Add a script to automatically update formatting test expectations. (#1230)

* Add a script to automatically update formatting test expectations.

It's not fully featured. It doesn't handle tests with selection
markers or Unicode escapes. But it handles everything else.

This should make it easier for me to update the tests as I work on the
Flutter style experimental branch.

Co-authored-by: Nate Bosch <[email protected]>

Author: munificent

lib/src/dart_formatter.dart

@@ -158,8 +158,7 @@ class DartFormatter {
             offset: token.offset - inputOffset,
             length: math.max(token.length, 1),
             errorCode: ParserErrorCode.UNEXPECTED_TOKEN,
-            arguments: [token.lexeme],
-        );
+            arguments: [token.lexeme]);
         throw FormatterException([error]);
       }
     }

lib/src/testing/test_file.dart

@@ -0,0 +1,187 @@
+import 'dart:io';
+import 'dart:isolate';
+
+import 'package:path/path.dart' as p;
+
+import '../../dart_style.dart';
+
+final _indentPattern = RegExp(r'\(indent (\d+)\)');
+final _fixPattern = RegExp(r'\(fix ([a-x-]+)\)');
+final _unicodeUnescapePattern = RegExp(r'×([0-9a-fA-F]{2,4})');
+final _unicodeEscapePattern = RegExp('[\x0a\x0c\x0d]');
+
+/// Get the absolute local file path to the package's "test" directory.
+Future<String> findTestDirectory() async {
+  var libraryUri = await Isolate.resolvePackageUri(
+      Uri.parse('package:dart_style/src/testing/test_file.dart'));
+  return p.normalize(
+      p.join(p.dirname(libraryUri!.toFilePath()), '../../../test'));
+}
+
+/// A file containing a series of formatting tests.
+class TestFile {
+  /// Finds all test files in the given directory relative to the package's
+  /// `test/` directory.
+  static Future<List<TestFile>> listDirectory(String name) async {
+    var testDir = await findTestDirectory();
+    var entries = Directory(p.join(testDir, name))
+        .listSync(recursive: true, followLinks: false);
+    entries.sort((a, b) => a.path.compareTo(b.path));
+
+    return [
+      for (var entry in entries)
+        if (entry is File &&
+            (entry.path.endsWith('.stmt') || entry.path.endsWith('.unit')))
+          TestFile._load(entry, p.relative(entry.path, from: testDir))
+    ];
+  }
+
+  /// Reads the test file from [path], which is relative to the package's
+  /// `test/` directory.
+  static Future<TestFile> read(String path) async {
+    var testDir = await findTestDirectory();
+    var file = File(p.join(testDir, path));
+    return TestFile._load(file, p.relative(file.path, from: testDir));
+  }
+
+  /// Reads the test file from [file].
+  factory TestFile._load(File file, String relativePath) {
+    var lines = file.readAsLinesSync();
+
+    // The first line may have a "|" to indicate the page width.
+    var i = 0;
+    int? pageWidth;
+    if (lines[i].endsWith('|')) {
+      pageWidth = lines[i].indexOf('|');
+      i++;
+    }
+
+    var tests = <FormatTest>[];
+
+    while (i < lines.length) {
+      var line = i + 1;
+      var description = lines[i++].replaceAll('>>>', '');
+      var fixes = <StyleFix>[];
+
+      // Let the test specify a leading indentation. This is handy for
+      // regression tests which often come from a chunk of nested code.
+      var leadingIndent = 0;
+      description = description.replaceAllMapped(_indentPattern, (match) {
+        leadingIndent = int.parse(match[1]!);
+        return '';
+      });
+
+      // Let the test specify fixes to apply.
+      description = description.replaceAllMapped(_fixPattern, (match) {
+        fixes.add(StyleFix.all.firstWhere((fix) => fix.name == match[1]));
+        return '';
+      });
+
+      var inputBuffer = StringBuffer();
+      while (!lines[i].startsWith('<<<')) {
+        inputBuffer.writeln(lines[i++]);
+      }
+
+      var outputDescription = lines[i].replaceAll('<<<', '');
+
+      var outputBuffer = StringBuffer();
+      while (++i < lines.length && !lines[i].startsWith('>>>')) {
+        outputBuffer.writeln(lines[i]);
+      }
+
+      var isCompilationUnit = file.path.endsWith('.unit');
+      var input = _extractSelection(_unescapeUnicode(inputBuffer.toString()),
+          isCompilationUnit: isCompilationUnit);
+      var output = _extractSelection(_unescapeUnicode(outputBuffer.toString()),
+          isCompilationUnit: isCompilationUnit);
+
+      tests.add(FormatTest(input, output, description.trim(),
+          outputDescription.trim(), line, fixes, leadingIndent));
+    }
+
+    return TestFile._(relativePath, pageWidth, tests);
+  }
+
+  TestFile._(this.path, this.pageWidth, this.tests);
+
+  /// The path to the test file, relative to the `test/` directory.
+  final String path;
+
+  /// The page width for tests in this file or `null` if the default should be
+  /// used.
+  final int? pageWidth;
+
+  /// The tests in this file.
+  final List<FormatTest> tests;
+
+  bool get isCompilationUnit => path.endsWith('.unit');
+}
+
+/// A single formatting test inside a [TestFile].
+class FormatTest {
+  /// The unformatted input.
+  final SourceCode input;
+
+  /// The expected output.
+  final SourceCode output;
+
+  /// The optional description of the test.
+  final String description;
+
+  /// If there is a remark on the "<<<" line, this is it.
+  final String outputDescription;
+
+  /// The 1-based index of the line where this test begins.
+  final int line;
+
+  /// The style fixes this test is applying.
+  final List<StyleFix> fixes;
+
+  /// The number of spaces of leading indentation that should be added to each
+  /// line.
+  final int leadingIndent;
+
+  FormatTest(this.input, this.output, this.description, this.outputDescription,
+      this.line, this.fixes, this.leadingIndent);
+
+  /// The line and description of the test.
+  String get label {
+    if (description.isEmpty) return 'line $line';
+    return 'line $line: $description';
+  }
+}
+
+/// Given a source string that contains ‹ and › to indicate a selection, returns
+/// a [SourceCode] with the text (with the selection markers removed) and the
+/// correct selection range.
+SourceCode _extractSelection(String source, {bool isCompilationUnit = false}) {
+  var start = source.indexOf('‹');
+  source = source.replaceAll('‹', '');
+
+  var end = source.indexOf('›');
+  source = source.replaceAll('›', '');
+
+  return SourceCode(source,
+      isCompilationUnit: isCompilationUnit,
+      selectionStart: start == -1 ? null : start,
+      selectionLength: end == -1 ? null : end - start);
+}
+
+/// Turn the special Unicode escape marker syntax used in the tests into real
+/// Unicode characters.
+///
+/// This does not use Dart's own string escape sequences so that we don't
+/// accidentally modify the Dart code being formatted.
+String _unescapeUnicode(String input) {
+  return input.replaceAllMapped(_unicodeUnescapePattern, (match) {
+    var codePoint = int.parse(match[1]!, radix: 16);
+    return String.fromCharCode(codePoint);
+  });
+}
+
+/// Turn the few Unicode characters used in tests back to their escape syntax.
+String escapeUnicode(String input) {
+  return input.replaceAllMapped(_unicodeEscapePattern, (match) {
+    return '×${match[0]!.codeUnitAt(0).toRadixString(16)}';
+  });
+}

test/comments/switch.stmt

@@ -238,4 +238,4 @@ e = switch (n) {
 >>> inline block comment
 e = switch (n) {  /* comment */  };
 <<<
-e = switch (n) {/* comment */};
+e = switch (n) {/* comment */};

test/fix_test.dart

@@ -10,13 +10,13 @@ import 'package:test/test.dart';
 
 import 'utils.dart';
 
-void main() {
-  testFile(
+void main() async {
+  await testFile(
       'fixes/named_default_separator.unit', [StyleFix.namedDefaultSeparator]);
-  testFile('fixes/doc_comments.stmt', [StyleFix.docComments]);
-  testFile('fixes/function_typedefs.unit', [StyleFix.functionTypedefs]);
-  testFile('fixes/optional_const.unit', [StyleFix.optionalConst]);
-  testFile('fixes/optional_new.stmt', [StyleFix.optionalNew]);
-  testFile('fixes/single_cascade_statements.stmt',
+  await testFile('fixes/doc_comments.stmt', [StyleFix.docComments]);
+  await testFile('fixes/function_typedefs.unit', [StyleFix.functionTypedefs]);
+  await testFile('fixes/optional_const.unit', [StyleFix.optionalConst]);
+  await testFile('fixes/optional_new.stmt', [StyleFix.optionalNew]);
+  await testFile('fixes/single_cascade_statements.stmt',
       [StyleFix.singleCascadeStatements]);
 }

test/formatter_test.dart

@@ -10,12 +10,12 @@ import 'package:test/test.dart';
 
 import 'utils.dart';
 
-void main() {
-  testDirectory('comments');
-  testDirectory('regression');
-  testDirectory('selections');
-  testDirectory('splitting');
-  testDirectory('whitespace');
+void main() async {
+  await testDirectory('comments');
+  await testDirectory('regression');
+  await testDirectory('selections');
+  await testDirectory('splitting');
+  await testDirectory('whitespace');
 
   test('throws a FormatterException on failed parse', () {
     var formatter = DartFormatter();

test/regression/0000/0025.stmt

@@ -21,4 +21,4 @@ return _parseHtml(content, id.path, logger,
       from: builder.join('/', builder.dirname(sourceId.path)));
 <<<
   return builder.relative(builder.join('/', id.path),
-      from: builder.join('/', builder.dirname(sourceId.path)));
+      from: builder.join('/', builder.dirname(sourceId.path)));

test/regression/0100/0141.unit

@@ -12,4 +12,4 @@
       Map<ast.SwitchCase, int> caseIndex,
       bool hasDefault) {
     ;
-  }
+  }

test/regression/0100/0158.unit

@@ -40,4 +40,4 @@ class ResultSet {
       json['platform'],
       json['release'],
       json['results'].map((result) => new Result.fromJson(result)).toList());
-}
+}

test/regression/1100/1198.stmt

@@ -28,4 +28,4 @@ e = switch ([1,]) {};
 <<<
 e = switch ([
   1,
-]) {};
+]) {};

test/regression/1200/1205.stmt

@@ -9,4 +9,4 @@ error(
 error(offset: 10, (
   code: 'unclosed-block',
   message: 'Block was left open',
-));
+));