Classes List

Symfony\Component\ExpressionLanguage\Parser

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<?php

/* * This file is part of the Symfony package. * * (c) Fabien Potencier <fabien@symfony.com> * * For the full copyright and license information, please view the LICENSE * file that was distributed with this source code. */


namespace Symfony\Component\ExpressionLanguage;

/** * Parsers a token stream. * * This parser implements a "Precedence climbing" algorithm. * * @see http://www.engr.mun.ca/~theo/Misc/exp_parsing.htm * @see http://en.wikipedia.org/wiki/Operator-precedence_parser * * @author Fabien Potencier <fabien@symfony.com> */
class Parser
{
    const OPERATOR_LEFT = 1;
    const OPERATOR_RIGHT = 2;

    private $stream;
    private $unaryOperators;
    private $binaryOperators;
    private $functions;
    private $names;

    public function __construct(array $functions)
    {
        $this->functions = $functions;

        $this->unaryOperators = array(
            'not' => array('precedence' => 50),
            '!' => array('precedence' => 50),
            '-' => array('precedence' => 500),
            '+' => array('precedence' => 500),
        );
        $this->binaryOperators = array(
            'or' => array('precedence' => 10'associativity' => self::OPERATOR_LEFT),
            '||' => array('precedence' => 10'associativity' => self::OPERATOR_LEFT),
            'and' => array('precedence' => 15'associativity' => self::OPERATOR_LEFT),
            '&&' => array('precedence' => 15'associativity' => self::OPERATOR_LEFT),
            '|' => array('precedence' => 16'associativity' => self::OPERATOR_LEFT),
            '^' => array('precedence' => 17'associativity' => self::OPERATOR_LEFT),
            '&' => array('precedence' => 18'associativity' => self::OPERATOR_LEFT),
            '==' => array('precedence' => 20'associativity' => self::OPERATOR_LEFT),
            '===' => array('precedence' => 20'associativity' => self::OPERATOR_LEFT),
            '!=' => array('precedence' => 20'associativity' => self::OPERATOR_LEFT),
            '!==' => array('precedence' => 20'associativity' => self::OPERATOR_LEFT),
            '<' => array('precedence' => 20'associativity' => self::OPERATOR_LEFT),
            '>' => array('precedence' => 20'associativity' => self::OPERATOR_LEFT),
            '>=' => array('precedence' => 20'associativity' => self::OPERATOR_LEFT),
            '<=' => array('precedence' => 20'associativity' => self::OPERATOR_LEFT),
            'not in' => array('precedence' => 20'associativity' => self::OPERATOR_LEFT),
            'in' => array('precedence' => 20'associativity' => self::OPERATOR_LEFT),
            'matches' => array('precedence' => 20'associativity' => self::OPERATOR_LEFT),
            '..' => array('precedence' => 25'associativity' => self::OPERATOR_LEFT),
            '+' => array('precedence' => 30'associativity' => self::OPERATOR_LEFT),
            '-' => array('precedence' => 30'associativity' => self::OPERATOR_LEFT),
            '~' => array('precedence' => 40'associativity' => self::OPERATOR_LEFT),
            '*' => array('precedence' => 60'associativity' => self::OPERATOR_LEFT),
            '/' => array('precedence' => 60'associativity' => self::OPERATOR_LEFT),
            '%' => array('precedence' => 60'associativity' => self::OPERATOR_LEFT),
            '**' => array('precedence' => 200'associativity' => self::OPERATOR_RIGHT),
        );
    }

    /** * Converts a token stream to a node tree. * * The valid names is an array where the values * are the names that the user can use in an expression. * * If the variable name in the compiled PHP code must be * different, define it as the key. * * For instance, ['this' => 'container'] means that the * variable 'container' can be used in the expression * but the compiled code will use 'this'. * * @param TokenStream $stream A token stream instance * @param array $names An array of valid names * * @return Node\Node A node tree * * @throws SyntaxError */
    public function parse(TokenStream $stream$names = array())
    {
        $this->stream = $stream;
        $this->names = $names;

        $node = $this->parseExpression();
        if (!$stream->isEOF()) {
            throw new SyntaxError(sprintf('Unexpected token "%s" of value "%s"'$stream->current->type$stream->current->value), $stream->current->cursor$stream->getExpression());
        }

        return $node;
    }

    public function parseExpression($precedence = 0)
    {
        $expr = $this->getPrimary();
        $token = $this->stream->current;
        while ($token->test(Token::OPERATOR_TYPE&& isset($this->binaryOperators[$token->value]) && $this->binaryOperators[$token->value]['precedence'>= $precedence) {
            $op = $this->binaryOperators[$token->value];
            $this->stream->next();

            $expr1 = $this->parseExpression(self::OPERATOR_LEFT === $op['associativity'] ? $op['precedence'] + 1 : $op['precedence']);
            $expr = new Node\BinaryNode($token->value$expr$expr1);

            $token = $this->stream->current;
        }

        if (0 === $precedence) {
            return $this->parseConditionalExpression($expr);
        }

        return $expr;
    }

    protected function getPrimary()
    {
        $token = $this->stream->current;

        if ($token->test(Token::OPERATOR_TYPE&& isset($this->unaryOperators[$token->value])) {
            $operator = $this->unaryOperators[$token->value];
            $this->stream->next();
            $expr = $this->parseExpression($operator['precedence']);

            return $this->parsePostfixExpression(new Node\UnaryNode($token->value$expr));
        }

        if ($token->test(Token::PUNCTUATION_TYPE'(')) {
            $this->stream->next();
            $expr = $this->parseExpression();
            $this->stream->expect(Token::PUNCTUATION_TYPE')''An opened parenthesis is not properly closed');

            return $this->parsePostfixExpression($expr);
        }

        return $this->parsePrimaryExpression();
    }

    protected function parseConditionalExpression($expr)
    {
        while ($this->stream->current->test(Token::PUNCTUATION_TYPE'?')) {
            $this->stream->next();
            if (!$this->stream->current->test(Token::PUNCTUATION_TYPE':')) {
                $expr2 = $this->parseExpression();
                if ($this->stream->current->test(Token::PUNCTUATION_TYPE':')) {
                    $this->stream->next();
                    $expr3 = $this->parseExpression();
                } else {
                    $expr3 = new Node\ConstantNode(null);
                }
            } else {
                $this->stream->next();
                $expr2 = $expr;
                $expr3 = $this->parseExpression();
            }

            $expr = new Node\ConditionalNode($expr$expr2$expr3);
        }

        return $expr;
    }

    public function parsePrimaryExpression()
    {
        $token = $this->stream->current;
        switch ($token->type) {
            case Token::NAME_TYPE:
                $this->stream->next();
                switch ($token->value) {
                    case 'true':
                    case 'TRUE':
                        return new Node\ConstantNode(true);

                    case 'false':
                    case 'FALSE':
                        return new Node\ConstantNode(false);

                    case 'null':
                    case 'NULL':
                        return new Node\ConstantNode(null);

                    default:
                        if ('(' === $this->stream->current->value) {
                            if (false === isset($this->functions[$token->value])) {
                                throw new SyntaxError(sprintf('The function "%s" does not exist'$token->value), $token->cursor$this->stream->getExpression(), $token->valuearray_keys($this->functions));
                            }

                            $node = new Node\FunctionNode($token->value$this->parseArguments());
                        } else {
                            if (!in_array($token->value$this->namestrue)) {
                                throw new SyntaxError(sprintf('Variable "%s" is not valid'$token->value), $token->cursor$this->stream->getExpression(), $token->value$this->names);
                            }

                            // is the name used in the compiled code different
                            // from the name used in the expression?
                            if (is_int($name = array_search($token->value$this->names))) {
                                $name = $token->value;
                            }

                            $node = new Node\NameNode($name);
                        }
                }
                break;

            case Token::NUMBER_TYPE:
            case Token::STRING_TYPE:
                $this->stream->next();

                return new Node\ConstantNode($token->value);

            default:
                if ($token->test(Token::PUNCTUATION_TYPE'[')) {
                    $node = $this->parseArrayExpression();
                } elseif ($token->test(Token::PUNCTUATION_TYPE'{')) {
                    $node = $this->parseHashExpression();
                } else {
                    throw new SyntaxError(sprintf('Unexpected token "%s" of value "%s"'$token->type$token->value), $token->cursor$this->stream->getExpression());
                }
        }

        return $this->parsePostfixExpression($node);
    }

    public function parseArrayExpression()
    {
        $this->stream->expect(Token::PUNCTUATION_TYPE'[''An array element was expected');

        $node = new Node\ArrayNode();
        $first = true;
        while (!$this->stream->current->test(Token::PUNCTUATION_TYPE']')) {
            if (!$first) {
                $this->stream->expect(Token::PUNCTUATION_TYPE',''An array element must be followed by a comma');

                // trailing ,?
                if ($this->stream->current->test(Token::PUNCTUATION_TYPE']')) {
                    break;
                }
            }
            $first = false;

            $node->addElement($this->parseExpression());
        }
        $this->stream->expect(Token::PUNCTUATION_TYPE']''An opened array is not properly closed');

        return $node;
    }

    public function parseHashExpression()
    {
        $this->stream->expect(Token::PUNCTUATION_TYPE'{''A hash element was expected');

        $node = new Node\ArrayNode();
        $first = true;
        while (!$this->stream->current->test(Token::PUNCTUATION_TYPE'}')) {
            if (!$first) {
                $this->stream->expect(Token::PUNCTUATION_TYPE',''A hash value must be followed by a comma');

                // trailing ,?
                if ($this->stream->current->test(Token::PUNCTUATION_TYPE'}')) {
                    break;
                }
            }
            $first = false;

            // a hash key can be:
            //
            // * a number -- 12
            // * a string -- 'a'
            // * a name, which is equivalent to a string -- a
            // * an expression, which must be enclosed in parentheses -- (1 + 2)
            if ($this->stream->current->test(Token::STRING_TYPE|| $this->stream->current->test(Token::NAME_TYPE|| $this->stream->current->test(Token::NUMBER_TYPE)) {
                $key = new Node\ConstantNode($this->stream->current->value);
                $this->stream->next();
            } elseif ($this->stream->current->test(Token::PUNCTUATION_TYPE'(')) {
                $key = $this->parseExpression();
            } else {
                $current = $this->stream->current;

                throw new SyntaxError(sprintf('A hash key must be a quoted string, a number, a name, or an expression enclosed in parentheses (unexpected token "%s" of value "%s"'$current->type$current->value), $current->cursor$this->stream->getExpression());
            }

            $this->stream->expect(Token::PUNCTUATION_TYPE':''A hash key must be followed by a colon (:)');
            $value = $this->parseExpression();

            $node->addElement($value$key);
        }
        $this->stream->expect(Token::PUNCTUATION_TYPE'}''An opened hash is not properly closed');

        return $node;
    }

    public function parsePostfixExpression($node)
    {
        $token = $this->stream->current;
        while (Token::PUNCTUATION_TYPE == $token->type) {
            if ('.' === $token->value) {
                $this->stream->next();
                $token = $this->stream->current;
                $this->stream->next();

                if (
                    Token::NAME_TYPE !== $token->type
                    &&
                    // Operators like "not" and "matches" are valid method or property names,
                    //
                    // In other words, besides NAME_TYPE, OPERATOR_TYPE could also be parsed as a property or method.
                    // This is because operators are processed by the lexer prior to names. So "not" in "foo.not()" or "matches" in "foo.matches" will be recognized as an operator first.
                    // But in fact, "not" and "matches" in such expressions shall be parsed as method or property names.
                    //
                    // And this ONLY works if the operator consists of valid characters for a property or method name.
                    //
                    // Other types, such as STRING_TYPE and NUMBER_TYPE, can't be parsed as property nor method names.
                    //
                    // As a result, if $token is NOT an operator OR $token->value is NOT a valid property or method name, an exception shall be thrown.
                    (Token::OPERATOR_TYPE !== $token->type || !preg_match('/[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*/A'$token->value))
                ) {
                    throw new SyntaxError('Expected name'$token->cursor$this->stream->getExpression());
                }

                $arg = new Node\ConstantNode($token->valuetrue);

                $arguments = new Node\ArgumentsNode();
                if ($this->stream->current->test(Token::PUNCTUATION_TYPE'(')) {
                    $type = Node\GetAttrNode::METHOD_CALL;
                    foreach ($this->parseArguments()->nodes as $n) {
                        $arguments->addElement($n);
                    }
                } else {
                    $type = Node\GetAttrNode::PROPERTY_CALL;
                }

                $node = new Node\GetAttrNode($node$arg$arguments$type);
            } elseif ('[' === $token->value) {
                $this->stream->next();
                $arg = $this->parseExpression();
                $this->stream->expect(Token::PUNCTUATION_TYPE']');

                $node = new Node\GetAttrNode($node$argnew Node\ArgumentsNode(), Node\GetAttrNode::ARRAY_CALL);
            } else {
                break;
            }

            $token = $this->stream->current;
        }

        return $node;
    }

    /** * Parses arguments. */
    public function parseArguments()
    {
        $args = array();
        $this->stream->expect(Token::PUNCTUATION_TYPE'(''A list of arguments must begin with an opening parenthesis');
        while (!$this->stream->current->test(Token::PUNCTUATION_TYPE')')) {
            if (!empty($args)) {
                $this->stream->expect(Token::PUNCTUATION_TYPE',''Arguments must be separated by a comma');
            }

            $args[] = $this->parseExpression();
        }
        $this->stream->expect(Token::PUNCTUATION_TYPE')''A list of arguments must be closed by a parenthesis');

        return new Node\Node($args);
    }
}