75 lines
2.7 KiB
Markdown
75 lines
2.7 KiB
Markdown
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Error handling
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==============
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Errors during parsing or analysis are represented using the `PhpParser\Error` exception class. In addition to an error
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message, an error can also store additional information about the location the error occurred at.
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How much location information is available depends on the origin of the error and how many lexer attributes have been
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enabled. At a minimum the start line of the error is usually available.
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Column information
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------------------
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In order to receive information about not only the line, but also the column span an error occurred at, the file
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position attributes in the lexer need to be enabled:
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```php
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$lexer = new PhpParser\Lexer(array(
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'usedAttributes' => array('comments', 'startLine', 'endLine', 'startFilePos', 'endFilePos'),
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));
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$parser = (new PhpParser\ParserFactory)->create(PhpParser\ParserFactory::PREFER_PHP7, $lexer);
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try {
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$stmts = $parser->parse($code);
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// ...
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} catch (PhpParser\Error $e) {
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// ...
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}
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```
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Before using column information its availability needs to be checked with `$e->hasColumnInfo()`, as the precise
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location of an error cannot always be determined. The methods for retrieving column information also have to be passed
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the source code of the parsed file. An example for printing an error:
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```php
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if ($e->hasColumnInfo()) {
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echo $e->getRawMessage() . ' from ' . $e->getStartLine() . ':' . $e->getStartColumn($code)
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. ' to ' . $e->getEndLine() . ':' . $e->getEndColumn($code);
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// or:
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echo $e->getMessageWithColumnInfo();
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} else {
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echo $e->getMessage();
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}
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```
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Both line numbers and column numbers are 1-based. EOF errors will be located at the position one past the end of the
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file.
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Error recovery
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--------------
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The error behavior of the parser (and other components) is controlled by an `ErrorHandler`. Whenever an error is
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encountered, `ErrorHandler::handleError()` is invoked. The default error handling strategy is `ErrorHandler\Throwing`,
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which will immediately throw when an error is encountered.
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To instead collect all encountered errors into an array, while trying to continue parsing the rest of the source code,
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an instance of `ErrorHandler\Collecting` can be passed to the `Parser::parse()` method. A usage example:
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```php
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$parser = (new PhpParser\ParserFactory)->create(PhpParser\ParserFactory::ONLY_PHP7);
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$errorHandler = new PhpParser\ErrorHandler\Collecting;
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$stmts = $parser->parse($code, $errorHandler);
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if ($errorHandler->hasErrors()) {
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foreach ($errorHandler->getErrors() as $error) {
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// $error is an ordinary PhpParser\Error
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}
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}
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if (null !== $stmts) {
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// $stmts is a best-effort partial AST
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}
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```
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The `NameResolver` visitor also accepts an `ErrorHandler` as a constructor argument.
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