pkg/(unit)test: include a copy of old matcher

lib/src/matcher/expect.dart

+// Copyright (c) 2012, 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.expect;
+
+import 'core_matchers.dart';
+import 'description.dart';
+import 'interfaces.dart';
+import 'util.dart';
+
+/// The objects thrown by the default failure handler.
+class TestFailure extends Error {
+  final String message;
+
+  TestFailure(this.message);
+
+  String toString() => message;
+}
+
+/// Failed matches are reported using a default IFailureHandler.
+/// The default implementation simply throws [TestFailure]s;
+/// this can be replaced by some other implementation of
+/// IFailureHandler by calling configureExpectHandler.
+abstract class FailureHandler {
+  /// This handles failures given a textual decription
+  void fail(String reason);
+
+  /// This handles failures given the actual [value], the [matcher]
+  /// the [reason] (argument from [expect]), some additonal [matchState]
+  /// generated by the [matcher], and a verbose flag which controls in
+  /// some cases how much [matchState] information is used. It will use
+  /// these to create a detailed error message (typically by calling
+  /// an [ErrorFormatter]) and then call [fail] with this message.
+  void failMatch(
+      actual, Matcher matcher, String reason, Map matchState, bool verbose);
+}
+
+/// The ErrorFormatter type is used for functions that
+/// can be used to build up error reports upon [expect] failures.
+/// There is one built-in implementation ([defaultErrorFormatter])
+/// which is used by the default failure handler. If the failure handler
+/// is replaced it may be desirable to replace the [stringDescription]
+/// error formatter with another.
+typedef String ErrorFormatter(
+    actual, Matcher matcher, String reason, Map matchState, bool verbose);
+
+/// This Function is used by certain Matchers to catch certain exceptions.
+///
+/// Some matchers, like those for Futures and exception testing,
+/// can fail in asynchronous sections, and throw exceptions.
+/// A user of this library will typically want to catch and handle
+/// such exceptions. The [wrapAsync] property is a function that
+/// can wrap callbacks used by these Matchers so that they can be
+/// used safely. For example, the unittest library will set this
+/// to be `expectAsync`. By default this is an identity function.
+Function wrapAsync = (Function f, [id]) => f;
+
+/// Assert that [actual] matches [matcher].
+///
+/// This is the main assertion function. [reason] is optional and is typically
+/// not supplied, as a reason is generated from the matcher; if [reason]
+/// is included it is appended to the reason generated by the matcher.
+///
+/// [matcher] can be a value in which case it will be wrapped in an
+/// [equals] matcher.
+///
+/// If the assertion fails, then the default behavior is to throw a
+/// [TestFailure], but this behavior can be changed by calling
+/// [configureExpectFailureHandler] and providing an alternative handler that
+/// implements the [IFailureHandler] interface. It is also possible to
+/// pass a [failureHandler] to [expect] as a final parameter for fine-
+/// grained control.
+///
+/// In some cases extra diagnostic info can be produced on failure (for
+/// example, stack traces on mismatched exceptions). To enable these,
+/// [verbose] should be specified as true;
+void expect(actual, matcher,
+    {String reason, FailureHandler failureHandler, bool verbose: false}) {
+  matcher = wrapMatcher(matcher);
+  bool doesMatch;
+  var matchState = {};
+  try {
+    doesMatch = matcher.matches(actual, matchState);
+  } catch (e, trace) {
+    doesMatch = false;
+    if (reason == null) {
+      reason = '${(e is String) ? e : e.toString()} at $trace';
+    }
+  }
+  if (!doesMatch) {
+    if (failureHandler == null) {
+      failureHandler = getOrCreateExpectFailureHandler();
+    }
+    failureHandler.failMatch(actual, matcher, reason, matchState, verbose);
+  }
+}
+
+void fail(String message, {FailureHandler failureHandler}) {
+  if (failureHandler == null) {
+    failureHandler = getOrCreateExpectFailureHandler();
+  }
+  failureHandler.fail(message);
+}
+
+// The handler for failed asserts.
+FailureHandler _assertFailureHandler = null;
+
+// The default failure handler that throws [TestFailure]s.
+class DefaultFailureHandler implements FailureHandler {
+  DefaultFailureHandler() {
+    if (_assertErrorFormatter == null) {
+      _assertErrorFormatter = _defaultErrorFormatter;
+    }
+  }
+  void fail(String reason) {
+    throw new TestFailure(reason);
+  }
+  void failMatch(
+      actual, Matcher matcher, String reason, Map matchState, bool verbose) {
+    fail(_assertErrorFormatter(actual, matcher, reason, matchState, verbose));
+  }
+}
+
+/// Changes the default failure handler for [expect].
+///
+/// [handler] is a reference to the new handler; if this is omitted
+/// or null then the failure handler is reset to the default, which
+/// throws [TestFailure]s on [expect] assertion failures.
+void configureExpectFailureHandler([FailureHandler handler = null]) {
+  if (handler == null) {
+    handler = new DefaultFailureHandler();
+  }
+  _assertFailureHandler = handler;
+}
+
+FailureHandler getOrCreateExpectFailureHandler() {
+  if (_assertFailureHandler == null) {
+    configureExpectFailureHandler();
+  }
+  return _assertFailureHandler;
+}
+
+// The error message formatter for failed asserts.
+ErrorFormatter _assertErrorFormatter = null;
+
+// The default error formatter implementation.
+String _defaultErrorFormatter(
+    actual, Matcher matcher, String reason, Map matchState, bool verbose) {
+  var description = new StringDescription();
+  description.add('Expected: ').addDescriptionOf(matcher).add('\n');
+  description.add('  Actual: ').addDescriptionOf(actual).add('\n');
+
+  var mismatchDescription = new StringDescription();
+  matcher.describeMismatch(actual, mismatchDescription, matchState, verbose);
+
+  if (mismatchDescription.length > 0) {
+    description.add('   Which: ${mismatchDescription}\n');
+  }
+  if (reason != null) {
+    description.add(reason).add('\n');
+  }
+  return description.toString();
+}
+
+/// Changes the failure message formatter for expect().
+///
+/// [formatter] is a reference to the new formatter; if this is omitted or
+/// null then the failure formatter is reset to the default. The new
+/// formatter is returned; this allows custom expect handlers to easily
+/// get a reference to the default formatter.
+ErrorFormatter configureExpectFormatter([ErrorFormatter formatter = null]) {
+  if (formatter == null) {
+    formatter = _defaultErrorFormatter;
+  }
+  return _assertErrorFormatter = formatter;
+}