pkg/front_end/test/flutter_gallery_leak_tester.dart - sdk.git - Git at Google

 // Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 import 'dart:math';

 import "vm_service_heap_helper.dart" as helper;

 Completer completer;

 Set<String> files = {};

 // General idea: Do the once-a-week leak testing script
 // => In this file:
 //    * Start the frontend_server
 //    * Do a compilation
 //    * Pause the VM and do a "leak iteration"
 //    * Once the VM has been unpaused, do an invalidation etc and repeat.
 //
 // This script also makes sure to clone flutter gallery,
 // but assumes that flutter has been setup as by the script
 // `tools/bots/flutter/compile_flutter.sh`.

 main(List<String> args) async {
   if (Platform.isWindows) {
     throw "This script cannot run on Windows as it uses non-Windows "
         "assumptions both for the placement of pub packages and the presence "
         "of 'ln' for symbolic links. It has only been tested on Linux but will "
         "probably also work on Mac.";
   }

   bool quicker = false;
   bool alternativeInvalidation = false;
   String rootPath;

   for (String arg in args) {
     if (arg == "--quicker") {
       quicker = true;
     } else if (arg == "--alternativeInvalidation") {
       alternativeInvalidation = true;
     } else if (arg.startsWith("--path=")) {
       rootPath = arg.substring("--path=".length);
     } else {
       throw "Unknown argument '$arg'";
     }
   }

   if (rootPath == null) {
     throw "No path given. Pass with --path=<path>";
   }

   Directory patchedSdk = new Directory("$rootPath/flutter_patched_sdk/");
   if (!patchedSdk.existsSync()) {
     throw "Directory $patchedSdk doesn't exist.";
   }
   Uri frontendServerStarter = Platform.script
       .resolve("../../frontend_server/bin/frontend_server_starter.dart");
   if (!new File.fromUri(frontendServerStarter).existsSync()) {
     throw "File not found: $frontendServerStarter";
   }

   Directory gallery = new Directory("$rootPath/gallery");
   if (!gallery.existsSync()) {
     print("Gallery not found... Attempting to clone via git.");
     // git clone https://github.com/flutter/gallery.git
     Process process = await Process.start("git", [
       "clone",
       "https://github.com/flutter/gallery.git",
       "$rootPath/gallery"
     ]);
     process.stdout
         .transform(utf8.decoder)
         .transform(new LineSplitter())
         .listen((line) {
       print("git stdout> $line");
     });
     process.stderr
         .transform(utf8.decoder)
         .transform(new LineSplitter())
         .listen((line) {
       print("git stderr> $line");
     });
     int processExitCode = await process.exitCode;
     print("Exit code from git: $processExitCode");

     process = await Process.start("../flutter/bin/flutter", ["pub", "get"],
         workingDirectory: "$rootPath/gallery/");
     process.stdout
         .transform(utf8.decoder)
         .transform(new LineSplitter())
         .listen((line) {
       print("flutter stdout> $line");
     });
     process.stderr
         .transform(utf8.decoder)
         .transform(new LineSplitter())
         .listen((line) {
       print("flutter stderr> $line");
     });
     processExitCode = await process.exitCode;
     print("Exit code from flutter: $processExitCode");

     // Attempt to hack around strings being truncated to 128 bytes in heap dumps
     // https://github.com/dart-lang/sdk/blob/c59cdee365b94ce066344840f9e3412d642019b5/runtime/vm/object_graph.cc#L809
     // (pub paths can become too long, so two distinct files will look to have
     // the same url and thus give a false positive).
     Uri pubDirUri = Uri.parse("file://${Platform.environment['HOME']}/"
         ".pub-cache/hosted/pub.dartlang.org/");
     Directory pubDir = new Directory.fromUri(pubDirUri);
     if (!pubDir.existsSync()) throw "Expected to find $pubDir";
     File galleryDotPackages = new File("$rootPath/gallery/.packages");
     if (!galleryDotPackages.existsSync()) {
       throw "Didn't find $galleryDotPackages";
     }
     String data = galleryDotPackages.readAsStringSync();
     data = data.replaceAll(pubDirUri.toString(), "pub/");
     galleryDotPackages.writeAsStringSync(data);

     File galleryPackageConfig =
         new File("$rootPath/gallery/.dart_tool/package_config.json");
     if (!galleryPackageConfig.existsSync()) {
       throw "Didn't find $galleryPackageConfig";
     }
     data = galleryPackageConfig.readAsStringSync();
     data = data.replaceAll(pubDirUri.toString(), "../pub/");
     galleryPackageConfig.writeAsStringSync(data);

     process = await Process.start("ln", ["-s", pubDir.path, "pub"],
         workingDirectory: "$rootPath/gallery/");
     process.stdout
         .transform(utf8.decoder)
         .transform(new LineSplitter())
         .listen((line) {
       print("ln stdout> $line");
     });
     process.stderr
         .transform(utf8.decoder)
         .transform(new LineSplitter())
         .listen((line) {
       print("ln stderr> $line");
     });
     processExitCode = await process.exitCode;
     print("Exit code from ln: $processExitCode");
   }

   File galleryDotPackages = new File("$rootPath/gallery/.packages");
   if (!galleryDotPackages.existsSync()) {
     throw "Didn't find $galleryDotPackages";
   }

   List<helper.Interest> interests = new List<helper.Interest>();
   interests.add(new helper.Interest(
       Uri.parse("package:kernel/ast.dart"), "Library", ["fileUri"]));
   helper.VMServiceHeapHelperSpecificExactLeakFinder heapHelper =
       new helper.VMServiceHeapHelperSpecificExactLeakFinder(
           interests,
           [
             new helper.Interest(Uri.parse("package:kernel/ast.dart"), "Library",
                 ["fileUri", "_libraryIdString"]),
           ],
           true,
           false);

   print("About to run with "
       "quicker = $quicker; "
       "alternativeInvalidation = $alternativeInvalidation; "
       "path = $rootPath; "
       "...");

   List<String> processArgs = [
     "--disable_dart_dev",
     "--disable-service-auth-codes",
     frontendServerStarter.toString(),
     "--sdk-root",
     "$rootPath/flutter_patched_sdk/",
     "--incremental",
     "--target=flutter",
     "--debugger-module-names",
     "-Ddart.developer.causal_async_stacks=true",
     "--output-dill",
     "$rootPath/flutter_server_tmp.dill",
     "--packages",
     "$rootPath/gallery/.packages",
     "-Ddart.vm.profile=false",
     "-Ddart.vm.product=false",
     "--bytecode-options=source-positions,local-var-info,debugger-stops,"
         "instance-field-initializers,keep-unreachable-code,"
         "avoid-closure-call-instructions",
     "--enable-asserts",
     "--track-widget-creation",
     "--initialize-from-dill",
     "$rootPath/cache.dill",
   ];
   if (alternativeInvalidation) {
     processArgs.add("--enable-experiment=alternative-invalidation-strategy");
   }

   await heapHelper.start(processArgs,
       stdinReceiver: (s) {
         if (s.startsWith("+")) {
           files.add(s.substring(1));
         } else if (s.startsWith("-")) {
           files.remove(s.substring(1));
         } else {
           List<String> split = s.split(" ");
           if (int.tryParse(split.last) != null &&
               split[split.length - 2].endsWith(".dill")) {
             // e.g. something like "filename.dill 0" for output file and 0
             // errors.
             completer.complete();
           } else {
             print("out> $s");
           }
         }
       },
       stderrReceiver: (s) => print("err> $s"));

   await sendAndWait(heapHelper.process, ['compile package:gallery/main.dart']);
   Stopwatch stopwatch = new Stopwatch()..start();
   await pauseAndWait(heapHelper);
   print("First compile took ${stopwatch.elapsedMilliseconds} ms");

   await recompileAndWait(heapHelper.process, "package:gallery/main.dart", []);
   await accept(heapHelper);
   await sendAndWaitSetSelection(heapHelper.process);
   await sendAndWaitToObjectForSourceLocation(heapHelper.process);
   await sendAndWaitToObject(heapHelper.process);
   await pauseAndWait(heapHelper);

   print("Knows about ${files.length} files...");
   List<String> listFiles = new List<String>.from(files);
   int iteration = 0;
   for (String s in listFiles) {
     print("On iteration ${iteration++} / ${listFiles.length}");
     print(" => Invalidating $s");
     stopwatch.reset();
     await recompileAndWait(
         heapHelper.process, "package:gallery/main.dart", [s]);
     await accept(heapHelper);
     print("Recompile took ${stopwatch.elapsedMilliseconds} ms");
     await sendAndWaitSetSelection(heapHelper.process);
     await sendAndWaitToObjectForSourceLocation(heapHelper.process);
     await sendAndWaitToObject(heapHelper.process);
     if (quicker) {
       if (iteration % 10 == 0) {
         await pauseAndWait(heapHelper);
       }
     } else {
       await pauseAndWait(heapHelper);
     }
   }
   if (quicker) {
     await pauseAndWait(heapHelper);
   }

   // We should now be done.
   print("Done!");
   heapHelper.process.kill();
 }

 Future accept(
     helper.VMServiceHeapHelperSpecificExactLeakFinder heapHelper) async {
   heapHelper.process.stdin.writeln('accept');
   int waits = 0;
   while (!await heapHelper.isIdle()) {
     if (waits > 100) {
       // Waited for at least 10 seconds --- assume there's something wrong.
       throw "Timed out waiting to become idle!";
     }
     await new Future.delayed(new Duration(milliseconds: 100));
     waits++;
   }
 }

 class Uuid {
   final Random _random = new Random();

   /// Generate a version 4 (random) uuid. This is a uuid scheme that only uses
   /// random numbers as the source of the generated uuid.
   String generateV4() {
     // Generate xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx / 8-4-4-4-12.
     int special = 8 + _random.nextInt(4);

     return '${_bitsDigits(16, 4)}${_bitsDigits(16, 4)}-'
         '${_bitsDigits(16, 4)}-'
         '4${_bitsDigits(12, 3)}-'
         '${_printDigits(special, 1)}${_bitsDigits(12, 3)}-'
         '${_bitsDigits(16, 4)}${_bitsDigits(16, 4)}${_bitsDigits(16, 4)}';
   }

   String _bitsDigits(int bitCount, int digitCount) =>
       _printDigits(_generateBits(bitCount), digitCount);

   int _generateBits(int bitCount) => _random.nextInt(1 << bitCount);

   String _printDigits(int value, int count) =>
       value.toRadixString(16).padLeft(count, '0');
 }

 Future pauseAndWait(
     helper.VMServiceHeapHelperSpecificExactLeakFinder heapHelper) async {
   int prevIterationNumber = heapHelper.iterationNumber;
   await heapHelper.pause();

   int waits = 0;
   while (heapHelper.iterationNumber == prevIterationNumber) {
     if (waits > 10000) {
       // Waited for at least 1000 seconds --- assume there's something wrong.
       throw "Timed out waiting for the helper iteration number to increase!";
     }
     await new Future.delayed(new Duration(milliseconds: 100));
     waits++;
   }
 }

 Future recompileAndWait(
     Process _server, String what, List<String> invalidates) async {
   String inputKey = Uuid().generateV4();
   List<String> data = ['recompile $what $inputKey'];
   invalidates.forEach(data.add);
   data.add('$inputKey');
   await sendAndWait(_server, data);
 }

 Future sendAndWait(Process _server, List<String> data) async {
   completer = new Completer();
   data.forEach(_server.stdin.writeln);
   await completer.future;
 }

 Future sendAndWaitDebugDidSendFirstFrameEvent(Process _server) async {
   String inputKey = Uuid().generateV4();
   await sendAndWait(_server, [
     /* 'compile-expression' <boundarykey> */ 'compile-expression $inputKey',
     /* expression */ 'WidgetsBinding.instance.debugDidSendFirstFrameEvent',
     /* no definitions */
     /* <boundarykey> */ inputKey,
     /* no type-defintions */
     /* <boundarykey> */ inputKey,
     /* libraryUri */ 'package:flutter/src/widgets/binding.dart',
     /* class */ '',
     /* isStatic */ 'true'
   ]);
 }

 Future sendAndWaitSetSelection(Process _server) async {
   String inputKey = Uuid().generateV4();
   await sendAndWait(_server, [
     /* 'compile-expression' <boundarykey> */ 'compile-expression $inputKey',
     /* expression */ 'WidgetInspectorService.instance.setSelection('
         'arg1, "dummy_68")',
     /* definition #1 */ 'arg1',
     /* <boundarykey> */ inputKey,
     /* no type-defintions */
     /* <boundarykey> */ inputKey,
     /* libraryUri */ 'package:flutter/src/widgets/widget_inspector.dart',
     /* class */ '',
     /* isStatic */ 'true'
   ]);
 }

 Future sendAndWaitToObject(Process _server) async {
   String inputKey = Uuid().generateV4();
   await sendAndWait(_server, [
     /* 'compile-expression' <boundarykey> */ 'compile-expression $inputKey',
     /* expression */ 'WidgetInspectorService.instance.toObject('
         '"inspector-836", "tree_112")',
     /* no definitions */
     /* <boundarykey> */ inputKey,
     /* no type-defintions */
     /* <boundarykey> */ inputKey,
     /* libraryUri */ 'package:flutter/src/widgets/widget_inspector.dart',
     /* class */ '',
     /* isStatic */ 'true'
   ]);
 }

 Future sendAndWaitToObjectForSourceLocation(Process _server) async {
   String inputKey = Uuid().generateV4();
   await sendAndWait(_server, [
     /* 'compile-expression' <boundarykey> */ 'compile-expression $inputKey',
     /* expression */ 'WidgetInspectorService.instance.'
         'toObjectForSourceLocation("inspector-607", "tree_112")',
     /* no definitions */
     /* <boundarykey> */ inputKey,
     /* no type-defintions */
     /* <boundarykey> */ inputKey,
     /* libraryUri */ 'package:flutter/src/widgets/widget_inspector.dart',
     /* class */ '',
     /* isStatic */ 'true'
   ]);
 }
	// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	import 'dart:async';
	import 'dart:convert';
	import 'dart:io';
	import 'dart:math';

	import "vm_service_heap_helper.dart" as helper;

	Completer completer;

	Set<String> files = {};

	// General idea: Do the once-a-week leak testing script
	// => In this file:
	// * Start the frontend_server
	// * Do a compilation
	// * Pause the VM and do a "leak iteration"
	// * Once the VM has been unpaused, do an invalidation etc and repeat.
	//
	// This script also makes sure to clone flutter gallery,
	// but assumes that flutter has been setup as by the script
	// `tools/bots/flutter/compile_flutter.sh`.

	main(List<String> args) async {
	if (Platform.isWindows) {
	throw "This script cannot run on Windows as it uses non-Windows "
	"assumptions both for the placement of pub packages and the presence "
	"of 'ln' for symbolic links. It has only been tested on Linux but will "
	"probably also work on Mac.";
	}

	bool quicker = false;
	bool alternativeInvalidation = false;
	String rootPath;

	for (String arg in args) {
	if (arg == "--quicker") {
	quicker = true;
	} else if (arg == "--alternativeInvalidation") {
	alternativeInvalidation = true;
	} else if (arg.startsWith("--path=")) {
	rootPath = arg.substring("--path=".length);
	} else {
	throw "Unknown argument '$arg'";
	}
	}

	if (rootPath == null) {
	throw "No path given. Pass with --path=<path>";
	}

	Directory patchedSdk = new Directory("$rootPath/flutter_patched_sdk/");
	if (!patchedSdk.existsSync()) {
	throw "Directory $patchedSdk doesn't exist.";
	}
	Uri frontendServerStarter = Platform.script
	.resolve("../../frontend_server/bin/frontend_server_starter.dart");
	if (!new File.fromUri(frontendServerStarter).existsSync()) {
	throw "File not found: $frontendServerStarter";
	}

	Directory gallery = new Directory("$rootPath/gallery");
	if (!gallery.existsSync()) {
	print("Gallery not found... Attempting to clone via git.");
	// git clone https://github.com/flutter/gallery.git
	Process process = await Process.start("git", [
	"clone",
	"https://github.com/flutter/gallery.git",
	"$rootPath/gallery"
	]);
	process.stdout
	.transform(utf8.decoder)
	.transform(new LineSplitter())
	.listen((line) {
	print("git stdout> $line");
	});
	process.stderr
	.transform(utf8.decoder)
	.transform(new LineSplitter())
	.listen((line) {
	print("git stderr> $line");
	});
	int processExitCode = await process.exitCode;
	print("Exit code from git: $processExitCode");

	process = await Process.start("../flutter/bin/flutter", ["pub", "get"],
	workingDirectory: "$rootPath/gallery/");
	process.stdout
	.transform(utf8.decoder)
	.transform(new LineSplitter())
	.listen((line) {
	print("flutter stdout> $line");
	});
	process.stderr
	.transform(utf8.decoder)
	.transform(new LineSplitter())
	.listen((line) {
	print("flutter stderr> $line");
	});
	processExitCode = await process.exitCode;
	print("Exit code from flutter: $processExitCode");

	// Attempt to hack around strings being truncated to 128 bytes in heap dumps
	// https://github.com/dart-lang/sdk/blob/c59cdee365b94ce066344840f9e3412d642019b5/runtime/vm/object_graph.cc#L809
	// (pub paths can become too long, so two distinct files will look to have
	// the same url and thus give a false positive).
	Uri pubDirUri = Uri.parse("file://${Platform.environment['HOME']}/"
	".pub-cache/hosted/pub.dartlang.org/");
	Directory pubDir = new Directory.fromUri(pubDirUri);
	if (!pubDir.existsSync()) throw "Expected to find $pubDir";
	File galleryDotPackages = new File("$rootPath/gallery/.packages");
	if (!galleryDotPackages.existsSync()) {
	throw "Didn't find $galleryDotPackages";
	}
	String data = galleryDotPackages.readAsStringSync();
	data = data.replaceAll(pubDirUri.toString(), "pub/");
	galleryDotPackages.writeAsStringSync(data);

	File galleryPackageConfig =
	new File("$rootPath/gallery/.dart_tool/package_config.json");
	if (!galleryPackageConfig.existsSync()) {
	throw "Didn't find $galleryPackageConfig";
	}
	data = galleryPackageConfig.readAsStringSync();
	data = data.replaceAll(pubDirUri.toString(), "../pub/");
	galleryPackageConfig.writeAsStringSync(data);

	process = await Process.start("ln", ["-s", pubDir.path, "pub"],
	workingDirectory: "$rootPath/gallery/");
	process.stdout
	.transform(utf8.decoder)
	.transform(new LineSplitter())
	.listen((line) {
	print("ln stdout> $line");
	});
	process.stderr
	.transform(utf8.decoder)
	.transform(new LineSplitter())
	.listen((line) {
	print("ln stderr> $line");
	});
	processExitCode = await process.exitCode;
	print("Exit code from ln: $processExitCode");
	}

	File galleryDotPackages = new File("$rootPath/gallery/.packages");
	if (!galleryDotPackages.existsSync()) {
	throw "Didn't find $galleryDotPackages";
	}

	List<helper.Interest> interests = new List<helper.Interest>();
	interests.add(new helper.Interest(
	Uri.parse("package:kernel/ast.dart"), "Library", ["fileUri"]));
	helper.VMServiceHeapHelperSpecificExactLeakFinder heapHelper =
	new helper.VMServiceHeapHelperSpecificExactLeakFinder(
	interests,
	[
	new helper.Interest(Uri.parse("package:kernel/ast.dart"), "Library",
	["fileUri", "_libraryIdString"]),
	],
	true,
	false);

	print("About to run with "
	"quicker = $quicker; "
	"alternativeInvalidation = $alternativeInvalidation; "
	"path = $rootPath; "
	"...");

	List<String> processArgs = [
	"--disable_dart_dev",
	"--disable-service-auth-codes",
	frontendServerStarter.toString(),
	"--sdk-root",
	"$rootPath/flutter_patched_sdk/",
	"--incremental",
	"--target=flutter",
	"--debugger-module-names",
	"-Ddart.developer.causal_async_stacks=true",
	"--output-dill",
	"$rootPath/flutter_server_tmp.dill",
	"--packages",
	"$rootPath/gallery/.packages",
	"-Ddart.vm.profile=false",
	"-Ddart.vm.product=false",
	"--bytecode-options=source-positions,local-var-info,debugger-stops,"
	"instance-field-initializers,keep-unreachable-code,"
	"avoid-closure-call-instructions",
	"--enable-asserts",
	"--track-widget-creation",
	"--initialize-from-dill",
	"$rootPath/cache.dill",
	];
	if (alternativeInvalidation) {
	processArgs.add("--enable-experiment=alternative-invalidation-strategy");
	}

	await heapHelper.start(processArgs,
	stdinReceiver: (s) {
	if (s.startsWith("+")) {
	files.add(s.substring(1));
	} else if (s.startsWith("-")) {
	files.remove(s.substring(1));
	} else {
	List<String> split = s.split(" ");
	if (int.tryParse(split.last) != null &&
	split[split.length - 2].endsWith(".dill")) {
	// e.g. something like "filename.dill 0" for output file and 0
	// errors.
	completer.complete();
	} else {
	print("out> $s");
	}
	}
	},
	stderrReceiver: (s) => print("err> $s"));

	await sendAndWait(heapHelper.process, ['compile package:gallery/main.dart']);
	Stopwatch stopwatch = new Stopwatch()..start();
	await pauseAndWait(heapHelper);
	print("First compile took ${stopwatch.elapsedMilliseconds} ms");

	await recompileAndWait(heapHelper.process, "package:gallery/main.dart", []);
	await accept(heapHelper);
	await sendAndWaitSetSelection(heapHelper.process);
	await sendAndWaitToObjectForSourceLocation(heapHelper.process);
	await sendAndWaitToObject(heapHelper.process);
	await pauseAndWait(heapHelper);

	print("Knows about ${files.length} files...");
	List<String> listFiles = new List<String>.from(files);
	int iteration = 0;
	for (String s in listFiles) {
	print("On iteration ${iteration++} / ${listFiles.length}");
	print(" => Invalidating $s");
	stopwatch.reset();
	await recompileAndWait(
	heapHelper.process, "package:gallery/main.dart", [s]);
	await accept(heapHelper);
	print("Recompile took ${stopwatch.elapsedMilliseconds} ms");
	await sendAndWaitSetSelection(heapHelper.process);
	await sendAndWaitToObjectForSourceLocation(heapHelper.process);
	await sendAndWaitToObject(heapHelper.process);
	if (quicker) {
	if (iteration % 10 == 0) {
	await pauseAndWait(heapHelper);
	}
	} else {
	await pauseAndWait(heapHelper);
	}
	}
	if (quicker) {
	await pauseAndWait(heapHelper);
	}

	// We should now be done.
	print("Done!");
	heapHelper.process.kill();
	}

	Future accept(
	helper.VMServiceHeapHelperSpecificExactLeakFinder heapHelper) async {
	heapHelper.process.stdin.writeln('accept');
	int waits = 0;
	while (!await heapHelper.isIdle()) {
	if (waits > 100) {
	// Waited for at least 10 seconds --- assume there's something wrong.
	throw "Timed out waiting to become idle!";
	}
	await new Future.delayed(new Duration(milliseconds: 100));
	waits++;
	}
	}

	class Uuid {
	final Random _random = new Random();

	/// Generate a version 4 (random) uuid. This is a uuid scheme that only uses
	/// random numbers as the source of the generated uuid.
	String generateV4() {
	// Generate xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx / 8-4-4-4-12.
	int special = 8 + _random.nextInt(4);

	return '${_bitsDigits(16, 4)}${_bitsDigits(16, 4)}-'
	'${_bitsDigits(16, 4)}-'
	'4${_bitsDigits(12, 3)}-'
	'${_printDigits(special, 1)}${_bitsDigits(12, 3)}-'
	'${_bitsDigits(16, 4)}${_bitsDigits(16, 4)}${_bitsDigits(16, 4)}';
	}

	String _bitsDigits(int bitCount, int digitCount) =>
	_printDigits(_generateBits(bitCount), digitCount);

	int _generateBits(int bitCount) => _random.nextInt(1 << bitCount);

	String _printDigits(int value, int count) =>
	value.toRadixString(16).padLeft(count, '0');
	}

	Future pauseAndWait(
	helper.VMServiceHeapHelperSpecificExactLeakFinder heapHelper) async {
	int prevIterationNumber = heapHelper.iterationNumber;
	await heapHelper.pause();

	int waits = 0;
	while (heapHelper.iterationNumber == prevIterationNumber) {
	if (waits > 10000) {
	// Waited for at least 1000 seconds --- assume there's something wrong.
	throw "Timed out waiting for the helper iteration number to increase!";
	}
	await new Future.delayed(new Duration(milliseconds: 100));
	waits++;
	}
	}

	Future recompileAndWait(
	Process _server, String what, List<String> invalidates) async {
	String inputKey = Uuid().generateV4();
	List<String> data = ['recompile $what $inputKey'];
	invalidates.forEach(data.add);
	data.add('$inputKey');
	await sendAndWait(_server, data);
	}

	Future sendAndWait(Process _server, List<String> data) async {
	completer = new Completer();
	data.forEach(_server.stdin.writeln);
	await completer.future;
	}

	Future sendAndWaitDebugDidSendFirstFrameEvent(Process _server) async {
	String inputKey = Uuid().generateV4();
	await sendAndWait(_server, [
	/* 'compile-expression' <boundarykey> */ 'compile-expression $inputKey',
	/* expression */ 'WidgetsBinding.instance.debugDidSendFirstFrameEvent',
	/* no definitions */
	/* <boundarykey> */ inputKey,
	/* no type-defintions */
	/* <boundarykey> */ inputKey,
	/* libraryUri */ 'package:flutter/src/widgets/binding.dart',
	/* class */ '',
	/* isStatic */ 'true'
	]);
	}

	Future sendAndWaitSetSelection(Process _server) async {
	String inputKey = Uuid().generateV4();
	await sendAndWait(_server, [
	/* 'compile-expression' <boundarykey> */ 'compile-expression $inputKey',
	/* expression */ 'WidgetInspectorService.instance.setSelection('
	'arg1, "dummy_68")',
	/* definition #1 */ 'arg1',
	/* <boundarykey> */ inputKey,
	/* no type-defintions */
	/* <boundarykey> */ inputKey,
	/* libraryUri */ 'package:flutter/src/widgets/widget_inspector.dart',
	/* class */ '',
	/* isStatic */ 'true'
	]);
	}

	Future sendAndWaitToObject(Process _server) async {
	String inputKey = Uuid().generateV4();
	await sendAndWait(_server, [
	/* 'compile-expression' <boundarykey> */ 'compile-expression $inputKey',
	/* expression */ 'WidgetInspectorService.instance.toObject('
	'"inspector-836", "tree_112")',
	/* no definitions */
	/* <boundarykey> */ inputKey,
	/* no type-defintions */
	/* <boundarykey> */ inputKey,
	/* libraryUri */ 'package:flutter/src/widgets/widget_inspector.dart',
	/* class */ '',
	/* isStatic */ 'true'
	]);
	}

	Future sendAndWaitToObjectForSourceLocation(Process _server) async {
	String inputKey = Uuid().generateV4();
	await sendAndWait(_server, [
	/* 'compile-expression' <boundarykey> */ 'compile-expression $inputKey',
	/* expression */ 'WidgetInspectorService.instance.'
	'toObjectForSourceLocation("inspector-607", "tree_112")',
	/* no definitions */
	/* <boundarykey> */ inputKey,
	/* no type-defintions */
	/* <boundarykey> */ inputKey,
	/* libraryUri */ 'package:flutter/src/widgets/widget_inspector.dart',
	/* class */ '',
	/* isStatic */ 'true'
	]);
	}