Webview frontend becomes unresponsive when LSP mode is active

[rdaum]

First, nice job on the webview front end. Love it.

Today when trying to get LSP to work with Rust I found that LSP mode is enabled (e.g., for Rust via define-language-spec in init.lisp + rust-analyzer), the webview frontend becomes completely unresponsive — no keyboard input, mouse clicks, or tab switching work. The ncurses frontend works fine with the same configuration

I walked through in general and found:

• The editor thread is not blocked, I was able to make a heartbeat timer fires every 2 seconds normally if I add logging
• LSP initialization completes successfully (server starts, initialize/initialized handshake, textDocument/didOpen all succeed)
• Diagnostic notifications arrive and are processed correctly
• The problem is specific to the webview/jsonrpc frontend — ncurses build worked fine

Reproduction, off of 15eb7c4

Add to ~/.lem/init.lisp:

  (lem-lsp-mode/lsp-mode::define-language-spec
      (rust-spec lem-rust-mode:rust-mode)
    :language-id "rust"
    :root-uri-patterns '("Cargo.toml")
    :command '("rust-analyzer")
    :install-command "rustup component add rust-analyzer"
    :readme-url "https://github.com/rust-lang/rust-analyzer"
    :connection-mode :stdio)

Then: ./lem --frontend webview some-rust-file.rs

The editor opens but becomes immediately unresponsive -- e.g. I see tabs but clicking them doesn't change, can't enter minibuffer, document doesn't load. Removing the define-language-spec resolves the issue.

ncurses frontend is as I said not affected.