Language Server

Language Server Protocol implementation for custom elements. See LSP Integration for editor setup and Using LSP Features for usage guidance.

Supported LSP Methods

Text Document Features

• textDocument/hover - Show element and attribute documentation on hover
• textDocument/completion - Provide tag and attribute completion suggestions
• textDocument/definition - Jump to custom element source definitions
• textDocument/diagnostic - Pull-based diagnostics (LSP 3.17); falls back to push via textDocument/publishDiagnostics for older clients
• textDocument/codeAction - Provide one-click autofixes for validation errors
• textDocument/inlayHint - Show attribute type annotations and slot biscuits inline
• textDocument/didOpen - Track when documents are opened in the editor
• textDocument/didChange - Handle incremental document changes
• textDocument/didClose - Clean up resources when documents are closed

Workspace Features

• workspace/symbol - Search and navigate custom elements across the entire workspace
• workspace/diagnostic - Workspace-wide pull diagnostics (LSP 3.17)
• workspace/didChangeConfiguration - Update server settings at runtime

Server Lifecycle

• initialize - Establish server capabilities and workspace configuration
• shutdown - Gracefully terminate the language server
• $/setTrace - Control debug logging verbosity (LSP standard)

Configuration

Settings

The LSP server reads settings from the cem namespace in initializationOptions and workspace/didChangeConfiguration. Settings can be changed at runtime without restarting the server.

VS Code Example

{
  "cem.inlayHints": true
}

Neovim Example

settings = {
  cem = {
    inlayHints = true,
  },
}

Initialization Options

The LSP server accepts custom initialization options for loading additional packages:

{
  "initializationOptions": {
    "additionalPackages": [
      "npm:@rhds/elements@2.0.0",
      "https://cdn.jsdelivr.net/npm/@shortfuse/materialdesignweb/",
      "jsr:@example/elements"
    ],
    "cem": {
      "inlayHints": true
    }
  }
}

VS Code Example

In your VS Code settings.json:

{
  "cem.additionalPackages": [
    "npm:@rhds/elements@2.0.0",
    "https://cdn.jsdelivr.net/npm/@example/components/"
  ]
}

The VS Code extension passes these as initializationOptions.additionalPackages to the LSP server.

Supported Specifiers

Note: URLs must point to the package root (where package.json lives). The server reads the customElements field from package.json to locate the manifest.

Protocol Features

Pull Diagnostics (LSP 3.17)

When the client supports LSP 3.17 pull diagnostics (textDocument/diagnostic), the server uses the pull model instead of push notifications. This reduces server-initiated traffic and enables caching. Clients that do not advertise diagnostic capability automatically fall back to push via textDocument/publishDiagnostics.

Inlay Hints

Inlay hints display inline annotations:

• Attribute types: Shows : Boolean, : String, etc. after attribute values
• Slot biscuits: Shows slot: header after the closing tag of slotted elements

Disable inlay hints by setting cem.inlayHints to false in your editor settings.

Deprecated Elements and Attributes

Elements, attributes, and slots marked as deprecated in the manifest are reported with DiagnosticTag.Deprecated, rendering as strikethrough in supporting editors. If the manifest includes a deprecation reason, it appears in the diagnostic message.