Talks - Chahak Mehta: LSP Demystified - How towrite an LSP server in Python

LSP (Language Server Protocol) provides a standardized way for code editors to communicate with language-specific tooling, introduced by Microsoft in 2016

Language servers communicate via JSON-RPC protocol and handle tasks like:

• Code completion/intellisense
• Error diagnostics/linting
• Hover documentation
• Go to definition
• Code actions and refactoring

The pygls library provides a Python framework for building language servers with minimal boilerplate code

Key benefits:

• One server implementation works with all LSP-compatible editors
• Easier to add new language features (only server-side changes needed)
• Decouples language tooling from editor implementation

Language server workflow:

1. Parse code into abstract syntax tree (AST)
2. Analyze AST for linting/completions/etc
3. Send diagnostics/suggestions back to client

Smart autocompletion is context-aware:

• Suggests based on cursor position in AST
• Can include documentation with suggestions
• Can filter suggestions based on context

Performance considerations:

• Can implement debouncing for keystroke events
• Clients can control when to show suggestions
• Heavy processing only needed after relevant changes

Distribution is straightforward:

• Package as Python library
• Client just needs minimal configuration
• Communication happens over stdio