,7 @@ class FlutterDevice {
 
   Future<void> updateReloadStatus(bool wasReloadSuccessful) async {
     if (wasReloadSuccessful) {
-      generator?.accept();
+      await generator?.accept();
     } else {
       await generator?.reject();
     }
diff --git a/packages/flutter_tools/lib/src/run_hot.dart b/packages/flutter_tools/lib/src/run_hot.dart
index 2684e093b5604..b93724789007c 100644
--- a/packages/flutter_tools/lib/src/run_hot.dart
+++ b/packages/flutter_tools/lib/src/run_hot.dart
@@ -298,7 +298,7 @@ class HotRunner extends ResidentRunner {
       // VM must have accepted the kernel binary, there will be no reload
       // report, so we let incremental compiler know that source code was accepted.
       if (device!.generator != null) {
-        device.generator!.accept();
+        await device.generator!.accept();
       }
       final List<FlutterView> views = await device.vmService!.getFlutterViews();
       for (final FlutterView view in views) {
@@ -626,7 +626,7 @@ class HotRunner extends ResidentRunner {
       // VM must have accepted the kernel binary, there will be no reload
       // report, so we let incremental compiler know that source code was accepted.
       if (device!.generator != null) {
-        device.generator!.accept();
+        await device.generator!.accept();
       }
     }
     // Check if the isolate is paused and resume it.
diff --git a/packages/flutter_tools/lib/src/test/runner.dart b/packages/flutter_tools/lib/src/test/runner.dart
index 7bbadbb9185de..3181ef676b716 100644
--- a/packages/flutter_tools/lib/src/test/runner.dart
+++ b/packages/flutter_tools/lib/src/test/runner.dart
@@ -647,7 +647,7 @@ class SpawnPlugin extends PlatformPlugin {
       fs: globals.fs,
       nativeAssetsYaml: nativeAssetsYaml,
     );
-    residentCompiler.accept();
+    await residentCompiler.accept();
 
     globals.printTrace('Compiling ${sourceFile.absolute.uri} took ${compilerTime.elapsedMilliseconds}ms');
     testTimeRecorder?.stop(TestTimePhases.Compile, testTimeRecorderStopwatch!);
diff --git a/packages/flutter_tools/lib/src/test/test_compiler.dart b/packages/flutter_tools/lib/src/test/test_compiler.dart
index 9c09ba92c409b..a94688e9852bb 100644
--- a/packages/flutter_tools/lib/src/test/test_compiler.dart
+++ b/packages/flutter_tools/lib/src/test/test_compiler.dart
@@ -209,8 +209,8 @@ class TestCompiler {
         } else {
           request.result.complete(outputPath);
         }
-        compiler!.accept();
-        compiler!.reset();
+        await compiler!.accept();
+        await compiler!.reset();
       }
       globals.printTrace('Compiling ${request.mainUri} took ${compilerTime.elapsedMilliseconds}ms');
       testTimeRecorder?.stop(TestTimePhases.Compile, testTimeRecorderStopwatch!);
diff --git a/packages/flutter_tools/test/general.shard/compile_incremental_test.dart b/packages/flutter_tools/test/general.shard/compile_incremental_test.dart
index 14749ae1d458e..47c2a956fdf38 100644
--- a/packages/flutter_tools/test/general.shard/compile_incremental_test.dart
+++ b/packages/flutter_tools/test/general.shard/compile_incremental_test.dart
@@ -521,7 +521,7 @@ Future<void> _accept(
   MemoryIOSink frontendServerStdIn,
   String expected,
 ) async {
-  generator.accept();
+  await generator.accept();
   final String commands = frontendServerStdIn.getAndClear();
   final RegExp re = RegExp(expected);
   expect(commands, matches(re));
diff --git a/packages/flutter_tools/test/general.shard/hot_shared.dart b/packages/flutter_tools/test/general.shard/hot_shared.dart
index 39f0aa0da57fc..c76f5397f166a 100644
--- a/packages/flutter_tools/test/general.shard/hot_shared.dart
+++ b/packages/flutter_tools/test/general.shard/hot_shared.dart
@@ -192,7 +192,7 @@ class TestHotRunnerConfig extends HotRunnerConfig {
 
 class FakeResidentCompiler extends Fake implements ResidentCompiler {
   @override
-  void accept() {}
+  Future<void> accept() async {}
 }
 
 class FakeFlutterVmService extends Fake implements FlutterVmService {
diff --git a/packages/flutter_tools/test/general.shard/resident_runner_helpers.dart b/packages/flutter_tools/test/general.shard/resident_runner_helpers.dart
index 165c00d234de6..3bab03eb44ca5 100644
--- a/packages/flutter_tools/test/general.shard/resident_runner_helpers.dart
+++ b/packages/flutter_tools/test/general.shard/resident_runner_helpers.dart
@@ -346,10 +346,10 @@ class FakeResidentCompiler extends Fake implements ResidentCompiler {
   }
 
   @override
-  void accept() { }
+  Future<void> accept() async {}
 
   @override
-  void reset() { }
+  Future<void> reset() async {}
 }
 
 class FakeProjectFileInvalidator extends Fake implements ProjectFileInvalidator {
diff --git a/packages/flutter_tools/test/general.shard/resident_web_runner_test.dart b/packages/flutter_tools/test/general.shard/resident_web_runner_test.dart
index 563b0eac3038f..67858cad08004 100644
--- a/packages/flutter_tools/test/general.shard/resident_web_runner_test.dart
+++ b/packages/flutter_tools/test/general.shard/resident_web_runner_test.dart
@@ -1508,10 +1508,10 @@ class FakeResidentCompiler extends Fake implements ResidentCompiler {
   }
 
   @override
-  void accept() {}
+  Future<void> accept() async {}
 
   @override
-  void reset() {}
+  Future<void> reset() async {}
 
   @override
   Future<CompilerOutput> reject() async {
diff --git a/packages/flutter_tools/test/general.shard/test/test_compiler_test.dart b/packages/flutter_tools/test/general.shard/test/test_compiler_test.dart
index 257ad4f99966d..9585fbe9246a9 100644
--- a/packages/flutter_tools/test/general.shard/test/test_compiler_test.dart
+++ b/packages/flutter_tools/test/general.shard/test/test_compiler_test.dart
@@ -244,10 +244,10 @@ class FakeResidentCompiler extends Fake implements ResidentCompiler {
   }
 
   @override
-  void accept() { }
+  Future<void> accept() async {}
 
   @override
-  void reset() { }
+  Future<void> reset() async {}
 
   @override
   Future<Object> shutdown() async {

From d1b5b434490701527363feef0b065a0522a5b4a2 Mon Sep 17 00:00:00 2001
From: Andrew Kolos <andrewrkolos@gmail.com>
Date: Fri, 26 Jul 2024 12:35:43 -0700
Subject: [PATCH 2/7] accept compiler result before notifying caller

This is needed because the caller might call testTimeRecorder.print before this method got a chance to call testTimeRecorder.stop
---
 packages/flutter_tools/lib/src/test/test_compiler.dart | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/flutter_tools/lib/src/test/test_compiler.dart b/packages/flutter_tools/lib/src/test/test_compiler.dart
index a94688e9852bb..e1ac7d8e5c3a2 100644
--- a/packages/flutter_tools/lib/src/test/test_compiler.dart
+++ b/packages/flutter_tools/lib/src/test/test_compiler.dart
@@ -188,9 +188,11 @@ class TestCompiler {
       // compiler to avoid reusing compiler that might have gotten into
       // a weird state.
       if (outputPath == null || compilerOutput!.errorCount > 0) {
-        request.result.complete();
         await _shutdown();
+        request.result.complete();
       } else {
+        await compiler!.accept();
+        await compiler!.reset();
         if (shouldCopyDillFile) {
           final String path = request.mainUri.toFilePath(windows: globals.platform.isWindows);
           final File outputFile = globals.fs.file(outputPath);
@@ -209,8 +211,6 @@ class TestCompiler {
         } else {
           request.result.complete(outputPath);
         }
-        await compiler!.accept();
-        await compiler!.reset();
       }
       globals.printTrace('Compiling ${request.mainUri} took ${compilerTime.elapsedMilliseconds}ms');
       testTimeRecorder?.stop(TestTimePhases.Compile, testTimeRecorderStopwatch!);

From 755062196a92dc49b041209e0b8d0d3b95de82e7 Mon Sep 17 00:00:00 2001
From: Andrew Kolos <andrewrkolos@gmail.com>
Date: Fri, 26 Jul 2024 12:43:03 -0700
Subject: [PATCH 3/7] =?UTF-8?q?add=20more=20`await=20null`'s=20to=20`DevFS?=
 =?UTF-8?q?::update`=20=F0=9F=99=83?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 packages/flutter_tools/lib/src/devfs.dart | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/packages/flutter_tools/lib/src/devfs.dart b/packages/flutter_tools/lib/src/devfs.dart
index 33b6339d647e7..f5f4ed3517d9d 100644
--- a/packages/flutter_tools/lib/src/devfs.dart
+++ b/packages/flutter_tools/lib/src/devfs.dart
@@ -614,6 +614,12 @@ class DevFS {
       // before processing bundle.
       _logger.printTrace('Processing bundle.');
       // await null to give time for telling the compiler to compile.
+      // TODO(andrewkolos): This is a hack. Adding any more awaits to the compiler's
+      //  recompile method will cause this to be insufficent.
+      //  https://github.com/flutter/flutter/issues/151255.
+      await null;
+      await null;
+      await null;
       await null;
 
       // The tool writes the assets into the AssetBundle working dir so that they

From b6c6c38afc900bce8cfdd9f05faa34b5bc60296b Mon Sep 17 00:00:00 2001
From: Andrew Kolos <andrewrkolos@gmail.com>
Date: Fri, 26 Jul 2024 11:00:11 -0700
Subject: [PATCH 4/7] use pool

---
 packages/flutter_tools/lib/src/compile.dart | 23 ++++++++++++---------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/packages/flutter_tools/lib/src/compile.dart b/packages/flutter_tools/lib/src/compile.dart
index 4cb61033ed2b0..0092365a1cb07 100644
--- a/packages/flutter_tools/lib/src/compile.dart
+++ b/packages/flutter_tools/lib/src/compile.dart
@@ -7,6 +7,7 @@ import 'dart:typed_data';
 
 import 'package:meta/meta.dart';
 import 'package:package_config/package_config.dart';
+import 'package:pool/pool.dart';
 import 'package:process/process.dart';
 import 'package:usage/uuid/uuid.dart';
 
@@ -1063,24 +1064,26 @@ class DefaultResidentCompiler implements ResidentCompiler {
   Future<void> _writelnToServerStdin(String line, {
     bool printTrace = false,
   }) async {
-    final Process? server = _server;
-    if (server == null) {
-      return;
-    }
-    await ProcessUtils.writelnToStdinUnsafe(stdin: server.stdin, line: line);
-    if (printTrace) {
-      _logger.printTrace('<- $line');
-    }
+    await _writelnToServerStdinAll(<String>[line], printTrace: printTrace);
   }
 
-  Future<void> _writelnToServerStdinAll(List<String>? lines) async {
+  // TODO dont merge; explain why this is needed
+  final Pool _serverWritePool = Pool(1);
+  Future<void> _writelnToServerStdinAll(List<String> lines, {
+    bool printTrace = false,
+  }) async {
     final Process? server = _server;
     if (server == null) {
       return;
     }
-    for (final String line in lines ?? <String>[]) {
+    final PoolResource request = await _serverWritePool.request();
+    for (final String line in lines) {
       await ProcessUtils.writelnToStdinUnsafe(stdin: server.stdin, line: line);
+      if (printTrace) {
+        _logger.printTrace('<- $line');
+      }
     }
+    request.release();
   }
 }
 

From 648567c8accb3ddb98cbbd5f8fbc23a2f948c6a7 Mon Sep 17 00:00:00 2001
From: Andrew Kolos <andrewrkolos@gmail.com>
Date: Tue, 30 Jul 2024 13:36:41 -0700
Subject: [PATCH 5/7] add TODO about serializing writes

---
 .../flutter_tools/lib/src/base/process.dart   | 13 +++++++++--
 packages/flutter_tools/lib/src/compile.dart   | 23 ++++++++++++-------
 2 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/packages/flutter_tools/lib/src/base/process.dart b/packages/flutter_tools/lib/src/base/process.dart
index 96df867826736..6ce3f57b45252 100644
--- a/packages/flutter_tools/lib/src/base/process.dart
+++ b/packages/flutter_tools/lib/src/base/process.dart
@@ -228,8 +228,11 @@ abstract class ProcessUtils {
 
   /// Write [line] to [stdin] and catch any errors with [onError].
   ///
-  /// Specifically with [Process] file descriptors, an exception that is
-  /// thrown as part of a write can be most reliably caught with a
+  /// Concurrent calls to this method will result in an exception due to its
+  /// dependence on [IOSink.flush] (see https://github.com/dart-lang/sdk/issues/25277).
+  ///
+  /// Context: specifically with [Process] file descriptors, an exception that
+  /// is thrown as part of a write can be most reliably caught with a
   /// [ZoneSpecification] error handler.
   ///
   /// On some platforms, the following code appears to work:
@@ -278,6 +281,9 @@ abstract class ProcessUtils {
     );
   }
 
+  /// See [writelnToStdinGuarded].
+  ///
+  /// In the event that the write or flush fails, this will throw an Exception.
   static Future<void> writelnToStdinUnsafe({
     required IOSink stdin,
     required String line,
@@ -289,6 +295,9 @@ abstract class ProcessUtils {
     );
   }
 
+  /// See [writeToStdinGuarded].
+  ///
+  /// In the event that the write or flush fails, this will throw an Exception.
   static Future<void> writeToStdinUnsafe({
     required IOSink stdin,
     required String content,
diff --git a/packages/flutter_tools/lib/src/compile.dart b/packages/flutter_tools/lib/src/compile.dart
index 0092365a1cb07..7e1dc89b896c8 100644
--- a/packages/flutter_tools/lib/src/compile.dart
+++ b/packages/flutter_tools/lib/src/compile.dart
@@ -1067,8 +1067,12 @@ class DefaultResidentCompiler implements ResidentCompiler {
     await _writelnToServerStdinAll(<String>[line], printTrace: printTrace);
   }
 
-  // TODO dont merge; explain why this is needed
-  final Pool _serverWritePool = Pool(1);
+  // TODO(andrewkolos): Concurrent calls to ProcessUtils.writelnToStdinUnsafe
+  //  against the same stdin will result in an exception. To guard against this,
+  //  we need to force calls to run serially. Ideally, this wouldn't be
+  //  necessary since we shouldn't have multiple concurrent writes to the
+  //  compiler process. However, we do (https://github.com/flutter/flutter/issues/152577).
+  final Pool _serverStdinWritePool = Pool(1);
   Future<void> _writelnToServerStdinAll(List<String> lines, {
     bool printTrace = false,
   }) async {
@@ -1076,14 +1080,17 @@ class DefaultResidentCompiler implements ResidentCompiler {
     if (server == null) {
       return;
     }
-    final PoolResource request = await _serverWritePool.request();
-    for (final String line in lines) {
-      await ProcessUtils.writelnToStdinUnsafe(stdin: server.stdin, line: line);
-      if (printTrace) {
-        _logger.printTrace('<- $line');
+    final PoolResource request = await _serverStdinWritePool.request();
+    try {
+      for (final String line in lines) {
+        await ProcessUtils.writelnToStdinUnsafe(stdin: server.stdin, line: line);
+        if (printTrace) {
+          _logger.printTrace('<- $line');
+        }
       }
+    } finally {
+      request.release();
     }
-    request.release();
   }
 }
 

From e5273a843581089ca281d62da1cdae3f2b4afe4a Mon Sep 17 00:00:00 2001
From: Andrew Kolos <andrewrkolos@gmail.com>
Date: Tue, 30 Jul 2024 14:53:21 -0700
Subject: [PATCH 6/7] tweak doc strings

---
 packages/flutter_tools/lib/src/base/process.dart | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/packages/flutter_tools/lib/src/base/process.dart b/packages/flutter_tools/lib/src/base/process.dart
index 6ce3f57b45252..0ae0a3f60156c 100644
--- a/packages/flutter_tools/lib/src/base/process.dart
+++ b/packages/flutter_tools/lib/src/base/process.dart
@@ -283,7 +283,8 @@ abstract class ProcessUtils {
 
   /// See [writelnToStdinGuarded].
   ///
-  /// In the event that the write or flush fails, this will throw an Exception.
+  /// In the event that the write or flush fails, this will throw an exception
+  /// that preserves the stack trace of the callsite.
   static Future<void> writelnToStdinUnsafe({
     required IOSink stdin,
     required String line,
@@ -297,7 +298,8 @@ abstract class ProcessUtils {
 
   /// See [writeToStdinGuarded].
   ///
-  /// In the event that the write or flush fails, this will throw an Exception.
+  /// In the event that the write or flush fails, this will throw an exception
+  /// that preserves the stack trace of the callsite.
   static Future<void> writeToStdinUnsafe({
     required IOSink stdin,
     required String content,

From 27d8c3c058671541d7b6b392ae4855be85eb3912 Mon Sep 17 00:00:00 2001
From: Andrew Kolos <andrewrkolos@gmail.com>
Date: Mon, 5 Aug 2024 14:31:31 -0700
Subject: [PATCH 7/7] experiment: avoid asynchronous suspensions where
 convenient

---
 packages/flutter_tools/lib/src/compile.dart | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/packages/flutter_tools/lib/src/compile.dart b/packages/flutter_tools/lib/src/compile.dart
index 7e1dc89b896c8..c575ca795684f 100644
--- a/packages/flutter_tools/lib/src/compile.dart
+++ b/packages/flutter_tools/lib/src/compile.dart
@@ -1071,7 +1071,8 @@ class DefaultResidentCompiler implements ResidentCompiler {
   //  against the same stdin will result in an exception. To guard against this,
   //  we need to force calls to run serially. Ideally, this wouldn't be
   //  necessary since we shouldn't have multiple concurrent writes to the
-  //  compiler process. However, we do (https://github.com/flutter/flutter/issues/152577).
+  //  compiler process.
+  //  However, we do. See https://github.com/flutter/flutter/issues/152577.
   final Pool _serverStdinWritePool = Pool(1);
   Future<void> _writelnToServerStdinAll(List<String> lines, {
     bool printTrace = false,
@@ -1082,8 +1083,12 @@ class DefaultResidentCompiler implements ResidentCompiler {
     }
     final PoolResource request = await _serverStdinWritePool.request();
     try {
+      await ProcessUtils.writelnToStdinUnsafe(
+        stdin: server.stdin,
+        line: lines.join('\n'),
+      );
+
       for (final String line in lines) {
-        await ProcessUtils.writelnToStdinUnsafe(stdin: server.stdin, line: line);
         if (printTrace) {
           _logger.printTrace('<- $line');
         }

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