XML Language Server

xml-language-server

LSP (Language Server Protocol) wrapper around xml-language-service. Connects any LSP-compatible editor (VS Code, Neovim, etc.) to the XML language features.

Architecture

VS Code / Editor  ──JSON-RPC over stdio──►  xml-language-server  ──in-process──►  xml-language-service
                  ◄──diagnostics push──                                            └─ Xerces WASM (XSD)

File structure

src/
├── server.ts             — entry point; LSP lifecycle (initialize, config, shutdown) + bootstrap
├── requestHandlers.ts    — registers all LSP request handlers (completion, hover, symbols, etc.)
├── diagnosticsHandler.ts — XSD schema loading, validation via Xerces WASM, pushes diagnostics to client
├── configuration.ts      — schema association config (SchemaConfig, applySchemaSettings)
└── utils.ts              — string helpers + LSP ↔ xml-language-service type adapters

How it works

1. The editor spawns the server process and communicates over stdio using standard JSON-RPC (LSP).
2. On initialize, the server reads schema associations from initializationOptions and registers them.
3. On onInitialized, it fetches xmlLanguageServer.schemas from the editor workspace config and applies them.
4. Every time a document changes, DiagnosticsHandler resolves the matching XSD schema (by filename or namespace), loads all xs:include/xs:import references from disk, and pushes validation diagnostics back to the editor.
5. All other requests (completion, hover, rename, etc.) parse the document on demand and delegate directly to xml-language-service.

Configuration

In your editor's workspace settings, map file patterns to local XSD schemas:

"xmlLanguageServer.schemas": [
  { "pattern": "**/*.synapse.xml", "xsdPath": "schemas/synapse.xsd" },
  { "pattern": "**/proxy-*.xml",   "xsdPath": "schemas/proxy.xsd" }
]

xsdPath can be absolute or relative to the workspace root. The server automatically follows xs:include/xs:import chains in the XSD (up to 10 levels deep, 200 files, 20 MB total).

LSP capabilities

Feature	Trigger
Completion	<, space, ", /
Hover	cursor over element / attribute
Document symbols	outline panel
Folding ranges	editor fold gutter
Rename	rename an XML tag (open + close updated together)
Go to definition	navigate to matching tag
Find references	find all usages of a tag
Formatting	format document command
Diagnostics	pushed on every document change

Related

• xml-language-service — core library
• xml-language-server — this package