XML Language Server and the VSCode Extension

For my first and ongoing project as an intern at Red Hat, I’ve been working alongside Angelo Zerr and Fred Bricon to develop an implementation of the Language Server Protocol (LSP) for XML. Through the XML language server, developer tools like VSCode and Eclipse receive XML syntax highlighting and checking, code completion, document folding, etc. At the moment we appear to have the most feature rich XML language server implementation, including our Schema-based support which is an essential XML feature that we are most proud of. Combined, all these features make it much easier for developers to work on any type of project involving XML, from the comfort of their favorite editor or IDE.

Watch a demo of the XML VS Code Extension

The XML language server is currently available in VSCode (via Red Hat’s XML extension), Eclipse LSP4E, and soon in Eclipse Che, which should be available in early 2019.

Supported features:

Syntax error reporting

General code completion

Auto-close tags

Automatic node indentation

Symbol highlighting

Document folding

Document links

Document symbols and outline

Renaming support

Document Formatting

DTD validation

XSD validation

XSD based hover

XSD based code completion

XSL support

XML catalogs

File associations

Code actions

Schema Caching

The amount of features will only keep growing, with our second version having recently been released with great improvements, such as local schema caching for faster load times. Some upcoming additions will include major improvements and fixes to DTD and XSD support, which will complement the entire XML suite.

Initiated by Angelo, this language server is a port of Microsoft’s fault-tolerant HTML language server, that we have developed in Java. Since XML is a subset of HTML we were able to build upon the underlying structure of the HTML language server, which in return enabled us to quickly start work on XML specific features.

If you’d like to contribute to the language server, the repository can be found here.

It has been a great experience working on this project with Red Hat and the open source community, especially on a tool that has so much potential. And with the growth of lightweight and cloud based IDE’s like VSCode or Eclipse Che, language servers will be essential to the success of these editors. It’s exciting to know that even as an intern, my work will be a part of a very important movement in the developer space.

I hope you’ll try the XML language server in VSCode, or your favorite editor that supports the language server protocol, and feel free to leave feedback or report any bugs here.

Additional Resources

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