Cleaner test.dart output. (#109206)

dev/bots/flutter_compact_formatter.dart

-// Copyright 2014 The Flutter Authors. 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:convert';
-import 'dart:io';
-
-final Stopwatch _stopwatch = Stopwatch();
-
-/// A wrapper around package:test's JSON reporter.
-///
-/// This class behaves similarly to the compact reporter, but suppresses all
-/// output except for progress until the end of testing. In other words, errors,
-/// [print] calls, and skipped test messages will not be printed during the run
-/// of the suite.
-///
-/// It also processes the JSON data into a collection of [TestResult]s for any
-/// other post processing needs, e.g. sending data to analytics.
-class FlutterCompactFormatter {
-  FlutterCompactFormatter() {
-    _stopwatch.start();
-  }
-
-  /// Whether to use color escape codes in writing to stdout.
-  final bool useColor = stdout.supportsAnsiEscapes;
-
-  /// The terminal escape for green text, or the empty string if this is Windows
-  /// or not outputting to a terminal.
-  String get _green => useColor ? '\u001b[32m' : '';
-
-  /// The terminal escape for red text, or the empty string if this is Windows
-  /// or not outputting to a terminal.
-  String get _red => useColor ? '\u001b[31m' : '';
-
-  /// The terminal escape for yellow text, or the empty string if this is
-  /// Windows or not outputting to a terminal.
-  String get _yellow => useColor ? '\u001b[33m' : '';
-
-  /// The terminal escape for gray text, or the empty string if this is
-  /// Windows or not outputting to a terminal.
-  String get _gray => useColor ? '\u001b[1;30m' : '';
-
-  /// The terminal escape for bold text, or the empty string if this is
-  /// Windows or not outputting to a terminal.
-  String get _bold => useColor ? '\u001b[1m' : '';
-
-  /// The terminal escape for removing test coloring, or the empty string if
-  /// this is Windows or not outputting to a terminal.
-  String get _noColor => useColor ? '\u001b[0m' : '';
-
-  /// The terminal escape for clearing the line, or a carriage return if
-  /// this is Windows or not outputting to a terminal.
-  String get _clearLine => useColor ? '\x1b[2K\r' : '\r';
-
-  final Map<int, TestResult> _tests = <int, TestResult>{};
-
-  /// The test results from this run.
-  Iterable<TestResult> get tests => _tests.values;
-
-  /// The number of tests that were started.
-  int started = 0;
-
-  /// The number of test failures.
-  int failures = 0;
-
-  /// The number of skipped tests.
-  int skips = 0;
-
-  /// The number of successful tests.
-  int successes = 0;
-
-  /// Process a single line of JSON output from the JSON test reporter.
-  ///
-  /// Callers are responsible for splitting multiple lines before calling this
-  /// method.
-  TestResult? processRawOutput(String raw) {
-    assert(raw != null);
-    // We might be getting messages from Flutter Tool about updating/building.
-    if (!raw.startsWith('{')) {
-      print(raw);
-      return null;
-    }
-    final Map<String, dynamic> decoded = json.decode(raw) as Map<String, dynamic>;
-    final TestResult? originalResult = _tests[decoded['testID']];
-    switch (decoded['type'] as String) {
-      case 'done':
-        stdout.write(_clearLine);
-        stdout.write('$_bold${_stopwatch.elapsed}$_noColor ');
-        stdout.writeln(
-            '$_green+$successes $_yellow~$skips $_red-$failures:$_bold$_gray Done.$_noColor');
-        break;
-      case 'testStart':
-        final Map<String, dynamic> testData = decoded['test'] as Map<String, dynamic>;
-        if (testData['url'] == null) {
-          started += 1;
-          stdout.write(_clearLine);
-          stdout.write('$_bold${_stopwatch.elapsed}$_noColor ');
-          stdout.write(
-              '$_green+$successes $_yellow~$skips $_red-$failures: $_gray${testData['name']}$_noColor');
-          break;
-        }
-        _tests[testData['id'] as int] = TestResult(
-          id: testData['id'] as int,
-          name: testData['name'] as String,
-          line: testData['root_line'] as int? ?? testData['line'] as int,
-          column: testData['root_column'] as int? ?? testData['column'] as int,
-          path: testData['root_url'] as String? ?? testData['url'] as String,
-          startTime: decoded['time'] as int,
-        );
-        break;
-      case 'testDone':
-        if (originalResult == null) {
-          break;
-        }
-        originalResult.endTime = decoded['time'] as int;
-        if (decoded['skipped'] == true) {
-          skips += 1;
-          originalResult.status = TestStatus.skipped;
-        } else {
-          if (decoded['result'] == 'success') {
-            originalResult.status =TestStatus.succeeded;
-            successes += 1;
-          } else {
-            originalResult.status = TestStatus.failed;
-            failures += 1;
-          }
-        }
-        break;
-      case 'error':
-        final String error = decoded['error'] as String;
-        final String stackTrace = decoded['stackTrace'] as String;
-        if (originalResult != null) {
-          originalResult.errorMessage = error;
-          originalResult.stackTrace = stackTrace;
-        } else {
-          if (error != null) {
-            stderr.writeln(error);
-          }
-          if (stackTrace != null) {
-            stderr.writeln(stackTrace);
-          }
-        }
-        break;
-      case 'print':
-        if (originalResult != null) {
-          originalResult.messages.add(decoded['message'] as String);
-        }
-        break;
-      case 'group':
-      case 'allSuites':
-      case 'start':
-      case 'suite':
-      default:
-        break;
-    }
-    return originalResult;
-  }
-
-  /// Print summary of test results.
-  void finish() {
-    final List<String> skipped = <String>[];
-    final List<String> failed = <String>[];
-    for (final TestResult result in _tests.values) {
-      switch (result.status) {
-        case TestStatus.started:
-          failed.add('${_red}Unexpectedly failed to complete a test!');
-          failed.add(result.toString() + _noColor);
-          break;
-        case TestStatus.skipped:
-          skipped.add(
-              '${_yellow}Skipped ${result.name} (${result.pathLineColumn}).$_noColor');
-          break;
-        case TestStatus.failed:
-          failed.addAll(<String>[
-            '$_bold${_red}Failed ${result.name} (${result.pathLineColumn}):',
-            result.errorMessage!,
-            _noColor + _red,
-            result.stackTrace!,
-          ]);
-          failed.addAll(result.messages);
-          failed.add(_noColor);
-          break;
-        case TestStatus.succeeded:
-          break;
-      }
-    }
-    skipped.forEach(print);
-    failed.forEach(print);
-    if (failed.isEmpty) {
-      print('${_green}Completed, $successes test(s) passing ($skips skipped).$_noColor');
-    } else {
-      print('$_gray$failures test(s) failed.$_noColor');
-    }
-  }
-}
-
-/// The state of a test received from the JSON reporter.
-enum TestStatus {
-  /// Test execution has started.
-  started,
-  /// Test completed successfully.
-  succeeded,
-  /// Test failed.
-  failed,
-  /// Test was skipped.
-  skipped,
-}
-
-/// The detailed status of a test run.
-class TestResult {
-  TestResult({
-    required this.id,
-    required this.name,
-    required this.line,
-    required this.column,
-    required this.path,
-    required this.startTime,
-    this.status = TestStatus.started,
-  })  : assert(id != null),
-        assert(name != null),
-        assert(line != null),
-        assert(column != null),
-        assert(path != null),
-        assert(startTime != null),
-        assert(status != null),
-        messages = <String>[];
-
-  /// The state of the test.
-  TestStatus status;
-
-  /// The internal ID of the test used by the JSON reporter.
-  final int id;
-
-  /// The name of the test, specified via the `test` method.
-  final String name;
-
-  /// The line number from the original file.
-  final int line;
-
-  /// The column from the original file.
-  final int column;
-
-  /// The path of the original test file.
-  final String path;
-
-  /// A friendly print out of the [path], [line], and [column] of the test.
-  String get pathLineColumn => '$path:$line:$column';
-
-  /// The start time of the test, in milliseconds relative to suite startup.
-  final int startTime;
-
-  /// The stdout of the test.
-  final List<String> messages;
-
-  /// The error message from the test, from an `expect`, an [Exception] or
-  /// [Error].
-  String? errorMessage;
-
-  /// The stacktrace from a test failure.
-  String? stackTrace;
-
-  /// The time, in milliseconds relative to suite startup, that the test ended.
-  int? endTime;
-
-  /// The total time, in milliseconds, that the test took.
-  int get totalTime => (endTime ?? _stopwatch.elapsedMilliseconds) - startTime;
-
-  @override
-  String toString() => '{$runtimeType: {$id, $name, ${totalTime}ms, $pathLineColumn}}';
-}

dev/bots/run_command.dart

@@ -50,23 +50,9 @@ class Command {
 
   /// The raw process that was launched for this command.
   final io.Process process;
-
   final Stopwatch _time;
-  final Future<List<List<int>>>? _savedStdout;
-  final Future<List<List<int>>>? _savedStderr;
-
-  /// Evaluates when the [process] exits.
-  ///
-  /// Returns the result of running the command.
-  Future<CommandResult> get onExit async {
-    final int exitCode = await process.exitCode;
-    _time.stop();
-
-    // Saved output is null when OutputMode.print is used.
-    final String? flattenedStdout = _savedStdout != null ? _flattenToString((await _savedStdout)!) : null;
-    final String? flattenedStderr = _savedStderr != null ? _flattenToString((await _savedStderr)!) : null;
-    return CommandResult._(exitCode, _time.elapsed, flattenedStdout, flattenedStderr);
-  }
+  final Future<String> _savedStdout;
+  final Future<String> _savedStderr;
 }
 
 /// The result of running a command using [startCommand] and [runCommand];
@@ -105,46 +91,50 @@ Future<Command> startCommand(String executable, List<String> arguments, {
 }) async {
   final String commandDescription = '${path.relative(executable, from: workingDirectory)} ${arguments.join(' ')}';
   final String relativeWorkingDir = path.relative(workingDirectory ?? io.Directory.current.path);
-  printProgress('RUNNING', relativeWorkingDir, commandDescription);
+  print('RUNNING: cd $cyan$relativeWorkingDir$reset; $green$commandDescription$reset');
 
   final Stopwatch time = Stopwatch()..start();
   final io.Process process = await io.Process.start(executable, arguments,
     workingDirectory: workingDirectory,
     environment: environment,
   );
-
-  Future<List<List<int>>> savedStdout = Future<List<List<int>>>.value(<List<int>>[]);
-  Future<List<List<int>>> savedStderr = Future<List<List<int>>>.value(<List<int>>[]);
-  final Stream<List<int>> stdoutSource = process.stdout
-    .transform<String>(const Utf8Decoder())
-    .transform(const LineSplitter())
-    .where((String line) => removeLine == null || !removeLine(line))
-    .map((String line) {
-      final String formattedLine = '$line\n';
-      if (outputListener != null) {
-        outputListener(formattedLine, process);
-      }
-      return formattedLine;
-    })
-    .transform(const Utf8Encoder());
-  switch (outputMode) {
-    case OutputMode.print:
-      stdoutSource.listen((List<int> output) {
-        io.stdout.add(output);
-        savedStdout.then((List<List<int>> list) => list.add(output));
-      });
-      process.stderr.listen((List<int> output) {
-        io.stdout.add(output);
-        savedStdout.then((List<List<int>> list) => list.add(output));
-      });
-      break;
-    case OutputMode.capture:
-      savedStdout = stdoutSource.toList();
-      savedStderr = process.stderr.toList();
-      break;
-  }
-
-  return Command._(process, time, savedStdout, savedStderr);
+  return Command._(
+    process,
+    time,
+    process.stdout
+      .transform<String>(const Utf8Decoder())
+      .transform(const LineSplitter())
+      .where((String line) => removeLine == null || !removeLine(line))
+      .map<String>((String line) {
+        final String formattedLine = '$line\n';
+        if (outputListener != null) {
+          outputListener(formattedLine, process);
+        }
+        switch (outputMode) {
+          case OutputMode.print:
+            print(line);
+            break;
+          case OutputMode.capture:
+            break;
+        }
+        return line;
+      })
+      .join('\n'),
+    process.stderr
+      .transform<String>(const Utf8Decoder())
+      .transform(const LineSplitter())
+      .map<String>((String line) {
+        switch (outputMode) {
+          case OutputMode.print:
+            print(line);
+            break;
+          case OutputMode.capture:
+            break;
+        }
+        return line;
+      })
+      .join('\n'),
+  );
 }
 
 /// Runs the `executable` and waits until the process exits.
@@ -182,7 +172,12 @@ Future<CommandResult> runCommand(String executable, List<String> arguments, {
     outputListener: outputListener,
   );
 
-  final CommandResult result = await command.onExit;
+  final CommandResult result = CommandResult._(
+    await command.process.exitCode,
+    command._time.elapsed,
+    await command._savedStdout,
+    await command._savedStderr,
+  );
 
   if ((result.exitCode == 0) == expectNonZeroExit || (expectedExitCode != null && result.exitCode != expectedExitCode)) {
     // Print the output when we get unexpected results (unless output was
@@ -191,28 +186,24 @@ Future<CommandResult> runCommand(String executable, List<String> arguments, {
       case OutputMode.print:
         break;
       case OutputMode.capture:
-        io.stdout.writeln(result.flattenedStdout);
-        io.stdout.writeln(result.flattenedStderr);
+        print(result.flattenedStdout);
+        print(result.flattenedStderr);
         break;
     }
     foundError(<String>[
       if (failureMessage != null)
         failureMessage
       else
-        '${bold}ERROR: ${red}Last command exited with ${result.exitCode} (expected: ${expectNonZeroExit ? (expectedExitCode ?? 'non-zero') : 'zero'}).$reset',
+        '$bold${red}Command exited with exit code ${result.exitCode} but expected: ${expectNonZeroExit ? (expectedExitCode ?? 'non-zero') : 'zero'} exit code.$reset',
       '${bold}Command: $green$commandDescription$reset',
       '${bold}Relative working directory: $cyan$relativeWorkingDir$reset',
     ]);
   } else {
-    print('$clock ELAPSED TIME: ${prettyPrintDuration(result.elapsedTime)} for $green$commandDescription$reset in $cyan$relativeWorkingDir$reset');
+    print('ELAPSED TIME: ${prettyPrintDuration(result.elapsedTime)} for $green$commandDescription$reset in $cyan$relativeWorkingDir$reset');
   }
   return result;
 }
 
-/// Flattens a nested list of UTF-8 code units into a single string.
-String _flattenToString(List<List<int>> chunks) =>
-  utf8.decode(chunks.expand<int>((List<int> ints) => ints).toList());
-
 /// Specifies what to do with the command output from [runCommand] and [startCommand].
 enum OutputMode {
   /// Forwards standard output and standard error streams to the test process'

dev/bots/service_worker_test.dart

@@ -163,8 +163,8 @@ Future<void> runWebServiceWorkerTest({
   Future<void> startAppServer({
     required String cacheControl,
   }) async {
-    final int serverPort = await findAvailablePort();
-    final int browserDebugPort = await findAvailablePort();
+    final int serverPort = await findAvailablePortAndPossiblyCauseFlakyTests();
+    final int browserDebugPort = await findAvailablePortAndPossiblyCauseFlakyTests();
     server = await AppServer.start(
       headless: headless,
       cacheControl: cacheControl,
@@ -201,7 +201,7 @@ Future<void> runWebServiceWorkerTest({
 
   final bool shouldExpectFlutterJs = testType != ServiceWorkerTestType.withoutFlutterJs;
 
-  print('BEGIN runWebServiceWorkerTest(headless: $headless, testType: $testType)\n');
+  print('BEGIN runWebServiceWorkerTest(headless: $headless, testType: $testType)');
 
   try {
     /////
@@ -417,7 +417,7 @@ Future<void> runWebServiceWorkerTest({
     await server?.stop();
   }
 
-  print('END runWebServiceWorkerTest(headless: $headless, testType: $testType)\n');
+  print('END runWebServiceWorkerTest(headless: $headless, testType: $testType)');
 }
 
 Future<void> runWebServiceWorkerTestWithCachingResources({
@@ -435,8 +435,8 @@ Future<void> runWebServiceWorkerTestWithCachingResources({
   Future<void> startAppServer({
     required String cacheControl,
   }) async {
-    final int serverPort = await findAvailablePort();
-    final int browserDebugPort = await findAvailablePort();
+    final int serverPort = await findAvailablePortAndPossiblyCauseFlakyTests();
+    final int browserDebugPort = await findAvailablePortAndPossiblyCauseFlakyTests();
     server = await AppServer.start(
       headless: headless,
       cacheControl: cacheControl,
@@ -472,7 +472,7 @@ Future<void> runWebServiceWorkerTestWithCachingResources({
 
   final bool shouldExpectFlutterJs = testType != ServiceWorkerTestType.withoutFlutterJs;
 
-  print('BEGIN runWebServiceWorkerTestWithCachingResources(headless: $headless, testType: $testType)\n');
+  print('BEGIN runWebServiceWorkerTestWithCachingResources(headless: $headless, testType: $testType)');
 
   try {
     //////////////////////////////////////////////////////
@@ -576,7 +576,7 @@ Future<void> runWebServiceWorkerTestWithCachingResources({
     await server?.stop();
   }
 
-  print('END runWebServiceWorkerTestWithCachingResources(headless: $headless, testType: $testType)\n');
+  print('END runWebServiceWorkerTestWithCachingResources(headless: $headless, testType: $testType)');
 }
 
 Future<void> runWebServiceWorkerTestWithBlockedServiceWorkers({
@@ -593,8 +593,8 @@ Future<void> runWebServiceWorkerTestWithBlockedServiceWorkers({
   Future<void> startAppServer({
     required String cacheControl,
   }) async {
-    final int serverPort = await findAvailablePort();
-    final int browserDebugPort = await findAvailablePort();
+    final int serverPort = await findAvailablePortAndPossiblyCauseFlakyTests();
+    final int browserDebugPort = await findAvailablePortAndPossiblyCauseFlakyTests();
     server = await AppServer.start(
       headless: headless,
       cacheControl: cacheControl,
@@ -628,7 +628,7 @@ Future<void> runWebServiceWorkerTestWithBlockedServiceWorkers({
     workingDirectory: _testAppWebDirectory,
   );
 
-  print('BEGIN runWebServiceWorkerTestWithBlockedServiceWorkers(headless: $headless)\n');
+  print('BEGIN runWebServiceWorkerTestWithBlockedServiceWorkers(headless: $headless)');
   try {
     await _rebuildApp(version: 1, testType: ServiceWorkerTestType.blockedServiceWorkers, target: _targetWithBlockedServiceWorkers);
 
@@ -662,5 +662,5 @@ Future<void> runWebServiceWorkerTestWithBlockedServiceWorkers({
     );
     await server?.stop();
   }
-  print('END runWebServiceWorkerTestWithBlockedServiceWorkers(headless: $headless)\n');
+  print('END runWebServiceWorkerTestWithBlockedServiceWorkers(headless: $headless)');
 }

dev/bots/test/test_test.dart

@@ -17,7 +17,17 @@ import 'common.dart';
 /// will include the process result's stdio in the failure message.
 void expectExitCode(ProcessResult result, int expectedExitCode) {
   if (result.exitCode != expectedExitCode) {
-    fail('Failure due to exit code ${result.exitCode}\nSTDOUT:\n${result.stdout}\nSTDERR:\n${result.stderr}');
+    fail(
+      'Process ${result.pid} exitted with the wrong exit code.\n'
+      '\n'
+      'EXPECTED: exit code $expectedExitCode\n'
+      'ACTUAL: exit code ${result.exitCode}\n'
+      '\n'
+      'STDOUT:\n'
+      '${result.stdout}\n'
+      'STDERR:\n'
+      '${result.stderr}'
+    );
   }
 }
 
@@ -96,10 +106,13 @@ void main() {
   group('test.dart script', () {
     const ProcessManager processManager = LocalProcessManager();
 
-    Future<ProcessResult> runScript(
-        [Map<String, String>? environment, List<String> otherArgs = const <String>[]]) async {
+    Future<ProcessResult> runScript([
+        Map<String, String>? environment,
+        List<String> otherArgs = const <String>[],
+    ]) async {
       final String dart = path.absolute(
-          path.join('..', '..', 'bin', 'cache', 'dart-sdk', 'bin', 'dart'));
+        path.join('..', '..', 'bin', 'cache', 'dart-sdk', 'bin', 'dart'),
+      );
       final ProcessResult scriptProcess = processManager.runSync(<String>[
         dart,
         'test.dart',
@@ -112,21 +125,21 @@ void main() {
       // When updating this test, try to pick shard numbers that ensure we're checking
       // that unequal test distributions don't miss tests.
       ProcessResult result = await runScript(
-        <String, String>{'SHARD': 'test_harness_tests', 'SUBSHARD': '1_3'},
+        <String, String>{'SHARD': kTestHarnessShardName, 'SUBSHARD': '1_3'},
       );
       expectExitCode(result, 0);
-      expect(result.stdout, contains('Selecting subshard 1 of 3 (range 1-3 of 8)'));
+      expect(result.stdout, contains('Selecting subshard 1 of 3 (tests 1-3 of 8)'));
 
       result = await runScript(
-        <String, String>{'SHARD': 'test_harness_tests', 'SUBSHARD': '3_3'},
+        <String, String>{'SHARD': kTestHarnessShardName, 'SUBSHARD': '3_3'},
       );
       expectExitCode(result, 0);
-      expect(result.stdout, contains('Selecting subshard 3 of 3 (range 7-8 of 8)'));
+      expect(result.stdout, contains('Selecting subshard 3 of 3 (tests 7-8 of 8)'));
     });
 
     test('exits with code 1 when SUBSHARD index greater than total', () async {
       final ProcessResult result = await runScript(
-        <String, String>{'SHARD': 'test_harness_tests', 'SUBSHARD': '100_99'},
+        <String, String>{'SHARD': kTestHarnessShardName, 'SUBSHARD': '100_99'},
       );
       expectExitCode(result, 1);
       expect(result.stdout, contains('Invalid subshard name'));

dev/bots/utils.dart

@@ -2,28 +2,82 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:core' as core_internals show print;
+import 'dart:async';
 import 'dart:core' hide print;
 import 'dart:io' as system show exit;
 import 'dart:io' hide exit;
+import 'dart:math' as math;
 
 import 'package:meta/meta.dart';
 
+const Duration _quietTimeout = Duration(minutes: 10); // how long the output should be hidden between calls to printProgress before just being verbose
+
 final bool hasColor = stdout.supportsAnsiEscapes;
 
-final String bold = hasColor ? '\x1B[1m' : ''; // used for shard titles
-final String red = hasColor ? '\x1B[31m' : ''; // used for errors
-final String green = hasColor ? '\x1B[32m' : ''; // used for section titles, commands
-final String yellow = hasColor ? '\x1B[33m' : ''; // used for skips
-final String cyan = hasColor ? '\x1B[36m' : ''; // used for paths
-final String reverse = hasColor ? '\x1B[7m' : ''; // used for clocks
+final String bold = hasColor ? '\x1B[1m' : ''; // shard titles
+final String red = hasColor ? '\x1B[31m' : ''; // errors
+final String green = hasColor ? '\x1B[32m' : ''; // section titles, commands
+final String yellow = hasColor ? '\x1B[33m' : ''; // indications that a test was skipped (usually renders orange or brown)
+final String cyan = hasColor ? '\x1B[36m' : ''; // paths
+final String reverse = hasColor ? '\x1B[7m' : ''; // clocks
+final String gray = hasColor ? '\x1B[30m' : ''; // subtle decorative items (usually renders as dark gray)
+final String white = hasColor ? '\x1B[37m' : ''; // last log line (usually renders as light gray)
 final String reset = hasColor ? '\x1B[0m' : '';
-final String redLine = '$red━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━$reset';
 
-typedef PrintCallback = void Function(Object line);
+const int kESC = 0x1B;
+const int kOpenSquareBracket = 0x5B;
+const int kCSIParameterRangeStart = 0x30;
+const int kCSIParameterRangeEnd = 0x3F;
+const int kCSIIntermediateRangeStart = 0x20;
+const int kCSIIntermediateRangeEnd = 0x2F;
+const int kCSIFinalRangeStart = 0x40;
+const int kCSIFinalRangeEnd = 0x7E;
+
+
+String get redLine {
+  if (hasColor) {
+    return '$red${'━' * stdout.terminalColumns}$reset';
+  }
+  return '━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━';
+}
+
+String get clock {
+  final DateTime now = DateTime.now();
+  return '$reverse▌'
+         '${now.hour.toString().padLeft(2, "0")}:'
+         '${now.minute.toString().padLeft(2, "0")}:'
+         '${now.second.toString().padLeft(2, "0")}'
+         '▐$reset';
+}
+
+String prettyPrintDuration(Duration duration) {
+  String result = '';
+  final int minutes = duration.inMinutes;
+  if (minutes > 0) {
+    result += '${minutes}min ';
+  }
+  final int seconds = duration.inSeconds - minutes * 60;
+  final int milliseconds = duration.inMilliseconds - (seconds * 1000 + minutes * 60 * 1000);
+  result += '$seconds.${milliseconds.toString().padLeft(3, "0")}s';
+  return result;
+}
+
+typedef PrintCallback = void Function(Object? line);
+typedef VoidCallback = void Function();
 
 // Allow print() to be overridden, for tests.
-PrintCallback print = core_internals.print;
+//
+// Files that import this library should not import `print` from dart:core
+// and should not use dart:io's `stdout` or `stderr`.
+//
+// By default this hides log lines between `printProgress` calls unless a
+// timeout expires or anything calls `foundError`.
+//
+// Also used to implement `--verbose` in test.dart.
+PrintCallback print = _printQuietly;
+
+// Called by foundError and used to implement `--abort-on-error` in test.dart.
+VoidCallback? onError;
 
 bool get hasError => _hasError;
 bool _hasError = false;
@@ -31,22 +85,44 @@ bool _hasError = false;
 Iterable<String> get errorMessages => _errorMessages;
 List<String> _errorMessages = <String>[];
 
+final List<String> _pendingLogs = <String>[];
+Timer? _hideTimer; // When this is null, the output is verbose.
+
 void foundError(List<String> messages) {
   assert(messages.isNotEmpty);
-  print(redLine);
-  messages.forEach(print);
-  print(redLine);
+  // Make the error message easy to notice in the logs by
+  // wrapping it in a red box.
+  final int width = math.max(15, (hasColor ? stdout.terminalColumns : 80) - 1);
+  print('$red╔═╡${bold}ERROR$reset$red╞═${"═" * (width - 9)}');
+  for (final String message in messages.expand((String line) => line.split('\n'))) {
+    print('$red║$reset $message');
+  }
+  print('$red╚${"═" * width}');
+  // Normally, "print" actually prints to the log. To make the errors visible,
+  // and to include useful context, print the entire log up to this point, and
+  // clear it. Subsequent messages will continue to not be logged until there is
+  // another error.
+  _pendingLogs.forEach(_printLoudly);
+  _pendingLogs.clear();
   _errorMessages.addAll(messages);
   _hasError = true;
+  if (onError != null) {
+    onError!();
+  }
 }
 
 @visibleForTesting
 void resetErrorStatus() {
   _hasError = false;
   _errorMessages.clear();
+  _pendingLogs.clear();
+  _hideTimer?.cancel();
+  _hideTimer = null;
 }
 
 Never reportErrorsAndExit() {
+  _hideTimer?.cancel();
+  _hideTimer = null;
   print(redLine);
   print('For your convenience, the error messages reported above are repeated here:');
   _errorMessages.forEach(print);
@@ -54,35 +130,93 @@ Never reportErrorsAndExit() {
   system.exit(1);
 }
 
-String get clock {
-  final DateTime now = DateTime.now();
-  return '$reverse▌'
-         '${now.hour.toString().padLeft(2, "0")}:'
-         '${now.minute.toString().padLeft(2, "0")}:'
-         '${now.second.toString().padLeft(2, "0")}'
-         '▐$reset';
+void printProgress(String message) {
+  _pendingLogs.clear();
+  _hideTimer?.cancel();
+  _hideTimer = null;
+  print('$clock $message $reset');
+  if (hasColor) {
+    // This sets up a timer to switch to verbose mode when the tests take too long,
+    // so that if a test hangs we can see the logs.
+    // (This is only supported with a color terminal. When the terminal doesn't
+    // support colors, the scripts just print everything verbosely, that way in
+    // CI there's nothing hidden.)
+    _hideTimer = Timer(_quietTimeout, () {
+      _hideTimer = null;
+      _pendingLogs.forEach(_printLoudly);
+      _pendingLogs.clear();
+    });
+  }
 }
 
-String prettyPrintDuration(Duration duration) {
-  String result = '';
-  final int minutes = duration.inMinutes;
-  if (minutes > 0) {
-    result += '${minutes}min ';
+final Pattern _lineBreak = RegExp(r'[\r\n]');
+
+void _printQuietly(Object? message) {
+  // The point of this function is to avoid printing its output unless the timer
+  // has gone off in which case the function assumes verbose mode is active and
+  // prints everything. To show that progress is still happening though, rather
+  // than showing nothing at all, it instead shows the last line of output and
+  // keeps overwriting it. To do this in color mode, carefully measures the line
+  // of text ignoring color codes, which is what the parser below does.
+  if (_hideTimer != null) {
+    _pendingLogs.add(message.toString());
+    String line = '$message'.trimRight();
+    final int start = line.lastIndexOf(_lineBreak) + 1;
+    int index = start;
+    int length = 0;
+    while (index < line.length && length < stdout.terminalColumns) {
+      if (line.codeUnitAt(index) == kESC) { // 0x1B
+        index += 1;
+        if (index < line.length && line.codeUnitAt(index) == kOpenSquareBracket) { // 0x5B, [
+          // That was the start of a CSI sequence.
+          index += 1;
+          while (index < line.length && line.codeUnitAt(index) >= kCSIParameterRangeStart
+                                     && line.codeUnitAt(index) <= kCSIParameterRangeEnd) { // 0x30..0x3F
+            index += 1; // ...parameter bytes...
+          }
+          while (index < line.length && line.codeUnitAt(index) >= kCSIIntermediateRangeStart
+                                     && line.codeUnitAt(index) <= kCSIIntermediateRangeEnd) { // 0x20..0x2F
+            index += 1; // ...intermediate bytes...
+          }
+          if (index < line.length && line.codeUnitAt(index) >= kCSIFinalRangeStart
+                                  && line.codeUnitAt(index) <= kCSIFinalRangeEnd) { // 0x40..0x7E
+            index += 1; // ...final byte.
+          }
+        }
+      } else {
+        index += 1;
+        length += 1;
+      }
+    }
+    line = line.substring(start, index);
+    if (line.isNotEmpty) {
+      stdout.write('\r\x1B[2K$white$line$reset');
+    }
+  } else {
+    _printLoudly('$message');
   }
-  final int seconds = duration.inSeconds - minutes * 60;
-  final int milliseconds = duration.inMilliseconds - (seconds * 1000 + minutes * 60 * 1000);
-  result += '$seconds.${milliseconds.toString().padLeft(3, "0")}s';
-  return result;
 }
 
-void printProgress(String action, String workingDir, String command) {
-  print('$clock $action: cd $cyan$workingDir$reset; $green$command$reset');
+void _printLoudly(String message) {
+  if (hasColor) {
+    // Overwrite the last line written by _printQuietly.
+    stdout.writeln('\r\x1B[2K$reset${message.trimRight()}');
+  } else {
+    stdout.writeln(message);
+  }
 }
 
+// THE FOLLOWING CODE IS A VIOLATION OF OUR STYLE GUIDE
+// BECAUSE IT INTRODUCES A VERY FLAKY RACE CONDITION
+// https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#never-check-if-a-port-is-available-before-using-it-never-add-timeouts-and-other-race-conditions
+// DO NOT USE THE FOLLOWING FUNCTIONS
+// DO NOT WRITE CODE LIKE THE FOLLOWING FUNCTIONS
+// https://github.com/flutter/flutter/issues/109474
+
 int _portCounter = 8080;
 
 /// Finds the next available local port.
-Future<int> findAvailablePort() async {
+Future<int> findAvailablePortAndPossiblyCauseFlakyTests() async {
   while (!await _isPortAvailable(_portCounter)) {
     _portCounter += 1;
   }