Implementation Guide

Performance Guidelines

Message Ordering: Responses to requests should be sent in roughly the same order as the requests appear on the server or client side.

State Management:

Servers should handle partial/incomplete requests gracefully
Use ContentModified error for outdated results
Implement proper cancellation support

Resource Management:

Language servers run in separate processes
Avoid memory leaks in long-running servers
Implement proper cleanup on shutdown

Error Handling

Client Responsibilities:

Restart crashed servers (with exponential backoff)
Handle ContentModified errors gracefully
Validate server responses

Server Responsibilities:

Return appropriate error codes
Handle malformed/outdated requests
Monitor client process health

Transport Considerations

Command Line Arguments:

language-server --stdio                    # Use stdio
language-server --pipe=<n>             # Use named pipe/socket
language-server --socket --port=<port>    # Use TCP socket  
language-server --node-ipc                # Use Node.js IPC
language-server --clientProcessId=<pid>   # Monitor client process

Testing Strategies

Unit Testing:

Mock LSP message exchange
Test individual feature implementations
Validate message serialization/deserialization

Integration Testing:

End-to-end editor integration
Multi-document scenarios
Error condition handling

Performance Testing:

Large file handling
Memory usage patterns
Response time benchmarks

Advanced Topics

Custom Extensions

Experimental Capabilities:

interface ClientCapabilities {
  experimental?: {
    customFeature?: boolean;
    vendorSpecificExtension?: any;
  };
}

Custom Methods:

Use vendor prefixes: mycompany/customFeature
Document custom protocol extensions
Ensure graceful degradation

Security Considerations

Process Isolation:

Language servers run in separate processes
Limit file system access appropriately
Validate all input from untrusted sources

Content Validation:

Sanitize file paths and URIs
Validate document versions
Implement proper input validation

Multi-Language Support

Language Identification:

interface TextDocumentItem {
  uri: DocumentUri;
  languageId: string; // "typescript", "python", etc.
  version: integer;
  text: string;
}

Document Selectors:

type DocumentSelector = DocumentFilter[];

interface DocumentFilter {
  language?: string;    // "typescript"
  scheme?: string;      // "file", "untitled"  
  pattern?: string;     // "**/*.{ts,js}"
}

Symposium