lsp-mode and `embark-prefix-help-command`

[jdtsmith]

Although it works with normal prefix help, the lsp-mode prefix (s-' for me) does not work with embark-prefix-help-command (see emacs-lsp/lsp-mode#3203). I think that's because the bindings are all rewritten to be menu-items, e.g.:

(menu-item "maybe-lsp-ui-peek-find-references" lsp-ui-peek-find-references :filter (lambda (item) (when (with-current-buffer (or (when (buffer-live-p lsp--describe-buffer) lsp--describe-buffer) (current-buffer)) (and (fboundp 'lsp-ui-peek-find-references) (lsp-feature\? "textDocument/references"))) item)))

This is apparently by design:

(defmacro lsp-define-conditional-key (keymap key def desc cond &rest bindings)
  "In KEYMAP, define key sequence KEY as DEF conditionally.
This is like `define-key', except the definition disappears
whenever COND evaluates to nil.
DESC is the short-description for the binding.
BINDINGS is a list of (key def desc cond)."
...

This macro repurposes menu-item bindings as normal bindings so it can disable them using a :filter form. Embark clears these bindings out as "not real key bindings". Which clearly isn't the case here.

Example:

C-h b s-' h h:

s-' h h runs the command lsp-describe-thing-at-point (found in
lsp-mode-map), which is an interactive compiled Lisp function in
‘lsp-mode.el’.

It is bound to s-' h h.

(lsp-describe-thing-at-point)

Display the type signature and documentation of the thing at
point.

with the relevant bit of the keymap:

	  (104 keymap
	       (104 menu-item "maybe-lsp-describe-thing-at-point" lsp-describe-thing-at-point :filter
		    (lambda #1#
		      (when
			  (with-current-buffer #2#
			    (lsp-feature\? "textDocument/hover"))
			. #3#)))

[minad]

See #383

[jdtsmith]

Interesting. Is it relatively easy to first add support for menu-item key bindings?

[oantolin]

I've added preliminary support for menu-items but it just always shows all of them, none of this disappearing stuff is supported yet.

[oantolin]

OK, now :filter is supported. If you're still using lsp, please let me know if da144277663d761a22e0425117528b19b4fd43ba fixes this issue.

[oantolin]

I'm not sure I want to install and configure lsp just to test whether the :filter support in Embark really fixes this issue. I'll optimistically trust that it does, but please reopen the issue if there are still any problems.