Refactor and clean up the status file parsing code.

tools/testing/dart/status_file.dart

Index: tools/testing/dart/status_file.dart
diff --git a/tools/testing/dart/status_file.dart b/tools/testing/dart/status_file.dart
new file mode 100644
index 0000000000000000000000000000000000000000..cd2d65f2f9511fadf5a356abb930d42fae257000
--- /dev/null
+++ b/tools/testing/dart/status_file.dart
@@ -0,0 +1,164 @@
+// 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 'dart:io';
+
+import 'expectation.dart';
+import 'status_expression.dart';
+
+/// Splits out a trailing line comment
+final _commentPattern = new RegExp("^([^#]*)(#.*)?\$");
+
+/// Matches the header that begins a new section, like:
+///
+///     [ $compiler == dart2js && $minified ]
+final _sectionPattern = new RegExp(r"^\[([^\]]+)\]");
+
+/// Matches an entry that defines the status for a path in the current section,
+/// like:
+///
+///     some/path/to/some_test: Pass || Fail
+final _entryPattern = new RegExp(r"\s*([^: ]*)\s*:(.*)");
+
+/// Matches an issue number in a comment, like:
+///
+///     blah_test: Fail # Issue 1234
+///                       ^^^^
+final _issuePattern = new RegExp("[Ii]ssue ([0-9]+)");
+
+/// A parsed status file, which describes how a collection of tests are
+/// expected to behave under various configurations and conditions.
+///
+/// Each status file is made of a series of sections. Each section begins with
+/// a header, followed by a series of entries. A header is enclosed in square
+/// brackets and contains a Boolean expression. That expression is evaluated in
+/// an environment. If it evaluates to true, then the entries after the header
+/// take effect.
+///
+/// Each entry is a glob-like file path followed by a colon and then a
+/// comma-separated list of [Expectation]s. The path may point to an individual
+/// file, or a directory, in which case it applies to all files under that path.
+///
+/// Entries may also appear before any section header, in which case they
+/// always apply.
+class StatusFile {
+  final List<StatusSection> sections = [];
+
+  /// Parses the status file at [path].
+  StatusFile.read(String path) {
+    var lines = new File(path).readAsLinesSync();
+
+    // The current section whose rules are being parsed.
+    StatusSection section;
+
+    var lineNumber = 0;
+    for (var line in lines) {
+      lineNumber++;
+
+      // Strip off the comment and whitespace.
+      var match = _commentPattern.firstMatch(line);
+      var source = "";
+      var comment = "";
+      if (match != null) {
+        source = match[1].trim();
+        comment = match[2] ?? "";
+      }
+
+      // Ignore empty (or comment-only) lines.
+      if (source.isEmpty) continue;
+
+      // See if we are starting a new section.
+      match = _sectionPattern.firstMatch(source);
+      if (match != null) {
+        var condition = Expression.parse(match[1].trim());
+        section = new StatusSection(condition);
+        sections.add(section);
+        continue;
+      }
+
+      // Otherwise, it should be a new entry under the current section.
+      match = _entryPattern.firstMatch(source);
+      if (match != null) {
+        var path = match[1].trim();
+        // TODO(whesse): Handle test names ending in a wildcard (*).
+        var expectations = _parseExpectations(match[2]);
+        var issue = _issueNumber(comment);
+
+        // If we haven't found a section header yet, create an implicit section
+        // that matches everything.
+        if (section == null) {
+          section = new StatusSection(null);
+          sections.add(section);
+        }
+
+        section.entries.add(new StatusEntry(path, expectations, issue));
+        continue;
+      }
+
+      throw new FormatException(
+          "Could not parse line $lineNumber of status file '$path':\n$line");
+    }
+  }
+
+  /// Parses a comma-separated list of expectation names from [text].
+  List<Expectation> _parseExpectations(String text) {
+    return text
+        .split(",")
+        .map((name) => Expectation.find(name.trim()))
+        .toList();
+  }
+
+  /// Returns the issue number embedded in [comment] or `null` if there is none.
+  int _issueNumber(String comment) {
+    var match = _issuePattern.firstMatch(comment);
+    if (match == null) return null;
+
+    return int.parse(match[1], onError: (_) => null);
+  }
+
+  String toString() {
+    var buffer = new StringBuffer();
+    for (var section in sections) {
+      buffer.writeln("[${section._condition}]");
+
+      for (var entry in section.entries) {
+        buffer.write("${entry.path}: ${entry.expectations.join(', ')}");
+        if (entry.issue != null) buffer.write(" # Issue ${entry.issue}");
+        buffer.writeln();
+      }
+
+      buffer.writeln();
+    }
+
+    return buffer.toString();
+  }
+}
+
+/// One section in a status file.
+///
+/// Contains the condition from the header that begins the section, then all of
+/// the entries within the section.
+class StatusSection {
+  /// The expression that determines when this section is applied.
+  ///
+  /// May be `null` for paths that appear before any section header in the file.
+  /// In that case, the section always applies.
+  final Expression _condition;
+  final List<StatusEntry> entries = [];
+
+  /// Returns true if this section should apply in the given [environment].
+  bool isEnabled(Map<String, dynamic> environment) =>
+      _condition == null || _condition.evaluate(environment);
+
+  StatusSection(this._condition);
+}
+
+/// Describes the test status of the file or files at a given path.
+class StatusEntry {
+  final String path;
+  final List<Expectation> expectations;
+  final int issue;
+
+  StatusEntry(this.path, this.expectations, this.issue);
+}