235 lines
9.2 KiB
PHP
235 lines
9.2 KiB
PHP
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<?php declare(strict_types=1);
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namespace PhpParser;
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use PhpParser\Node\Expr;
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use PhpParser\Node\Scalar;
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use function array_merge;
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/**
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* Evaluates constant expressions.
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*
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* This evaluator is able to evaluate all constant expressions (as defined by PHP), which can be
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* evaluated without further context. If a subexpression is not of this type, a user-provided
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* fallback evaluator is invoked. To support all constant expressions that are also supported by
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* PHP (and not already handled by this class), the fallback evaluator must be able to handle the
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* following node types:
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*
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* * All Scalar\MagicConst\* nodes.
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* * Expr\ConstFetch nodes. Only null/false/true are already handled by this class.
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* * Expr\ClassConstFetch nodes.
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*
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* The fallback evaluator should throw ConstExprEvaluationException for nodes it cannot evaluate.
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*
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* The evaluation is dependent on runtime configuration in two respects: Firstly, floating
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* point to string conversions are affected by the precision ini setting. Secondly, they are also
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* affected by the LC_NUMERIC locale.
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*/
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class ConstExprEvaluator {
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/** @var callable|null */
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private $fallbackEvaluator;
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/**
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* Create a constant expression evaluator.
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*
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* The provided fallback evaluator is invoked whenever a subexpression cannot be evaluated. See
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* class doc comment for more information.
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*
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* @param callable|null $fallbackEvaluator To call if subexpression cannot be evaluated
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*/
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public function __construct(?callable $fallbackEvaluator = null) {
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$this->fallbackEvaluator = $fallbackEvaluator ?? function (Expr $expr) {
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throw new ConstExprEvaluationException(
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"Expression of type {$expr->getType()} cannot be evaluated"
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);
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};
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}
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/**
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* Silently evaluates a constant expression into a PHP value.
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*
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* Thrown Errors, warnings or notices will be converted into a ConstExprEvaluationException.
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* The original source of the exception is available through getPrevious().
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*
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* If some part of the expression cannot be evaluated, the fallback evaluator passed to the
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* constructor will be invoked. By default, if no fallback is provided, an exception of type
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* ConstExprEvaluationException is thrown.
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*
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* See class doc comment for caveats and limitations.
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*
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* @param Expr $expr Constant expression to evaluate
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* @return mixed Result of evaluation
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*
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* @throws ConstExprEvaluationException if the expression cannot be evaluated or an error occurred
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*/
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public function evaluateSilently(Expr $expr) {
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set_error_handler(function ($num, $str, $file, $line) {
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throw new \ErrorException($str, 0, $num, $file, $line);
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});
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try {
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return $this->evaluate($expr);
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} catch (\Throwable $e) {
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if (!$e instanceof ConstExprEvaluationException) {
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$e = new ConstExprEvaluationException(
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"An error occurred during constant expression evaluation", 0, $e);
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}
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throw $e;
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} finally {
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restore_error_handler();
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}
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}
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/**
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* Directly evaluates a constant expression into a PHP value.
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*
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* May generate Error exceptions, warnings or notices. Use evaluateSilently() to convert these
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* into a ConstExprEvaluationException.
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*
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* If some part of the expression cannot be evaluated, the fallback evaluator passed to the
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* constructor will be invoked. By default, if no fallback is provided, an exception of type
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* ConstExprEvaluationException is thrown.
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*
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* See class doc comment for caveats and limitations.
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*
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* @param Expr $expr Constant expression to evaluate
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* @return mixed Result of evaluation
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*
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* @throws ConstExprEvaluationException if the expression cannot be evaluated
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*/
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public function evaluateDirectly(Expr $expr) {
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return $this->evaluate($expr);
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}
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/** @return mixed */
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private function evaluate(Expr $expr) {
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if ($expr instanceof Scalar\Int_
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|| $expr instanceof Scalar\Float_
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|| $expr instanceof Scalar\String_
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) {
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return $expr->value;
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}
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if ($expr instanceof Expr\Array_) {
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return $this->evaluateArray($expr);
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}
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// Unary operators
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if ($expr instanceof Expr\UnaryPlus) {
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return +$this->evaluate($expr->expr);
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}
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if ($expr instanceof Expr\UnaryMinus) {
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return -$this->evaluate($expr->expr);
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}
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if ($expr instanceof Expr\BooleanNot) {
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return !$this->evaluate($expr->expr);
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}
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if ($expr instanceof Expr\BitwiseNot) {
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return ~$this->evaluate($expr->expr);
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}
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if ($expr instanceof Expr\BinaryOp) {
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return $this->evaluateBinaryOp($expr);
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}
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if ($expr instanceof Expr\Ternary) {
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return $this->evaluateTernary($expr);
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}
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if ($expr instanceof Expr\ArrayDimFetch && null !== $expr->dim) {
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return $this->evaluate($expr->var)[$this->evaluate($expr->dim)];
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}
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if ($expr instanceof Expr\ConstFetch) {
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return $this->evaluateConstFetch($expr);
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}
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return ($this->fallbackEvaluator)($expr);
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}
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private function evaluateArray(Expr\Array_ $expr): array {
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$array = [];
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foreach ($expr->items as $item) {
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if (null !== $item->key) {
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$array[$this->evaluate($item->key)] = $this->evaluate($item->value);
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} elseif ($item->unpack) {
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$array = array_merge($array, $this->evaluate($item->value));
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} else {
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$array[] = $this->evaluate($item->value);
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}
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}
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return $array;
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}
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/** @return mixed */
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private function evaluateTernary(Expr\Ternary $expr) {
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if (null === $expr->if) {
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return $this->evaluate($expr->cond) ?: $this->evaluate($expr->else);
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}
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return $this->evaluate($expr->cond)
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? $this->evaluate($expr->if)
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: $this->evaluate($expr->else);
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}
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/** @return mixed */
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private function evaluateBinaryOp(Expr\BinaryOp $expr) {
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if ($expr instanceof Expr\BinaryOp\Coalesce
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&& $expr->left instanceof Expr\ArrayDimFetch
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) {
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// This needs to be special cased to respect BP_VAR_IS fetch semantics
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return $this->evaluate($expr->left->var)[$this->evaluate($expr->left->dim)]
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?? $this->evaluate($expr->right);
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}
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// The evaluate() calls are repeated in each branch, because some of the operators are
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// short-circuiting and evaluating the RHS in advance may be illegal in that case
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$l = $expr->left;
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$r = $expr->right;
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switch ($expr->getOperatorSigil()) {
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case '&': return $this->evaluate($l) & $this->evaluate($r);
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case '|': return $this->evaluate($l) | $this->evaluate($r);
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case '^': return $this->evaluate($l) ^ $this->evaluate($r);
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case '&&': return $this->evaluate($l) && $this->evaluate($r);
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case '||': return $this->evaluate($l) || $this->evaluate($r);
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case '??': return $this->evaluate($l) ?? $this->evaluate($r);
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case '.': return $this->evaluate($l) . $this->evaluate($r);
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case '/': return $this->evaluate($l) / $this->evaluate($r);
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case '==': return $this->evaluate($l) == $this->evaluate($r);
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case '>': return $this->evaluate($l) > $this->evaluate($r);
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case '>=': return $this->evaluate($l) >= $this->evaluate($r);
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case '===': return $this->evaluate($l) === $this->evaluate($r);
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case 'and': return $this->evaluate($l) and $this->evaluate($r);
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case 'or': return $this->evaluate($l) or $this->evaluate($r);
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case 'xor': return $this->evaluate($l) xor $this->evaluate($r);
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case '-': return $this->evaluate($l) - $this->evaluate($r);
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case '%': return $this->evaluate($l) % $this->evaluate($r);
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case '*': return $this->evaluate($l) * $this->evaluate($r);
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case '!=': return $this->evaluate($l) != $this->evaluate($r);
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case '!==': return $this->evaluate($l) !== $this->evaluate($r);
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case '+': return $this->evaluate($l) + $this->evaluate($r);
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case '**': return $this->evaluate($l) ** $this->evaluate($r);
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case '<<': return $this->evaluate($l) << $this->evaluate($r);
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case '>>': return $this->evaluate($l) >> $this->evaluate($r);
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case '<': return $this->evaluate($l) < $this->evaluate($r);
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case '<=': return $this->evaluate($l) <= $this->evaluate($r);
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case '<=>': return $this->evaluate($l) <=> $this->evaluate($r);
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}
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throw new \Exception('Should not happen');
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}
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/** @return mixed */
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private function evaluateConstFetch(Expr\ConstFetch $expr) {
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$name = $expr->name->toLowerString();
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switch ($name) {
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case 'null': return null;
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case 'false': return false;
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case 'true': return true;
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}
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return ($this->fallbackEvaluator)($expr);
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}
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}
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