Parser Error Handling
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Create new accountRequest new password Navigation recent posts Home » forums » LtU ForumQuestion: Graceful error recovery during parsing I was hoping for a few pointers to good information
Antlr4 Error Handling
on parsers that can recover from errors and continue to parse the antlr error listener example remainder of their input, skipping portions of the text that are not valid in a clean way. Thanks!
Antlr Error Handling
By Nathan Sobo at 2005-10-03 08:10 | LtU Forum | previous forum topic | next forum topic | other blogs | 16462 reads Comment viewing options Flat list - collapsed antlr4 throw exception on error Flat list - expanded Threaded list - collapsed Threaded list - expanded Date - newest first Date - oldest first 10 comments per page 30 comments per page 50 comments per page 70 comments per page 90 comments per page 150 comments per page 200 comments per page Select your preferred way to display the comments and click "Save settings" recognitionexception antlr 4 to activate your changes. JavaCC uses Java try/catch in BNF rules You can have a look at the brief explanation of this feature here. By Arnaud Clere at Mon, 2005-10-03 08:57 | login or register to post comments Here are some tips(from personal experience) If you mean that what you want is to ignore the error input and proceed with the rest, hopefully correct, input, here are some tips from personal experience: continue parsing from the token after then one that caused the error. For example, if token N caused the parser to fail, continue parsing from token N+1. This can be slow, especially if the parsing rules are big. use some tips from the grammar; for example, curly-bracket language compilers use curly brackets and keywords to find out the propable end of error region. If you mean that what you want is to undo the actions done during parsing due to an error found in the later part of the source code, then you have to rethink the way parsing is done: you don't have to do any
fatal error. This version of the Echo program uses the nonvalidating parser. So it can't tell whether the XML document contains
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the right tags or whether those tags are in the right sequence. bailerrorstrategy In other words, it can't tell you whether the document is valid. It can, however, tell whether or
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not the document is well formed. In this section, you'll modify the slide-show file to generate various kinds of errors and see how the parser handles them. You'll also http://lambda-the-ultimate.org/node/1018 find out which error conditions are ignored by default, and you'll see how to handle them. Note: The XML file used in this exercise is slideSampleBad1.xml, as described in Introducing an Error. The output is in Echo05-Bad1.txt. (The browsable versions are slideSampleBad1-xml.html and Echo05-Bad1.html.) When you created slideSampleBad1.xml, you deliberately created an https://docs.oracle.com/cd/E17802_01/j2ee/j2ee/1.4/docs/tutorial-update2/doc/JAXPSAX5.html XML file that was not well formed. Run the Echo program on that file now. The output now gives you an error message that looks like this (after formatting for readability): org.xml.sax.SAXParseException: The element type "item" must be terminated by the matching end-tag "". ... at org.apache.xerces.parsers.AbstractSAXParser... ... at Echo.main(...) Note: The foregoing message was generated by Xerces, the XML parser that is part of the JAXP 1.2 implementation libraries. If you are using a different parser, the error message is likely to be somewhat different. When a fatal error occurs, the parser cannot continue. So if the application does not generate an exception (which you'll see how to do a moment), then the default error-event handler generates one. The stack trace is generated by the Throwable exception handler in your main method: ... } catch (Throwable t) { t.printStackTrace(); } That stack trace is not very useful. Next, you'll see how to generate better diagnostics when an error occurs. Handling a SAXParseException When the error was encountered, the parser generated a SAXParseException--a subclass of SAXException that identifies
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this http://stackoverflow.com/questions/17709936/xml-parser-error-handling site About Us Learn more about Stack Overflow the company Business Learn more https://doc.rust-lang.org/book/error-handling.html about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up XML parser error handling error handling up vote 1 down vote favorite I would very much appreciate your help with this. Basically, I have a PHP webpage, where the user chooses a city name (by its code) and this is then sent to a script, which finds the city in a database, gets an XML file associated with it, which contains its current weather, and then displays it. parser error handling It all works fine except when the user selects a code, which does not exist. What then happens is that I get the message: Warning: SimpleXMLElement::__construct() [simplexmlelement.--construct]: Entity: line 1: parser error : Start tag expected, '<' not found in ... The major problem with that is, that it stops all loading, so not only does the user see this, but also, the rest of the page including HTML and everything is just not loaded. What I would like is to have some sort of a check, that in case the file is not found has a wrong structure, simply echoes some message like "Error, city not found" and skips the rest of the script, but loads the rest of the webpage, its HTML etc. I found some solutions on the internet but I was not able to implement it successfully. The code that loads the actual xml looks like this: public function __construct($query, $units = 'imperial', $lang = 'en', $appid = ''){ $xml = new SimpleXMLElement(OpenWeatherMap::getRawData($query, $units, $lang, $appid, 'xml')); $this->city = new _City($xml->city['id'], $xml->city['name'], $xml->city->coord['lon'], $xml->city->coord['lat'], $xml->city->country); etc. In case the city is not found, instead of
Borrowing 4.10. Lifetimes 4.11. Mutability 4.12. Structs 4.13. Enums 4.14. Match 4.15. Patterns 4.16. Method Syntax 4.17. Strings 4.18. Generics 4.19. Traits 4.20. Drop 4.21. if let 4.22. Trait Objects 4.23. Closures 4.24. Universal Function Call Syntax 4.25. Crates and Modules 4.26. `const` and `static` 4.27. Attributes 4.28. `type` aliases 4.29. Casting between types 4.30. Associated Types 4.31. Unsized Types 4.32. Operators and Overloading 4.33. Deref coercions 4.34. Macros 4.35. Raw Pointers 4.36. `unsafe` 5. Effective Rust 5.1. The Stack and the Heap 5.2. Testing 5.3. Conditional Compilation 5.4. Documentation 5.5. Iterators 5.6. Concurrency 5.7. Error Handling 5.8. Choosing your Guarantees 5.9. FFI 5.10. Borrow and AsRef 5.11. Release Channels 5.12. Using Rust without the standard library 6. Nightly Rust 6.1. Compiler Plugins 6.2. Inline Assembly 6.3. No stdlib 6.4. Intrinsics 6.5. Lang items 6.6. Advanced linking 6.7. Benchmark Tests 6.8. Box Syntax and Patterns 6.9. Slice Patterns 6.10. Associated Constants 6.11. Custom Allocators 7. Glossary 8. Syntax Index 9. Bibliography Error Handling Like most programming languages, Rust encourages the programmer to handle errors in a particular way. Generally speaking, error handling is divided into two broad categories: exceptions and return values. Rust opts for return values. In this section, we intend to provide a comprehensive treatment of how to deal with errors in Rust. More than that, we will attempt to introduce error handling one piece at a time so that you'll come away with a solid working knowledge of how everything fits together. When done naïvely, error handling in Rust can be verbose and annoying. This section will explore those stumbling blocks and demonstrate how to use the standard library to make error handling concise and ergonomic. Table of Contents This section is very long, mostly because we start at the very beginning with sum types and combinators, and try to motivate the way Rust does error handling incrementally. As such, programmers with experience in other expressive type systems may want to jump around. The Basics Unwrapping explained The Option type Composing Option