Roll Observatory deps (charted -> ^0.3.0)

packages/dart_style/lib/src/rule/metadata.dart

+// Copyright (c) 2015, 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 dart_style.src.rule.metadata;
+
+import 'argument.dart';
+import 'rule.dart';
+
+/// Rule for handling splits between parameter metadata annotations and the
+/// following parameter.
+///
+/// Metadata annotations for parameters (and type parameters) get some special
+/// handling. We use a single rule for all annotations in the parameter list.
+/// If any of the annotations split, they all do.
+///
+/// Also, if the annotations split, we force the entire parameter list to fully
+/// split, both named and positional.
+class MetadataRule extends Rule {
+  Rule _positionalRule;
+  Rule _namedRule;
+
+  /// Remembers that [rule] is the [PositionalRule] used by the argument list
+  /// containing the parameter metadata using this rule.
+  void bindPositionalRule(PositionalRule rule) {
+    _positionalRule = rule;
+  }
+
+  /// Remembers that [rule] is the [NamedRule] used by the argument list
+  /// containing the parameter metadata using this rule.
+  void bindNamedRule(NamedRule rule) {
+    _namedRule = rule;
+  }
+
+  /// Constrains the surrounding argument list rules to fully split if the
+  /// metadata does.
+  int constrain(int value, Rule other) {
+    var constrained = super.constrain(value, other);
+    if (constrained != null) return constrained;
+
+    // If the metadata doesn't split, we don't care what the arguments do.
+    if (value == Rule.unsplit) return null;
+
+    // Otherwise, they have to split.
+    if (other == _positionalRule) return _positionalRule.fullySplitValue;
+    if (other == _namedRule) return _namedRule.fullySplitValue;
+
+    return null;
+  }
+
+  void addConstrainedRules(Set<Rule> rules) {
+    if (_positionalRule != null) rules.add(_positionalRule);
+    if (_namedRule != null) rules.add(_namedRule);
+  }
+
+  void forgetUnusedRules() {
+    super.forgetUnusedRules();
+    if (_positionalRule != null && _positionalRule.index == null) {
+      _positionalRule = null;
+    }
+
+    if (_namedRule != null && _namedRule.index == null) {
+      _namedRule = null;
+    }
+  }
+}