Support xref in emacs

[omajid]

Emacs includes a consistent way to look up (cross reference) identifiers: https://www.gnu.org/software/emacs/manual/html_node/emacs/Xref.html

It would be great if, instead of omnisharp-specific commands like omnisharp-go-to-definition and omnisharp-find-usages, we could delegate to xref and it's standard keybindings across modes.

A simple implementation might be somthing like this:

(add-hook 'xref-backend-functions 'omnisharp--xref-backend)

(defun omnisharp--xref-backend () (when omnisharp-mode 'omnisharp))

(cl-defmethod xref-backend-definitions ((_backend (eql omnisharp)) symbol)
  (omnisharp--xref-find-definitions symbol))

(defun omnisharp---xref-definitions (symbol)
  "Return definitions for symbol."
  ...
  (xref-make ""
             (xref-make-file-location
              (omnisharp--get-filename response)
              (cdr (assoc 'Line json-result))

I tried implementing omnisharp---xref-definitions, but it seems a bit tricky to mix the sync-style behaviour that xref expects from the async style omnisharp generally uses.

[andyleejordan]

For what it's worth, I have bound:

  :bind (:map omnisharp-mode-map
              ([remap xref-find-definitions] . omnisharp-go-to-definition)
              ([remap xref-find-references] . omnisharp-find-usages)
              ;; `xref-pop-marker-stack' works as expected.)

To get xref-like behaviors.