Teach dart_package to understand the packages/ subdirectory

third_party/dart-packages/matcher/matcher/src/util.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 matcher.util;
-
-import 'core_matchers.dart';
-import 'interfaces.dart';
-
-/// A [Map] between whitespace characters and their escape sequences.
-const _escapeMap = const {
-  '\n': r'\n',
-  '\r': r'\r',
-  '\f': r'\f',
-  '\b': r'\b',
-  '\t': r'\t',
-  '\v': r'\v',
-};
-
-/// A [RegExp] that matches whitespace characters that should be escaped.
-final _escapeRegExp =
-    new RegExp("[${_escapeMap.keys.map(_getHexLiteral).join()}]");
-
-/// Useful utility for nesting match states.
-void addStateInfo(Map matchState, Map values) {
-  var innerState = new Map.from(matchState);
-  matchState.clear();
-  matchState['state'] = innerState;
-  matchState.addAll(values);
-}
-
-/// Takes an argument and returns an equivalent [Matcher].
-///
-/// If the argument is already a matcher this does nothing,
-/// else if the argument is a function, it generates a predicate
-/// function matcher, else it generates an equals matcher.
-Matcher wrapMatcher(x) {
-  if (x is Matcher) {
-    return x;
-  } else if (x is Function) {
-    return predicate(x);
-  } else {
-    return equals(x);
-  }
-}
-
-/// Returns [str] with all whitespace characters represented as their escape
-/// sequences.
-///
-/// Backslash characters are escaped as `\\`
-String escape(String str) {
-  str = str.replaceAll('\\', r'\\');
-  return str.replaceAllMapped(_escapeRegExp, (match) {
-    return _escapeMap[match[0]];
-  });
-}
-
-/// Given single-character string, return the hex-escaped equivalent.
-String _getHexLiteral(String input) {
-  int rune = input.runes.single;
-  return r'\x' + rune.toRadixString(16).padLeft(2, '0');
-}