Add cider-jump-to-always-use-same-window

Provide a means to control what window to use when jumping to a definition with
`cider-jump-to`.

By default, always use current window.

Provide an option to use existing buffer in current frame when there is one that
is showing the target buffer. (This is the old behaviour, but note that it does
not work well with `cider-pop-back` (M-,).

This fixes #2499

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### New features
 
+* [#2757](https://github.com/clojure-emacs/cider/pull/2757): Add `cider-jump-to-always-use-same-window`
 * [#2738](https://github.com/clojure-emacs/cider/pull/2738): Add ability to lookup a function symbol when cursor is at the opening paren.
 * [#2735](https://github.com/clojure-emacs/cider/pull/2735): New debugger command `P` to inspect an arbitrary expression, it was previously bound to `p` which now inspects the current value.
 * [#2729](https://github.com/clojure-emacs/cider/pull/2729): New cider inspector command `cider-inspector-def-current-val` lets you define a var with the current inspector value.

cider-common.el

@@ -127,6 +127,14 @@ On failure, read a symbol name using PROMPT and call CALLBACK with that."
 
 (declare-function cider-mode "cider-mode")
 
+(defcustom cider-jump-to-always-use-same-window t
+  "Determines what window `cider-jump-to` uses.
+If non-nil, always use current window.
+If nil: if target buffer is being displayed in the current frame use its
+window, otherwise use the current window."
+  :type 'boolean
+  :group 'cider)
+
 (defun cider-jump-to (buffer &optional pos other-window)
   "Push current point onto marker ring, and jump to BUFFER and POS.
 POS can be either a number, a cons, or a symbol.
@@ -139,8 +147,10 @@ If OTHER-WINDOW is non-nil don't reuse current window."
     (ring-insert find-tag-marker-ring (point-marker)))
   (if other-window
       (pop-to-buffer buffer 'display-buffer-pop-up-window)
-    ;; like switch-to-buffer, but reuse existing window if BUFFER is visible
-    (pop-to-buffer buffer '((display-buffer-reuse-window display-buffer-same-window))))
+    (pop-to-buffer buffer (if cider-jump-to-always-use-same-window
+                              '((display-buffer-same-window))
+                            '((display-buffer-reuse-window
+                               display-buffer-same-window)))))
   (with-current-buffer buffer
     (widen)
     (goto-char (point-min))

doc/modules/ROOT/pages/repl/configuration.adoc

@@ -261,3 +261,15 @@ can set:
 ----
 (setq cider-repl-require-ns-on-set t)
 ----
+
+== Control what window to use when jumping to a definition
+
+By default M-. and other commands that jump to a definition use the current
+window to show the definition. An alternative is to use an existing buffer in
+the current frame when there is one that is showing the target buffer. If you
+want this alternative behaviour, set:
+
+[source,lisp]
+----
+(setq cider-jump-to-always-use-same-window nil)
+----