Add a string_scanner package.

pkg/string_scanner/test/error_format_test.dart

+// Copyright (c) 2014, 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.
+
+library string_scanner.error_format_test;
+
+import 'package:string_scanner/string_scanner.dart';
+import 'package:unittest/unittest.dart';
+
+void main() {
+  test('points to the first unconsumed character', () {
+    var scanner = new StringScanner('foo bar baz');
+    scanner.expect('foo ');
+    expect(() => scanner.expect('foo'), throwsFormattedError('''
+Expected "foo" on line 1, column 5.
+foo bar baz
+    ^'''));
+  });
+
+  test('prints the correct line', () {
+    var scanner = new StringScanner('foo bar baz\ndo re mi\nearth fire water');
+    scanner.expect('foo bar baz\ndo ');
+    expect(() => scanner.expect('foo'), throwsFormattedError('''
+Expected "foo" on line 2, column 4.
+do re mi
+   ^'''));
+  });
+
+  test('handles the beginning of the string correctly', () {
+    var scanner = new StringScanner('foo bar baz');
+    expect(() => scanner.expect('zap'), throwsFormattedError('''
+Expected "zap" on line 1, column 1.
+foo bar baz
+^'''));
+  });
+
+  test('handles the end of the string correctly', () {
+    var scanner = new StringScanner('foo bar baz');
+    scanner.expect('foo bar baz');
+    expect(() => scanner.expect('bang'), throwsFormattedError('''
+Expected "bang" on line 1, column 12.
+foo bar baz
+           ^'''));
+  });
+
+  test('handles an empty string correctly', () {
+    expect(() => new StringScanner('').expect('foo'), throwsFormattedError('''
+Expected "foo" on line 1, column 1.
+
+^'''));
+  });
+
+  group("expected name", () {
+    test("uses the provided name", () {
+      expect(() => new StringScanner('').expect('foo bar', name: 'zap'),
+          throwsFormattedError('''
+Expected zap on line 1, column 1.
+
+^'''));
+    });
+
+    test("escapes string quotes", () {
+      expect(() => new StringScanner('').expect('foo"bar'),
+          throwsFormattedError('''
+Expected "foo\\"bar" on line 1, column 1.
+
+^'''));
+    });
+
+    test("escapes string backslashes", () {
+      expect(() => new StringScanner('').expect('foo\\bar'),
+          throwsFormattedError('''
+Expected "foo\\\\bar" on line 1, column 1.
+
+^'''));
+    });
+
+    test("prints PERL-style regexps", () {
+      expect(() => new StringScanner('').expect(new RegExp(r'foo')),
+          throwsFormattedError('''
+Expected /foo/ on line 1, column 1.
+
+^'''));
+    });
+
+    test("escape regexp forward slashes", () {
+      expect(() => new StringScanner('').expect(new RegExp(r'foo/bar')),
+          throwsFormattedError('''
+Expected /foo\\/bar/ on line 1, column 1.
+
+^'''));
+    });
+
+    test("does not escape regexp backslashes", () {
+      expect(() => new StringScanner('').expect(new RegExp(r'foo\bar')),
+          throwsFormattedError('''
+Expected /foo\\bar/ on line 1, column 1.
+
+^'''));
+    });
+  });
+}
+
+Matcher throwsFormattedError(String format) {
+  return throwsA(predicate((error) {
+    expect(error, isFormatException);
+    expect(error.message, equals(format));
+    return true;
+  }));
+}