Fix the sample analyzer to analyze dart:ui and make the analyzer null safe (#80742)

dev/bots/test/analyze-sample-code-test-dart-ui/ui.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.
+
+// @dart = 2.12
+
+// This is a dummy dart:ui package for the sample code analyzer tests to use.
+
+library dart.ui;
+
+/// Annotation used by Flutter's Dart compiler to indicate that an
+/// [Object.toString] override should not be replaced with a supercall.
+///
+/// {@tool sample}
+/// A sample if using keepToString to prevent replacement by a supercall.
+///
+/// ```dart
+/// class MyStringBuffer {
+///   StringBuffer _buffer = StringBuffer();
+///
+///   @keepToString
+///   @override
+///   String toString() {
+///     return _buffer.toString();
+///   }
+/// }
+/// ```
+/// {@end-tool}
+const _KeepToString keepToString = _KeepToString();
+
+class _KeepToString {
+  const _KeepToString();
+}
\ No newline at end of file

dev/bots/test/analyze_sample_code_test.dart

@@ -7,35 +7,42 @@ import 'dart:io';
 import 'common.dart';
 
 void main() {
-  test('analyze_sample_code', () {
+  // These tests don't run on Windows because the sample analyzer doesn't
+  // support Windows as a platform, since it is only run on Linux in the
+  // continuous integration tests.
+  if (Platform.isWindows) {
+    return;
+  }
+
+  test('analyze_sample_code smoke test', () {
     final ProcessResult process = Process.runSync(
       '../../bin/cache/dart-sdk/bin/dart',
-      <String>['analyze_sample_code.dart', 'test/analyze-sample-code-test-input'],
+      <String>['analyze_sample_code.dart', '--no-include-dart-ui', 'test/analyze-sample-code-test-input'],
     );
     final List<String> stdoutLines = process.stdout.toString().split('\n');
     final List<String> stderrLines = process.stderr.toString().split('\n')
       ..removeWhere((String line) => line.startsWith('Analyzer output:') || line.startsWith('Building flutter tool...'));
     expect(process.exitCode, isNot(equals(0)));
     expect(stderrLines, <String>[
-      'In sample starting at known_broken_documentation.dart:117:bool? _visible = true;',
+      'In sample starting at dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:117:bool? _visible = true;',
       '>>> info: Use late for private members with non-nullable type (use_late_for_private_fields_and_variables)',
-      'In sample starting at known_broken_documentation.dart:117:      child: Text(title),',
+      'In sample starting at dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:117:      child: Text(title),',
       '>>> error: The final variable \'title\' can\'t be read because it is potentially unassigned at this point (read_potentially_unassigned_final)',
-      'known_broken_documentation.dart:30:9: new Opacity(',
+      'dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:30:9: new Opacity(',
       '>>> info: Unnecessary new keyword (unnecessary_new)',
-      'known_broken_documentation.dart:62:9: new Opacity(',
+      'dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:62:9: new Opacity(',
       '>>> info: Unnecessary new keyword (unnecessary_new)',
-      'known_broken_documentation.dart:95:9: const text0 = Text(\'Poor wandering ones!\');',
+      'dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:95:9: const text0 = Text(\'Poor wandering ones!\');',
       '>>> info: Specify type annotations (always_specify_types)',
-      'known_broken_documentation.dart:103:9: const text1 = _Text(\'Poor wandering ones!\');',
+      'dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:103:9: const text1 = _Text(\'Poor wandering ones!\');',
       '>>> info: Specify type annotations (always_specify_types)',
-      'known_broken_documentation.dart:111:9: final String? bar = \'Hello\';',
+      'dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:111:9: final String? bar = \'Hello\';',
       '>>> info: Prefer const over final for declarations (prefer_const_declarations)',
-      'known_broken_documentation.dart:111:23: final String? bar = \'Hello\';',
+      'dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:111:23: final String? bar = \'Hello\';',
       '>>> info: Use a non-nullable type for a final variable initialized with a non-nullable value (unnecessary_nullable_for_final_variable_declarations)',
-      'known_broken_documentation.dart:112:9: final int foo = null;',
+      'dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:112:9: final int foo = null;',
       '>>> info: Prefer const over final for declarations (prefer_const_declarations)',
-      'known_broken_documentation.dart:112:25: final int foo = null;',
+      'dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:112:25: final int foo = null;',
       '>>> error: A value of type \'Null\' can\'t be assigned to a variable of type \'int\' (invalid_assignment)',
       '',
       'Found 2 sample code errors.',
@@ -46,5 +53,23 @@ void main() {
       'Starting analysis of code samples.',
       '',
     ]);
-  }, skip: Platform.isWindows);
+  });
+  test('Analyzes dart:ui code', () {
+    final ProcessResult process = Process.runSync(
+      '../../bin/cache/dart-sdk/bin/dart',
+      <String>[
+        'analyze_sample_code.dart',
+        '--dart-ui-location',
+        'test/analyze-sample-code-test-dart-ui',
+        'test/analyze-sample-code-test-input',
+      ],
+    );
+    final List<String> stdoutLines = process.stdout.toString().split('\n');
+    expect(process.exitCode, isNot(equals(0)));
+    expect(stdoutLines, equals(<String>[
+      // There is one sample code section in the test's dummy dart:ui code.
+      'Found 8 snippet code blocks, 1 sample code sections, and 2 dartpad sections.',
+      '',
+    ]));
+  });
 }

dev/snippets/lib/snippets.dart

@@ -179,7 +179,9 @@ class SnippetGenerator {
         description.add(line);
       } else {
         assert(language != null);
-        components.last.contents.add(line);
+        if (components.isNotEmpty) {
+          components.last.contents.add(line);
+        }
       }
     }
     return <_ComponentTuple>[