[Feature request] Make eglot works with speedbar

[BooAA]

Speedbar can use imenu to get definitions in a file and display them as tags. (if the return value of imenu-create-index-function is of the from (INDEX-NAME POSITION), speedbar can handle this for free) However, when I tried using speedbar with eglot, speedbar complained "speedbar-insert-generic-list: malformed list!" since it didn't know how to insert the result of eglot-imenu as tags.

It might be useful to make eglot work with speedbar so that we will have tree-like structure to show major definitions for each file.

[arbv]

That would be a good addition. Speedbar is very handy when working with files with a lot of definitions.

[joaotavora]

Or maybe speedbar can understand the correct format of imenu. Eglot is doing nothing more than follow the established format:

imenu--index-alist is a variable defined in `imenu.el'.
Its value is nil

  Automatically becomes buffer-local when set.
  This variable may be risky if used as a file-local variable.

Documentation:
The buffer index alist computed for this buffer in Imenu.

Simple elements in the alist look like (INDEX-NAME . POSITION).
POSITION is the buffer position of the item; to go to the item
is simply to move point to that position.

POSITION is passed to `imenu-default-goto-function', so it can be
a non-number if that variable has been changed (e.g. Semantic
uses overlays for POSITIONs).

Special elements look like
(INDEX-NAME POSITION FUNCTION ARGUMENTS...).
To "go to" a special element means applying FUNCTION to
INDEX-NAME, POSITION, and the ARGUMENTS.

A nested sub-alist element looks like (INDEX-NAME . SUB-ALIST).
The function `imenu--subalist-p' tests an element and returns t
if it is a sub-alist.

There is one simple element with negative POSITION; selecting that
element recalculates the buffer's index alist.

[joaotavora]

A now-deleted I received this morning by one "Tom F" stated the following:

"sb-imenu as described in https://stackoverflow.com/a/36893492 can do this. I'm using eglot with it."

[BooAA]

"sb-imenu as described in https://stackoverflow.com/a/36893492 can do this. I'm using eglot with it."

After (require 'sb-imenu) and (setq speedbar-initial-expansion-list-name "sb-imenu") according to the comment in that stackoverflow question, I got speedbar display imenu index correctly

But when I click or press return on the item, it reports error:

funcall-interactively: Wrong number of arguments: (lambda (text node indent) "Goto the current tag." (interactive) (condition-case nil (progn (speedbar-select-attached-frame) (raise-frame) (select-frame-set-input-focus (selected-frame))) (error nil)) (switch-to-buffer sb-imenu-active-buffer) (goto-char node)), 0

[joaotavora]

That probably explains why the poster deleted the comment. Get someone with Elisp skills to fix speedbar-imenu. Maybe talk to its author. It shouldn't be hard, but unfortunately, I have no time for this.

I do know that M-x imenu works.That's the thing that exists in Emacs, and that's what I'm coding for. Other extensions must also code for Emacs, then they will work with Eglot.

[BooAA]

@joaotavora Below is my attempt to make eglot-imenu work with speedbar by transform the complex alist form to the simple form.

;; borrow from eglot-imenu
(defun eglot-imenu-get-point (one-obj-array)
  (car (eglot--range-region
        (eglot--dcase (aref one-obj-array 0)
          (((SymbolInformation) location)
           (plist-get location :range))
          (((DocumentSymbol) selectionRange)
           selectionRange)))))

(defun eglot-imenu-to-simple-form (menu)
  (cl-loop for form in menu
           collect (cons (car form)
                         (if (imenu--subalist-p form)
                             (eglot-imenu-to-simple-form (cdr form))
                           (eglot-imenu-get-point (cadr form))))))

(advice-add #'eglot-imenu :filter-return #'eglot-imenu-to-simple-form)

;; optional, prevent speedbar from creating additional tags for long entries
(setq speedbar-tag-regroup-maximum-length 100)

Testing on linux kernel with clangd, looks ok to me:

I've made a bug report to ask support for complex imenu form in speedbar, see https://lists.gnu.org/archive/html/bug-gnu-emacs/2021-06/msg01058.html.