Schema-Aware XML

JVM-free XML language support for Visual Studio Code, with schema-aware validation and completion.

Overview

Schema-Aware XML gives VS Code the editing features you expect for XML, and it knows about your schemas. Open a pom.xml, a web.xml or any file that points at an XSD, and completion, hover and validation follow the schema.

Preview release. This is an early 0.1.0 version. Expect rough edges and missing settings; please report problems.

Why this extension

• No Java or JVM. Most XML language servers run on Java. This one is written in TypeScript, so there is no runtime to install or configure.
• Real XSD validation. Schemas are checked by Apache Xerces-C++ compiled to WebAssembly and bundled inside the extension.
• Works on half-typed XML. The parser is fault-tolerant, so completion and the outline keep working while you type.
• Lightweight. The extension activates only when you open an XML document.

Features

• Syntax checking that reports mismatched tags and undefined entities as you type.
• Schema-aware editing for pom.xml, web.xml, persistence.xml and Spring bean files, using built-in XSDs.
• Local schemas: a document that declares xsi:noNamespaceSchemaLocation or xsi:schemaLocation pointing at a local .xsd is validated against it.
• Editor features: completion, hover, outline, folding, formatting, rename, go to definition and find references.
• Workspace aware: watches **/*.xml so the server stays up to date as files change.

Supported files

Requirements

• Visual Studio Code 1.85.0 or newer.
• Nothing else. The language server ships inside the extension.

Known limitations (0.1.0)

• There are no extension settings yet, so custom schema associations cannot be configured from VS Code.
• Only documents saved as files are supported; untitled editors are not.
• The extension runs in desktop VS Code. It does not run in VS Code for the Web yet.

Roadmap

• Extension settings, including custom schema associations.
• Support for untitled documents.
• VS Code for the Web support.

Troubleshooting

Links

• Report an issue
• Language server
• Language service

For contributors

How it works

┌──────────────┐   LSP over stdio   ┌───────────────────────┐
│   VS Code    │ ◀────────────────▶ │  XML language server  │
│  (this ext.) │                    │      (server.js)      │
└──────────────┘                    └───────────────────────┘

This extension is a thin client. It starts the server, keeps it in sync with your workspace and wires it into VS Code; the editing features come from the server.

When an XML file is opened, the extension looks for the server in this order:

1. server/server.js bundled inside the extension (packaged builds).
2. ../xml-language-server/dist/server.js next to this repository (development checkouts).

Development setup

The server depends on the service by relative path, so clone all three side by side:

mkdir xml-workspace
cd xml-workspace

git clone https://github.com/harshanacz/xml-language-service.git
git clone https://github.com/harshanacz/xml-language-server.git
git clone https://github.com/harshanacz/xml-language-client.git

cd xml-language-service
npm install
npm run build

cd ../xml-language-server
npm install
npm run bundle

cd ../xml-language-client
npm install
npm run build

Then open xml-language-client in VS Code, run the Launch Extension debug configuration (or press F5), and open an XML file in the Extension Development Host.

If the server cannot be found, make sure server/server.js exists, or that ../xml-language-server/dist/server.js is built.

Useful scripts

License

MIT