Protocol extensions for Eglot

Eglot aims to support the Language Server Protocol, but none of its unofficial extensions. Eglot-x adds support for some of these protocol extensions.

If you find a bug in Eglot, please, try to reproduce it without Eglot-x, because Eglot-x substantially modifies Eglot's normal behavior as well.

Add the following lines to your init file to enable eglot-x

    (with-eval-after-load 'eglot
      (require 'eglot-x)
      (eglot-x-setup))

To adjust which extensions are enabled:

    M-x customize-group RET eglot-x RET

Supported extensions

Files extension

This extension allows the client and the server to have separate file systems. For example, the server can run inside a Docker container, or the source code can be on a remote system accessed by Tramp. The client can send files to the server only from the result of project-files. The list of eligible files can further limited by eglot-x-files-visible-regexp and eglot-x-files-hidden-regexp. This feature works if project-roots and project-external-roots are set correctly.

Enabling extension disables Eglot's built-in support for Tramp files.

Additional reference methods

The command `eglot-x-find-refs' is the entry point for the extra methods. You can bind it to a key:

    (define-key eglot-mode-map (kbd "s-.") #'eglot-x-find-refs)

Currently, the ccls and rust-analyzer are the only servers whose extra reference methods eglot-x supports.

Encoding negotiation

The extension allows the client and the server to negotiate a proper encoding to be used in transmitting column positions.

rust-analyzer extensions

experimental extensions

Snippet TextEdits: see variable eglot-x-enable-snippet-text-edit.
Join Lines: see defun eglot-x-join-lines.
Move Item: see defun eglot-x-move-item-down and eglot-x-move-item-up.
On Enter: see defun eglot-x-on-enter.
Matching Brace: see eglot-x-matching-brace. However, emacs' own backward-sexp, and forward-sexp seem to be more useful.
Open External Documentation: see defun eglot-x-open-external-documentation.
Local Documentation: see variable eglot-x-enable-local-docs-support.
Structural Search Replace (SSR): see defun eglot-x-structural-search-replace.

The server checks the correctness of the query while you type:

The replacement process is similar to query-replace:
Workspace Symbols Filtering: see defun eglot-x-find-workspace-symbol.

The xref buffer shows the current matches while the user iteratively types the query and another buffer shows the location of the first match.

Additional input refines the results and the point in main.rs is changed once again to the location of the new first result:

You can change the search scope and kind with C-l and C-M-l, respectively. See variable eglot-x-ws-keymap. The non-default settings are shown between braces:

Currently, the xref buffer shows the first lines of the matches. This is not always helpful.
Runnables: see defun eglot-x-ask-runnables.

Results for the whole buffer:

Selecting the first "runnable":

The "runnable" is executed as a compile-command:
Server Status: see variable eglot-x-enable-server-status. The mode-line displays the status unless it is "permanently OK".
Colored diagnostics: see variable eglot-x-enable-colored-diagnostics.

`flymake-goto-next-error' shows a colored diagnostic message:

(The ansi-color.el of Emacs 27 is too old for this feature, Emacs 29 is OK.)
Open Server Logs: LSP servers can ask the client to show their logs, see variable eglot-x-enable-open-server-logs for details.

rust-analyzer specific extensions

Expand Macro: see defun eglot-x-expand-macro.
Related Tests: see defun eglot-x-ask-related-tests.
Reload Workspace: see defun eglot-x-reload-workspace.
Rebuild proc-macros: see defun eglot-x-rebuild-proc-macros.
Flycheck commands: see defuns eglot-x-run-flycheck, eglot-x-clear-flycheck, and eglot-x-cancel-flycheck. (These commands implement lsp-extensions and have nothing to do with the flycheck Emacs package.)
View Crate Graph: see variable eglot-x-graph-type and defun eglot-x-view-crate-graph.

You can also jump to the crate (Cargo.toml) if the graph-type is not 'svg':

(This command requires graphviz/graph-easy.)
Dependency Tree: see defun eglot-x-find-crate.
View Recursive Memory Layout: the command eglot-x-view-recursive-memory-layout shows the memory layout of the thing under point.

Tooltips show the column names: offset, size, alignement, number of gaps, and gap-size. The output format is inspired by pahole, which (I think) more practical than the upstream graphical output:

The built-in outline-minor-mode helps to naviagate / understand a recursive layout.

A better layout optimization approach relies on run-time statistics as well, which this command does not provide.