Add failure only reporter (#2190)

Closes #829

Copies the expanded reporter and test and removes output unrelated to
failed tests.

pkgs/test/pubspec.yaml

@@ -35,7 +35,7 @@ dependencies:
 
   # Use an exact version until the test_api and test_core package are stable.
   test_api: 0.7.0
-  test_core: 0.6.0
+  test_core: 0.6.1
 
   typed_data: ^1.3.0
   web_socket_channel: ^2.0.0

pkgs/test/test/runner/failures_only_reporter_test.dart

@@ -0,0 +1,257 @@
+// Copyright (c) 2024, 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.
+
+@TestOn('vm')
+library;
+
+import 'dart:async';
+
+import 'package:test/test.dart';
+import 'package:test_descriptor/test_descriptor.dart' as d;
+
+import '../io.dart';
+
+void main() {
+  setUpAll(precompileTestExecutable);
+
+  test('reports when no tests are run', () async {
+    await d.file('test.dart', 'void main() {}').create();
+
+    var test = await runTest(['test.dart'], reporter: 'failures-only');
+    expect(test.stdout, emitsThrough(contains('No tests ran.')));
+    await test.shouldExit(79);
+  });
+
+  test('runs several successful tests and reports only at the end', () {
+    return _expectReport('''
+        test('success 1', () {});
+        test('success 2', () {});
+        test('success 3', () {});''', '''
+        +3: All tests passed!''');
+  });
+
+  test('runs several failing tests and reports when each fails', () {
+    return _expectReport('''
+        test('failure 1', () => throw TestFailure('oh no'));
+        test('failure 2', () => throw TestFailure('oh no'));
+        test('failure 3', () => throw TestFailure('oh no'));''', '''
+        +0 -1: failure 1 [E]
+          oh no
+          test.dart 6:33  main.<fn>
+
+        +0 -2: failure 2 [E]
+          oh no
+          test.dart 7:33  main.<fn>
+
+        +0 -3: failure 3 [E]
+          oh no
+          test.dart 8:33  main.<fn>
+
+        +0 -3: Some tests failed.''');
+  });
+
+  test('includes the full stack trace with --verbose-trace', () async {
+    await d.file('test.dart', '''
+import 'dart:async';
+
+import 'package:test/test.dart';
+
+void main() {
+  test("failure", () => throw "oh no");
+}
+''').create();
+
+    var test = await runTest(['--verbose-trace', 'test.dart'],
+        reporter: 'failures-only');
+    expect(test.stdout, emitsThrough(contains('dart:async')));
+    await test.shouldExit(1);
+  });
+
+  test('reports only failing tests amid successful tests', () {
+    return _expectReport('''
+        test('failure 1', () => throw TestFailure('oh no'));
+        test('success 1', () {});
+        test('failure 2', () => throw TestFailure('oh no'));
+        test('success 2', () {});''', '''
+        +0 -1: failure 1 [E]
+          oh no
+          test.dart 6:33  main.<fn>
+
+        +1 -2: failure 2 [E]
+          oh no
+          test.dart 8:33  main.<fn>
+
+        +2 -2: Some tests failed.''');
+  });
+
+  group('print:', () {
+    test('handles multiple prints', () {
+      return _expectReport('''
+        test('test', () {
+          print("one");
+          print("two");
+          print("three");
+          print("four");
+        });''', '''
+        +0: test
+        one
+        two
+        three
+        four
+        +1: All tests passed!''');
+    });
+
+    test('handles a print after the test completes', () {
+      return _expectReport('''
+        // This completer ensures that the test isolate isn't killed until all
+        // prints have happened.
+        var testDone = Completer();
+        var waitStarted = Completer();
+        test('test', () async {
+          waitStarted.future.then((_) {
+            Future(() => print("one"));
+            Future(() => print("two"));
+            Future(() => print("three"));
+            Future(() => print("four"));
+            Future(testDone.complete);
+          });
+        });
+
+        test('wait', () {
+          waitStarted.complete();
+          return testDone.future;
+        });''', '''
+        +1: test
+        one
+        two
+        three
+        four
+        +2: All tests passed!''');
+    });
+
+    test('interleaves prints and errors', () {
+      return _expectReport('''
+        // This completer ensures that the test isolate isn't killed until all
+        // prints have happened.
+        var completer = Completer();
+        test('test', () {
+          scheduleMicrotask(() {
+            print("three");
+            print("four");
+            throw "second error";
+          });
+
+          scheduleMicrotask(() {
+            print("five");
+            print("six");
+            completer.complete();
+          });
+
+          print("one");
+          print("two");
+          throw "first error";
+        });
+
+        test('wait', () => completer.future);''', '''
+        +0: test
+        one
+        two
+        +0 -1: test [E]
+          first error
+          test.dart 24:11  main.<fn>
+
+        three
+        four
+          second error
+          test.dart 13:13  main.<fn>.<fn>
+          ===== asynchronous gap ===========================
+          dart:async       scheduleMicrotask
+          test.dart 10:11  main.<fn>
+
+        five
+        six
+        +1 -1: Some tests failed.''');
+    });
+  });
+
+  group('skip:', () {
+    test('does not emit for skips', () {
+      return _expectReport('''
+          test('skip 1', () {}, skip: true);
+          test('skip 2', () {}, skip: true);
+          test('skip 3', () {}, skip: true);''', '''
+          +0 ~3: All tests skipped.''');
+    });
+
+    test('runs skipped tests along with successful and failing tests', () {
+      return _expectReport('''
+          test('failure 1', () => throw TestFailure('oh no'));
+          test('skip 1', () {}, skip: true);
+          test('success 1', () {});
+          test('failure 2', () => throw TestFailure('oh no'));
+          test('skip 2', () {}, skip: true);
+          test('success 2', () {});''', '''
+          +0 -1: failure 1 [E]
+            oh no
+            test.dart 6:35  main.<fn>
+
+          +1 ~1 -2: failure 2 [E]
+            oh no
+            test.dart 9:35  main.<fn>
+
+          +2 ~2 -2: Some tests failed.''');
+    });
+  });
+
+  test('Directs users to enable stack trace chaining if disabled', () async {
+    await _expectReport(
+        '''test('failure 1', () => throw TestFailure('oh no'));''', '''
+        +0 -1: failure 1 [E]
+          oh no
+          test.dart 6:25  main.<fn>
+
+        +0 -1: Some tests failed.
+
+        Consider enabling the flag chain-stack-traces to receive more detailed exceptions.
+        For example, 'dart test --chain-stack-traces'.''',
+        chainStackTraces: false);
+  });
+}
+
+Future<void> _expectReport(String tests, String expected,
+    {List<String> args = const [], bool chainStackTraces = true}) async {
+  await d.file('test.dart', '''
+    import 'dart:async';
+
+    import 'package:test/test.dart';
+
+    void main() {
+$tests
+    }
+  ''').create();
+
+  var test = await runTest([
+    'test.dart',
+    if (chainStackTraces) '--chain-stack-traces',
+    ...args,
+  ], reporter: 'failures-only');
+  await test.shouldExit();
+
+  var stdoutLines = await test.stdoutStream().toList();
+
+  // Remove excess trailing whitespace.
+  var actual = stdoutLines.map((line) {
+    if (line.startsWith('  ') || line.isEmpty) return line.trimRight();
+    return line.trim();
+  }).join('\n');
+
+  // Un-indent the expected string.
+  var indentation = expected.indexOf(RegExp('[^ ]'));
+  expected = expected.split('\n').map((line) {
+    if (line.isEmpty) return line;
+    return line.substring(indentation);
+  }).join('\n');
+
+  expect(actual, equals(expected));
+}

pkgs/test/test/runner/runner_test.dart

@@ -108,6 +108,7 @@ Output:
 
           [compact]                   A single line, updated continuously.
           [expanded] (default)        A separate line for each update.
+          [failures-only]             A separate line for failing tests with no output for passing tests
           [github]                    A custom reporter for GitHub Actions (the default reporter when running on GitHub Actions).
           [json]                      A machine-readable format (see https://dart.dev/go/test-docs/json_reporter.md).
           [silent]                    A reporter with no output. May be useful when only the exit code is meaningful.

pkgs/test_core/lib/src/runner/configuration/reporters.dart

@@ -11,6 +11,7 @@ import '../engine.dart';
 import '../reporter.dart';
 import '../reporter/compact.dart';
 import '../reporter/expanded.dart';
+import '../reporter/failures_only.dart';
 import '../reporter/github.dart';
 import '../reporter/json.dart';
 
@@ -46,6 +47,14 @@ final _allReporters = <String, ReporterDetails>{
               Directory(config.testSelections.keys.single).existsSync(),
           printPlatform: config.suiteDefaults.runtimes.length > 1 ||
               config.suiteDefaults.compilerSelections != null)),
+  'failures-only': ReporterDetails(
+      'A separate line for failing tests with no output for passing tests',
+      (config, engine, sink) => FailuresOnlyReporter.watch(engine, sink,
+          color: config.color,
+          printPath: config.testSelections.length > 1 ||
+              Directory(config.testSelections.keys.single).existsSync(),
+          printPlatform: config.suiteDefaults.runtimes.length > 1 ||
+              config.suiteDefaults.compilerSelections != null)),
   'github': ReporterDetails(
       'A custom reporter for GitHub Actions '
       '(the default reporter when running on GitHub Actions).',