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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
{
public const OPERATOR_LEFT = 1;
public const OPERATOR_RIGHT = 2;
private $stream;
private $unaryOperators;
private $binaryOperators;
private $functions;
private $names;
private $lint;
public function __construct(array $functions)
{
$this->functions = $functions;
$this->unaryOperators = [
'not' => ['precedence' => 50],
'!' => ['precedence' => 50],
'-' => ['precedence' => 500],
'+' => ['precedence' => 500],
];
$this->binaryOperators = [
'or' => ['precedence' => 10, 'associativity' => self::OPERATOR_LEFT],
'||' => ['precedence' => 10, 'associativity' => self::OPERATOR_LEFT],
'and' => ['precedence' => 15, 'associativity' => self::OPERATOR_LEFT],
'&&' => ['precedence' => 15, 'associativity' => self::OPERATOR_LEFT],
'|' => ['precedence' => 16, 'associativity' => self::OPERATOR_LEFT],
'^' => ['precedence' => 17, 'associativity' => self::OPERATOR_LEFT],
'&' => ['precedence' => 18, 'associativity' => self::OPERATOR_LEFT],
'==' => ['precedence' => 20, 'associativity' => self::OPERATOR_LEFT],
'===' => ['precedence' => 20, 'associativity' => self::OPERATOR_LEFT],
'!=' => ['precedence' => 20, 'associativity' => self::OPERATOR_LEFT],
'!==' => ['precedence' => 20, 'associativity' => self::OPERATOR_LEFT],
'<' => ['precedence' => 20, 'associativity' => self::OPERATOR_LEFT],
'>' => ['precedence' => 20, 'associativity' => self::OPERATOR_LEFT],
'>=' => ['precedence' => 20, 'associativity' => self::OPERATOR_LEFT],
'<=' => ['precedence' => 20, 'associativity' => self::OPERATOR_LEFT],
'not in' => ['precedence' => 20, 'associativity' => self::OPERATOR_LEFT],
'in' => ['precedence' => 20, 'associativity' => self::OPERATOR_LEFT],
'matches' => ['precedence' => 20, 'associativity' => self::OPERATOR_LEFT],
'..' => ['precedence' => 25, 'associativity' => self::OPERATOR_LEFT],
'+' => ['precedence' => 30, 'associativity' => self::OPERATOR_LEFT],
'-' => ['precedence' => 30, 'associativity' => self::OPERATOR_LEFT],
'~' => ['precedence' => 40, 'associativity' => self::OPERATOR_LEFT],
'*' => ['precedence' => 60, 'associativity' => self::OPERATOR_LEFT],
'/' => ['precedence' => 60, 'associativity' => self::OPERATOR_LEFT],
'%' => ['precedence' => 60, 'associativity' => self::OPERATOR_LEFT],
'**' => ['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'.
*
* @return Node\Node
*
* @throws SyntaxError
*/
public function parse(TokenStream $stream, array $names = [])
{
$this->lint = false;
return $this->doParse($stream, $names);
}
/**
* Validates the syntax of an expression.
*
* The syntax of the passed expression will be checked, but not parsed.
* If you want to skip checking dynamic variable names, pass `null` instead of the array.
*
* @throws SyntaxError When the passed expression is invalid
*/
public function lint(TokenStream $stream, ?array $names = []): void
{
$this->lint = true;
$this->doParse($stream, $names);
}
/**
* @throws SyntaxError
*/
private function doParse(TokenStream $stream, ?array $names = []): Node\Node
{
$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());
}
$this->stream = null;
$this->names = null;
return $node;
}
public function parseExpression(int $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(Node\Node $expr)
{
while ($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(), $token->value, array_keys($this->functions));
}
$node = new Node\FunctionNode($token->value, $this->parseArguments());
} else {
if (!$this->lint || \is_array($this->names)) {
if (!\in_array($token->value, $this->names, true)) {
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;
}
} else {
$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\Node $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->value, true);
$arguments = new Node\ArgumentsNode();
if ($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, $arg, new Node\ArgumentsNode(), Node\GetAttrNode::ARRAY_CALL);
} else {
break;
}
$token = $this->stream->current;
}
return $node;
}
/**
* Parses arguments.
*/
public function parseArguments()
{
$args = [];
$this->stream->expect(Token::PUNCTUATION_TYPE, '(', 'A list of arguments must begin with an opening parenthesis');
while (!$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);
}
}