Refactor and clean up the status file parsing code.

tools/testing/dart/expectation_set.dart

Index: tools/testing/dart/expectation_set.dart
diff --git a/tools/testing/dart/expectation_set.dart b/tools/testing/dart/expectation_set.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f7d135f98beceabc9b03ced89e93080ddea90282
--- /dev/null
+++ b/tools/testing/dart/expectation_set.dart
@@ -0,0 +1,118 @@
+// Copyright (c) 2017, 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.
+
+import 'expectation.dart';
+import 'status_file.dart';
+
+/// Tracks the [Expectation]s associated with a set of file paths.
+///
+/// For any given file path, returns the expected test results for that file.
+/// A set can be loaded from a collection of status files. A file path may
+/// exist in multiple files (or even multiple sections within the file). When
+/// that happens, all of the expectations of every entry are combined.
+class ExpectationSet {
+  /// Reads the expectations defined by the status files at [statusFilePaths]
+  /// given [environment].
+  static ExpectationSet read(
+      List<String> statusFilePaths, Map<String, dynamic> environment) {
+    var expectations = new ExpectationSet._();
+    for (var path in statusFilePaths) {
+      var file = new StatusFile.read(path);
+      for (var section in file.sections) {
+        if (section.isEnabled(environment)) {
+          for (var entry in section.entries) {
+            expectations.addEntry(entry);
+          }
+        }
+      }
+    }
+
+    return expectations;
+  }
+
+  // Only create one copy of each Set<Expectation>.
+  // We just use .toString as a key, so we may make a few
+  // sets that only differ in their toString element order.
+  static Map<String, Set<Expectation>> _cachedSets = {};
+
+  Map<String, Set<Expectation>> _map = {};
+  Map<String, List<RegExp>> _keyToRegExps;
+
+  /// Create a TestExpectations object. See the [expectations] method
+  /// for an explanation of matching.
+  ExpectationSet._();
+
+  /// Add [entry] to the set of expectations.
+  void addEntry(StatusEntry entry) {
+    // Once we have started using the expectations we cannot add more
+    // rules.
+    if (_keyToRegExps != null) {
+      throw new StateError("Cannot add entries after it is already in use.");
+    }
+
+    _map
+        .putIfAbsent(entry.path, () => new Set<Expectation>())
+        .addAll(entry.expectations);
+  }
+
+  /// Get the expectations for the test at [path].
+  ///
+  /// For every (key, expectation) pair, matches the key with the file name.
+  /// Returns the union of the expectations for all the keys that match.
+  ///
+  /// Normal matching splits the key and the filename into path components and
+  /// checks that the anchored regular expression "^$keyComponent\$" matches
+  /// the corresponding filename component.
+  Set<Expectation> expectations(String path) {
+    var result = new Set<Expectation>();
+    var parts = path.split('/');
+
+    // Create mapping from keys to list of RegExps once and for all.
+    _preprocessForMatching();
+
+    _map.forEach((key, expectations) {
+      var regExps = _keyToRegExps[key];
+      if (regExps.length > parts.length) return;
+
+      for (var i = 0; i < regExps.length; i++) {
+        if (!regExps[i].hasMatch(parts[i])) return;
+      }
+
+      // If all components of the status file key matches the filename
+      // add the expectations to the result.
+      result.addAll(expectations);
+    });
+
+    // If no expectations were found the expectation is that the test
+    // passes.
+    if (result.isEmpty) {
+      result.add(Expectation.pass);
+    }
+    return _cachedSets.putIfAbsent(result.toString(), () => result);
+  }
+
+  /// Preprocesses the expectations for matching against filenames. Generates
+  /// lists of regular expressions once and for all for each key.
+  void _preprocessForMatching() {
+    if (_keyToRegExps != null) return;
+
+    _keyToRegExps = {};
+    var regExpCache = <String, RegExp>{};
+
+    _map.forEach((key, expectations) {
+      if (_keyToRegExps[key] != null) return;
+      var splitKey = key.split('/');
+      var regExps = new List<RegExp>(splitKey.length);
+
+      for (var i = 0; i < splitKey.length; i++) {
+        var component = splitKey[i];
+        var regExp = regExpCache.putIfAbsent(component,
+            () => new RegExp("^${splitKey[i]}\$".replaceAll('*', '.*')));
+        regExps[i] = regExp;
+      }
+
+      _keyToRegExps[key] = regExps;
+    });
+  }
+}