Revert "Refactor and clean up the status file parsing code."

tools/testing/dart/status_expression.dart

Index: tools/testing/dart/status_expression.dart
diff --git a/tools/testing/dart/status_expression.dart b/tools/testing/dart/status_expression.dart
index d99bef45d321f3cd0a245d1ea6990f04fcf4c4b5..3804d1daecb47f829a67aab2364539b2685bd7dc 100644
--- a/tools/testing/dart/status_expression.dart
+++ b/tools/testing/dart/status_expression.dart
@@ -2,232 +2,313 @@
 // 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.
 
-/// A parsed Boolean expression AST.
-abstract class Expression {
-  /// Parses Boolean expressions in a .status file for Dart.
-  ///
-  /// The grammar is:
-  ///
-  ///     expression := or
-  ///     or         := and ( "||" and )*
-  ///     and        := primary ( "&&" primary )*
-  ///     primary    := "$" identifier ( ( "==" | "!=" ) identifier )? |
-  ///                   "(" expression ")"
-  ///     identifier := regex "\w+"
-  ///
-  /// Expressions evaluate as expected, with values of variables found in an
-  /// environment passed to the evaluator.
-  static Expression parse(String expression) =>
-      new _ExpressionParser(expression).parse();
-
-  /// Evaluates the expression where all variables are defined by the given
-  /// [environment].
-  bool evaluate(Map<String, dynamic> environment);
+library status_expression;
+
+/**
+ * Parse and evaluate expressions in a .status file for Dart and V8.
+ * There are set expressions and Boolean expressions in a .status file.
+ * The grammar is:
+ *   BooleanExpression := $variableName == value | $variableName != value |
+ *                        $variableName | (BooleanExpression) |
+ *                        BooleanExpression && BooleanExpression |
+ *                        BooleanExpression || BooleanExpression
+ *
+ *   SetExpression := value | (SetExpression) |
+ *                    SetExpression || SetExpression |
+ *                    SetExpression if BooleanExpression |
+ *                    SetExpression , SetExpression
+ *
+ *  Productions are listed in order of precedence, and the || and , operators
+ *  both evaluate to set union, but with different precedence.
+ *
+ *  Values and variableNames are non-empty strings of word characters, matching
+ *  the RegExp \w+.
+ *
+ *  Expressions evaluate as expected, with values of variables found in
+ *  an environment passed to the evaluator.  The SetExpression "value"
+ *  evaluates to a singleton set containing that value. "A if B" evaluates
+ *  to A if B is true, and to the empty set if B is false.
+ */
+
+class ExprEvaluationException {
+  String error;
+
+  ExprEvaluationException(this.error);
+
+  toString() => error;
 }
 
-/// Keyword token strings.
-class _Token {
-  static const leftParen = "(";
-  static const rightParen = ")";
-  static const dollar = r"$";
-  static const equals = "==";
-  static const notEqual = "!=";
-  static const and = "&&";
-  static const or = "||";
+class Token {
+  static const String LEFT_PAREN = "(";
+  static const String RIGHT_PAREN = ")";
+  static const String DOLLAR_SYMBOL = r"$";
+  static const String UNION = ",";
+  static const String EQUALS = "==";
+  static const String NOT_EQUALS = "!=";
+  static const String AND = "&&";
+  static const String OR = "||";
 }
 
-/// A reference to a variable.
-class _Variable {
-  final String name;
+class Tokenizer {
+  String expression;
+  List<String> tokens;
 
-  _Variable(this.name);
+  Tokenizer(String this.expression) : tokens = new List<String>();
 
-  dynamic lookup(Map<String, dynamic> environment) {
-    var value = environment[name];
-    if (value == null) {
-      throw new Exception("Could not find '$name' in environment "
-          "while evaluating status file expression.");
-    }
+  // Tokens are : "(", ")", "$", ",", "&&", "||", "==", "!=", and (maximal) \w+.
+  static final testRegexp =
+      new RegExp(r"^([()$\w\s,]|(\&\&)|(\|\|)|(\=\=)|(\!\=))+$");
+  static final regexp = new RegExp(r"[()$,]|(\&\&)|(\|\|)|(\=\=)|(\!\=)|\w+");
 
-    return value;
+  List<String> tokenize() {
+    if (!testRegexp.hasMatch(expression)) {
+      throw new FormatException("Syntax error in '$expression'");
+    }
+    for (Match match in regexp.allMatches(expression)) tokens.add(match[0]);
+    return tokens;
   }
 }
 
-/// Tests whether a given variable is or is not equal some literal value, as in:
-///
-///     $variable == someValue
-class _ComparisonExpression implements Expression {
-  final _Variable left;
-  final String right;
-  final bool negate;
+abstract class BooleanExpression {
+  bool evaluate(Map<String, String> environment);
+}
+
+abstract class SetExpression {
+  Set<String> evaluate(Map<String, String> environment);
+}
+
+class Comparison implements BooleanExpression {
+  TermVariable left;
+  TermConstant right;
+  bool negate;
 
-  _ComparisonExpression(this.left, this.right, this.negate);
+  Comparison(this.left, this.right, this.negate);
 
-  bool evaluate(Map<String, dynamic> environment) {
-    return negate != (left.lookup(environment) == right);
+  bool evaluate(environment) {
+    return negate !=
+        (left.termValue(environment) == right.termValue(environment));
   }
 
-  String toString() => "(\$${left.name} ${negate ? '!=' : '=='} $right)";
+  String toString() =>
+      "(\$${left.name} ${negate ? '!=' : '=='} ${right.value})";
+}
+
+class TermVariable {
+  String name;
+
+  TermVariable(this.name);
+
+  String termValue(environment) {
+    var value = environment[name];
+    if (value == null) {
+      throw new ExprEvaluationException("Could not find '$name' in environment "
+          "while evaluating status file expression.");
+    }
+    return value.toString();
+  }
 }
 
-/// A reference to a variable defined in the environment. The variable's value
-/// should be Boolean and the expression is true when the value is "true".
-///
-///     $variable
-class _VariableExpression implements Expression {
-  final _Variable variable;
+class TermConstant {
+  String value;
+
+  TermConstant(String this.value);
 
-  _VariableExpression(this.variable);
+  String termValue(environment) => value;
+}
+
+class BooleanVariable implements BooleanExpression {
+  TermVariable variable;
 
-  bool evaluate(Map<String, dynamic> environment) =>
-      variable.lookup(environment) == 'true';
+  BooleanVariable(this.variable);
 
+  bool evaluate(environment) => variable.termValue(environment) == 'true';
   String toString() => "(bool \$${variable.name})";
 }
 
-/// A logical `||` or `&&` expression.
-class _LogicExpression implements Expression {
-  /// The operator, `||` or `&&`.
-  final String op;
-
-  final Expression left;
-  final Expression right;
+class BooleanOperation implements BooleanExpression {
+  String op;
+  BooleanExpression left;
+  BooleanExpression right;
 
-  _LogicExpression(this.op, this.left, this.right);
+  BooleanOperation(this.op, this.left, this.right);
 
-  bool evaluate(Map<String, dynamic> environment) => (op == _Token.and)
+  bool evaluate(environment) => (op == Token.AND)
       ? left.evaluate(environment) && right.evaluate(environment)
       : left.evaluate(environment) || right.evaluate(environment);
-
   String toString() => "($left $op $right)";
 }
 
-/// Parser for Boolean expressions in a .status file for Dart.
-class _ExpressionParser {
-  final _Scanner _scanner;
-
-  _ExpressionParser(String expression) : _scanner = new _Scanner(expression);
-
-  Expression parse() {
-    var expression = _parseOr();
+class SetUnion implements SetExpression {
+  SetExpression left;
+  SetExpression right;
 
-    // Should consume entire string.
-    if (_scanner.hasMore) {
-      throw new FormatException("Unexpected input after expression");
-    }
+  SetUnion(this.left, this.right);
 
-    return expression;
+  // Overwrites left.evaluate(env).
+  // Set.addAll does not return this.
+  Set<String> evaluate(environment) {
+    Set<String> result = left.evaluate(environment);
+    result.addAll(right.evaluate(environment));
+    return result;
   }
 
-  Expression _parseOr() {
-    var left = _parseAnd();
-    while (_scanner.match(_Token.or)) {
-      var right = _parseAnd();
-      left = new _LogicExpression(_Token.or, left, right);
-    }
-
-    return left;
-  }
+  String toString() => "($left || $right)";
+}
 
-  Expression _parseAnd() {
-    var left = _parsePrimary();
-    while (_scanner.match(_Token.and)) {
-      var right = _parsePrimary();
-      left = new _LogicExpression(_Token.and, left, right);
-    }
+class SetIf implements SetExpression {
+  SetExpression left;
+  BooleanExpression right;
 
-    return left;
-  }
+  SetIf(this.left, this.right);
 
-  Expression _parsePrimary() {
-    if (_scanner.match(_Token.leftParen)) {
-      var value = _parseOr();
-      if (!_scanner.match(_Token.rightParen)) {
-        throw new FormatException("Missing right parenthesis in expression");
-      }
+  Set<String> evaluate(environment) => right.evaluate(environment)
+      ? left.evaluate(environment)
+      : new Set<String>();
+  String toString() => "($left if $right)";
+}
 
-      return value;
-    }
+class SetConstant implements SetExpression {
+  String value;
 
-    // The only atomic booleans are of the form $variable == value or
-    // of the form $variable.
-    if (!_scanner.match(_Token.dollar)) {
-      throw new FormatException(
-          "Expected \$ in expression, got ${_scanner.current}");
-    }
+  SetConstant(String v) : value = v.toLowerCase();
 
-    if (!_scanner.isIdentifier) {
-      throw new FormatException(
-          "Expected identifier in expression, got ${_scanner.current}");
-    }
+  Set<String> evaluate(environment) => [value].toSet();
+  String toString() => value;
+}
 
-    var left = new _Variable(_scanner.current);
-    _scanner.advance();
+// An iterator that allows peeking at the current token.
+class Scanner {
+  List<String> tokens;
+  Iterator tokenIterator;
+  String current;
 
-    if (_scanner.current == _Token.equals ||
-        _scanner.current == _Token.notEqual) {
-      var negate = _scanner.advance() == _Token.notEqual;
+  Scanner(this.tokens) {
+    tokenIterator = tokens.iterator;
+    advance();
+  }
 
-      if (!_scanner.isIdentifier) {
-        throw new FormatException(
-            "Expected value in expression, got ${_scanner.current}");
-      }
+  bool hasMore() => current != null;
 
-      var right = _scanner.advance();
-      return new _ComparisonExpression(left, right, negate);
-    } else {
-      return new _VariableExpression(left);
-    }
+  void advance() {
+    current = tokenIterator.moveNext() ? tokenIterator.current : null;
   }
 }
 
-/// An iterator that allows peeking at the current token.
-class _Scanner {
-  /// Tokens are "(", ")", "$", "&&", "||", "==", "!=", and (maximal) \w+.
-  static final _testPattern =
-      new RegExp(r"^([()$\w\s]|(\&\&)|(\|\|)|(\=\=)|(\!\=))+$");
-  static final _tokenPattern =
-      new RegExp(r"[()$]|(\&\&)|(\|\|)|(\=\=)|(\!\=)|\w+");
-
-  static final _identifierPattern = new RegExp(r"^\w+$");
+class ExpressionParser {
+  Scanner scanner;
 
-  /// The token strings being iterated.
-  final Iterator<String> tokenIterator;
+  ExpressionParser(this.scanner);
 
-  String current;
+  SetExpression parseSetExpression() => parseSetUnion();
 
-  _Scanner(String expression) : tokenIterator = tokenize(expression).iterator {
-    advance();
+  SetExpression parseSetUnion() {
+    SetExpression left = parseSetIf();
+    while (scanner.hasMore() && scanner.current == Token.UNION) {
+      scanner.advance();
+      SetExpression right = parseSetIf();
+      left = new SetUnion(left, right);
+    }
+    return left;
   }
 
-  static List<String> tokenize(String expression) {
-    if (!_testPattern.hasMatch(expression)) {
-      throw new FormatException("Syntax error in '$expression'");
+  SetExpression parseSetIf() {
+    SetExpression left = parseSetOr();
+    while (scanner.hasMore() && scanner.current == "if") {
+      scanner.advance();
+      BooleanExpression right = parseBooleanExpression();
+      left = new SetIf(left, right);
     }
+    return left;
+  }
 
-    return _tokenPattern
-        .allMatches(expression)
-        .map((match) => match[0])
-        .toList();
+  SetExpression parseSetOr() {
+    SetExpression left = parseSetAtomic();
+    while (scanner.hasMore() && scanner.current == Token.OR) {
+      scanner.advance();
+      SetExpression right = parseSetAtomic();
+      left = new SetUnion(left, right);
+    }
+    return left;
   }
 
-  bool get hasMore => current != null;
+  SetExpression parseSetAtomic() {
+    if (scanner.current == Token.LEFT_PAREN) {
+      scanner.advance();
+      SetExpression value = parseSetExpression();
+      if (scanner.current != Token.RIGHT_PAREN) {
+        throw new FormatException("Missing right parenthesis in expression");
+      }
+      scanner.advance();
+      return value;
+    }
+    if (!new RegExp(r"^\w+$").hasMatch(scanner.current)) {
+      throw new FormatException(
+          "Expected identifier in expression, got ${scanner.current}");
+    }
+    SetExpression value = new SetConstant(scanner.current);
+    scanner.advance();
+    return value;
+  }
 
-  /// Returns `true` if the current token is an identifier.
-  bool get isIdentifier => _identifierPattern.hasMatch(current);
+  BooleanExpression parseBooleanExpression() => parseBooleanOr();
 
-  /// If the current token is [token], consumes it and returns `true`.
-  bool match(String token) {
-    if (!hasMore || current != token) return false;
+  BooleanExpression parseBooleanOr() {
+    BooleanExpression left = parseBooleanAnd();
+    while (scanner.hasMore() && scanner.current == Token.OR) {
+      scanner.advance();
+      BooleanExpression right = parseBooleanAnd();
+      left = new BooleanOperation(Token.OR, left, right);
+    }
+    return left;
+  }
 
-    advance();
-    return true;
+  BooleanExpression parseBooleanAnd() {
+    BooleanExpression left = parseBooleanAtomic();
+    while (scanner.hasMore() && scanner.current == Token.AND) {
+      scanner.advance();
+      BooleanExpression right = parseBooleanAtomic();
+      left = new BooleanOperation(Token.AND, left, right);
+    }
+    return left;
   }
 
-  /// Consumes the current token and returns it.
-  String advance() {
-    var previous = current;
-    current = tokenIterator.moveNext() ? tokenIterator.current : null;
-    return previous;
+  BooleanExpression parseBooleanAtomic() {
+    if (scanner.current == Token.LEFT_PAREN) {
+      scanner.advance();
+      BooleanExpression value = parseBooleanExpression();
+      if (scanner.current != Token.RIGHT_PAREN) {
+        throw new FormatException("Missing right parenthesis in expression");
+      }
+      scanner.advance();
+      return value;
+    }
+
+    // The only atomic booleans are of the form $variable == value or
+    // of the form $variable.
+    if (scanner.current != Token.DOLLAR_SYMBOL) {
+      throw new FormatException(
+          "Expected \$ in expression, got ${scanner.current}");
+    }
+    scanner.advance();
+    if (!new RegExp(r"^\w+$").hasMatch(scanner.current)) {
+      throw new FormatException(
+          "Expected identifier in expression, got ${scanner.current}");
+    }
+    TermVariable left = new TermVariable(scanner.current);
+    scanner.advance();
+    if (scanner.current == Token.EQUALS ||
+        scanner.current == Token.NOT_EQUALS) {
+      bool negate = scanner.current == Token.NOT_EQUALS;
+      scanner.advance();
+      if (!new RegExp(r"^\w+$").hasMatch(scanner.current)) {
+        throw new FormatException(
+            "Expected value in expression, got ${scanner.current}");
+      }
+      TermConstant right = new TermConstant(scanner.current);
+      scanner.advance();
+      return new Comparison(left, right, negate);
+    } else {
+      return new BooleanVariable(left);
+    }
   }
 }