minimal_lsp.rs example doubly-nests the InitializeResult capabilities property

rust-analyzer version: rust-analyzer version: 0.3.2743-standalone (6a1246b69c 2026-01-04) [c:\Users\Grego.vscode\extensions\rust-lang.rust-analyzer-0.3.2743-win32-x64\server\rust-analyzer.exe]

rustc version: rustc 1.92.0 (ded5c06cf 2025-12-08)

editor or extension: VSCode 1.107.1 994fd12f8d3a5aa16f17d42c041e5809167e845a x64 rust-lang.rust-analyzer 0.3.2743

relevant settings: N/A

The minimal_lsp.rs lsp-server example does not return a valid InitializeResult; it doubly-nests the capabilities property by specifying it in two places:

minimal_lsp.rs line 132:

  let init_value = serde_json::json!({
      "capabilities": caps,
      "offsetEncoding": ["utf-8"],
  });

  let init_params = connection.initialize(init_value)?;

connection.initialize definition in lib.rs line 287:

let initialize_data = serde_json::json!({
    "capabilities": server_capabilities,
});

self.initialize_finish(id, initialize_data)?;

For background, I'm using this library to learn about and implement my own language server and this error was tough to debug as a novice. Updating the example may help other interested folks like myself build the skills to help contribute back to this amazing open-source project.

Thank you for all your work on this awesome VSCode extension and supporting libraries!

Start with lib/lsp-server/examples/minimal_lsp.rs around line 132 and compare its initialization data with connection.initialize in lib/lsp-server/src/lib.rs around line 287. Check the LSP InitializeResult specification and run the example's relevant build or tests. Done means the example produces a correctly shaped InitializeResult without doubly nesting capabilities.