Sideeffect checking `cider--xref-backend`

[ericdallo]

When doom runs (xref-find-backend) to find current xref backend, cider gives a error: No linked CIDER sessions. xref backend functions should not have side-effects like that, this is making doom's code not be able to check for other backends like lsp making users need to jack in repl to use doom's lsp find-definition for example even if not using cider find definition.

Expected behavior

(cider--xref-backend) not throw any side effects like checking if repl is available.

Actual behavior

(cider--xref-backend) checks if repl is available, throwing a error message if not.

Steps to reproduce the problem

M-x (cider--xref-backend) with a repl not enabled in a project.

Environment & Version information

CIDER version information

;; CIDER 1.3.0 (Ukraine), nREPL 0.9.0
;; Clojure 1.11.0, Java 11.0.12

Emacs version

28.0.91

Operating system

NixOS

[vemv]

Looks like the ensure argument is being passed to cider-current-repl when calling this:

cider/cider-find.el

Lines 233 to 238 in 1e27eba

	(defun cider--xref-backend ()
	"Used for xref integration."
	;; Check if `cider-nrepl` middleware is loaded. Allows fallback to other xref
	;; backends, if cider-nrepl is not loaded.
	(when (cider-nrepl-op-supported-p "ns-path")
	'cider))

[ericdallo]

Yes, here exactly:

cider/cider-client.el

Line 166 in 65a23e5

(nrepl-op-supported-p op (or connection (cider-current-repl nil 'ensure))))

[vemv]

PR welcome adding extra arguments and/or wrapped functions here and there, wdyt?

It would be particularly appreciated from that the implicit QAing (I don't use xref for instance, so can't QA this atm)

[ericdallo]

Proposal here @vemv