78 lines
2.5 KiB
Markdown
78 lines
2.5 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\Parser($lexer);
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try {
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$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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} else {
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echo $e->getMessage();
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}
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```
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Both line numbers and column numbers are 1-based. EOF errors will be located at the position one past the end of the
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file.
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Error recovery
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--------------
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> **EXPERIMENTAL**
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By default the parser will throw an exception upon encountering the first error during parsing. An alternative mode is
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also supported, in which the parser will remember the error, but try to continue parsing the rest of the source code.
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To enable this mode the `throwOnError` parser option needs to be disabled. Any errors that occurred during parsing can
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then be retrieved using `$parser->getErrors()`. The `$parser->parse()` method will either return a partial syntax tree
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or `null` if recovery fails.
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A usage example:
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```php
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$parser = new PhpParser\Parser(new PhpParser\Lexer, array(
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'throwOnError' => false,
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));
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$stmts = $parser->parse($code);
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$errors = $parser->getErrors();
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foreach ($errors as $error) {
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// $error is an ordinary PhpParser\Error
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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 error recovery implementation is experimental -- it currently won't be able to recover from many types of errors.
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