Language servers

A language server knows your code: it finds errors, jumps to definitions, renames across files and offers completions. imp starts one for you when you open a file it has a server for, if the server is installed. A slow server never holds up your typing.

Servers imp knows

These start by themselves when they're installed:

Language	Server
Rust	`rust-analyzer`
TypeScript and JavaScript	`tsgo`, else `typescript-language-server`, else `tsc --lsp`
Nix	`nil`
Markdown	`marksman`
Python	`pyright`

imp finds the project's root by looking up from the file for a marker such as Cargo.toml or .git. One server runs per project, shared by all its files.

Errors and warnings

The server's diagnostics are underlined in the text, with a sign in the gutter. In normal mode, the message for the cursor's line shows on the status line.

Key	What it does
`]d`	Go to the next diagnostic
`[d`	Go to the previous diagnostic
`SPC c x` or `:diagnostics`	Pick a diagnostic from any file and go to it

While you type, the diagnostics stay as they were. The new ones show when you leave insert mode, so half-typed words don't flash as errors. Until the server sends new ones, the old ones move with the text as you edit.

Finding your way and changing code

Key	What it does
`K`	Show what the server says about the symbol at the cursor
`gd`	Go to its definition
`gr`	Pick one of its references from a menu and go to it
`SPC c r`	Rename it, in every file the server knows of
`SPC c a`	Pick one of the server's code actions, such as a quick fix
`SPC c f`	Format the buffer

There's no signature help and no inlay hints.

Completion

In insert mode, the server's names show in the completion menu at the cursor. The menu opens by itself when you type a letter, or a character the server asks for, often . after a name. You can also open it with C-n, C-p or C-x C-o.

Snippets from the server expand when you accept them. See Completion while typing for the keys in the menu.

Managing servers

Command	What it does
`:lsp-info`	List the running servers
`:lsp-log`	Show what the servers have logged
`:lsp-restart` or `SPC c R`	Restart this buffer's server
`:lsp-stop`	Stop this buffer's server

A server of your own

Set a major mode's server in init.scm. Give the command, the files that mark a project's root, and the language's name:

(define-language-server! 'rust-mode "rust-analyzer" '("Cargo.toml" ".git") "rust")

The command can be a list of commands instead. imp uses the first one that's installed.

Options

Option	Default	What it does
`lsp`	`#t`	Use language servers; `#f` starts none
`lsp-auto-complete`	`#t`	Open the completion menu by itself where a server is running
`lsp-change-delay`	`200`	Milliseconds of quiet before your changes are sent to the server
`lsp-diagnostics-in-insert`	`#f`	Show new diagnostics while you type, not only when you leave insert mode