LSP Features

Pre-Release

Verter is pre-release software. APIs may change between releases — see the API Stability document.

Verter includes a full Rust LSP server (verter-lsp) that communicates with editors over stdio. The server is launched automatically by the VS Code extension and implements a comprehensive set of Language Server Protocol features.

Text Document Features

Feature	LSP Method	Description
Completion	textDocument/completion	Context-aware completions with trigger characters . @ < : " ' and space. Supports resolve for additional detail.
Hover	textDocument/hover	Type information, CSS rules on template elements, matched elements on CSS selectors
Definition	textDocument/definition	Go-to-definition for bindings, imports, CSS-to-template navigation, DOM query selectors
Type Definition	textDocument/typeDefinition	Navigate to type declarations
Declaration	textDocument/declaration	Navigate to declarations
References	textDocument/references	Find all references to a symbol
Rename	textDocument/rename	Symbol renaming with prepare support (textDocument/prepareRename) for validation before rename
Diagnostics	textDocument/diagnostic	Pull-based diagnostics with inter-file dependency support. Covers script errors, template errors, and Vue-specific lint rules.
Document Symbols	textDocument/documentSymbol	Document outline showing the structure of SFC blocks, script declarations, and template elements
Document Highlight	textDocument/documentHighlight	Highlight all occurrences of the same symbol in the current document
Signature Help	textDocument/signatureHelp	Function signature information with trigger characters ( and ,, retrigger on ,

Navigation

Feature	LSP Method	Description
Folding Range	textDocument/foldingRange	Folding ranges for SFC blocks (<template>, <script>, <style>) and nested template elements
Selection Range	textDocument/selectionRange	Smart selection expansion -- progressively selects larger syntactic units
Linked Editing	textDocument/linkedEditingRange	Rename matching open/close HTML tags simultaneously
Call Hierarchy	textDocument/prepareCallHierarchy	Call hierarchy navigation for incoming and outgoing calls
Document Link	textDocument/documentLink	Clickable links in source code (e.g., import paths, src attributes)

Code Intelligence

Feature	LSP Method	Description
Code Actions	textDocument/codeAction	Quick fixes, refactoring, organize imports (source.organizeImports), and extract component (refactor.extract). Supported kinds: source.organizeImports, quickfix, refactor, refactor.extract.
Code Lens	textDocument/codeLens	Code lens annotations displayed above code elements
Inlay Hints	textDocument/inlayHint	Inline hints showing DOM query matched elements and useTemplateRef matched refs
Semantic Tokens	textDocument/semanticTokens/full	Full semantic token support with 23 token types and 10 modifiers

Semantic Token Types

The server provides the following 23 semantic token types:

namespace, type, class, enum, interface, struct, typeParameter, parameter, variable, property, enumMember, event, function, method, macro, keyword, modifier, comment, string, number, regexp, operator, decorator

Semantic Token Modifiers

The following 10 modifiers can be applied to any token type:

declaration, definition, readonly, static, deprecated, abstract, async, modification, documentation, defaultLibrary

Formatting and Color

Feature	LSP Method	Description
Document Formatting	textDocument/formatting	Format the entire document
Color Information	textDocument/documentColor	CSS color picker with color presentation support

Workspace Features

Feature	LSP Method	Description
Workspace Symbols	workspace/symbol	Project-wide symbol search across all .vue files
Workspace Folders	workspace/workspaceFolders	Multi-root workspace support with change notifications
File Operations	workspace/didCreateFiles, workspace/didDeleteFiles	Tracks file creation and deletion for cache invalidation

Document Synchronization

The server uses incremental text document synchronization (TextDocumentSyncKind.Incremental), meaning only the changed portions of a document are sent from the client on each edit. This minimizes communication overhead for large files.

Position Encoding

The LSP server negotiates position encoding with the client during the initialize handshake. The preferred order is:

1. UTF-8 (preferred -- no conversion needed since Rust strings are UTF-8)
2. UTF-32
3. UTF-16 (fallback -- standard LSP default)

The negotiated encoding is announced in ServerCapabilities.position_encoding and applies to all positions in both standard and custom protocol messages.

Architecture

The LSP binary is structured as follows:

main.rs               -- stdio transport, CLI argument parsing
server.rs              -- LSP message loop, request dispatch
documents/             -- Document tracking and incremental sync
features/              -- Individual LSP feature handlers
analysis/              -- Static analysis integration
css/                   -- CSS-specific language features
tsgo/                  -- TSGO type provider (LSP over stdio, resilient wrapper)
tsserver/              -- tsserver type provider (newline-delimited JSON, resilient wrapper)
sync_coordinator.rs    -- Background file sync with debounce (freeze prevention)
config.rs              -- Lint configuration discovery (.verterrc.json, ESLint, VS Code)
capabilities.rs        -- Server capability registration

Each feature module in features/ handles one or more related LSP methods. The server dispatches incoming requests to the appropriate feature handler based on the LSP method.

Type Provider

The LSP delegates TypeScript type checking to an external process. Two backends are supported:

Backend	Binary	Protocol	Use Case
TSGO	tsgo (Go binary)	LSP over stdio	Fast, native TS checking (preview)
tsserver	node tsserver.js	Newline-delimited JSON	Workspace TS version, plugin support

Provider selection is configured via the --type-provider CLI arg or verter.typeProvider VS Code setting. See Settings Reference for details.

TSGO Limitation

TSGO has a known limitation: re-exported .vue components (e.g., barrel files) may lose their typing. This is why auto mode defaults to tsserver when a workspace TypeScript installation is found.