feat(window): kill the other window's buffer with C-; b K

`cj/kill-other-window-buffer' (in undead-buffers.el, on `C-; b K') kills or buries the buffer shown in the other window and leaves that window and the split alone. The window just shows whatever bury/kill surfaces next. It reuses `cj/kill-buffer-or-bury-alive', so buffers in `cj/undead-buffer-list' (like `*scratch*') get buried. With more than two windows it acts on `next-window'. Sibling of `cj/kill-other-window' (M-S-o), which deletes the other window. This one keeps it.

3 files changed, 96 insertions, 1 deletions

diff --git a/modules/custom-buffer-file.el b/modules/custom-buffer-file.el
index f4401d1f..ef4fc945 100644
--- a/modules/custom-buffer-file.el
+++ b/modules/custom-buffer-file.el
@@ -17,6 +17,8 @@
 ;;
 ;; Keybindings under ~C-; b~:
 ;; - ~C-; b k~ kill buffer and window (delete window, kill/bury buffer)
+;; - ~C-; b K~ kill the other window's buffer, keeping that window/split
+;;   (cj/kill-other-window-buffer in undead-buffers.el)
 ;; - ~C-; b <arrow>~ move the active window's divider that way (via windsize);
 ;;   bare arrows keep nudging until any other key (cj/window-resize-sticky in
 ;;   ui-navigation.el)
@@ -37,8 +39,9 @@
 (require 'mm-decode)
 (require 'external-open) ;; for cj/xdg-open, cj/open-this-file-with
 
-;; cj/kill-buffer-and-window defined in undead-buffers.el
+;; cj/kill-buffer-and-window and cj/kill-other-window-buffer defined in undead-buffers.el
 (declare-function cj/kill-buffer-and-window "undead-buffers")
+(declare-function cj/kill-other-window-buffer "undead-buffers")
 
 ;; cj/window-resize-sticky (C-; b <arrow>) defined in ui-navigation.el
 (declare-function cj/window-resize-sticky "ui-navigation")
@@ -449,6 +452,7 @@ Signals an error if:
   "n" #'cj/copy-buffer-name
   "l" #'cj/copy-link-to-buffer-file
   "k" #'cj/kill-buffer-and-window
+  "K" #'cj/kill-other-window-buffer
   "P" #'cj/print-buffer-ps
   "t" #'cj/clear-to-top-of-buffer
   "b" #'cj/clear-to-bottom-of-buffer
@@ -486,6 +490,7 @@ Signals an error if:
     "C-; b n" "copy buffer name"
     "C-; b l" "copy file link"
     "C-; b k" "kill buffer and window"
+    "C-; b K" "kill other window's buffer"
     "C-; b P" "print to PS"
     "C-; b t" "clear to top"
     "C-; b b" "clear to bottom"
diff --git a/modules/undead-buffers.el b/modules/undead-buffers.el
index f79afb4b..c85bde94 100644
--- a/modules/undead-buffers.el
+++ b/modules/undead-buffers.el
@@ -8,6 +8,8 @@
 ;;
 ;; Additional helper commands and key bindings:
 ;;  - C-; b k (=cj/kill-buffer-and-window=): delete this window and bury/kill its buffer.
+;;  - C-; b K (=cj/kill-other-window-buffer=): bury/kill the other window's buffer,
+;;    keeping that window and the split intact.
 ;;  - M-O (=cj/kill-other-window=): delete the next window and bury/kill its buffer.
 ;;  - M-M (=cj/kill-all-other-buffers-and-windows=): kill or bury all buffers except
 ;;    the current one and delete all other windows.
@@ -77,6 +79,20 @@ ARG is passed to `save-some-buffers'."
 	(cj/kill-buffer-or-bury-alive buf)))
 (keymap-global-set "M-S-o" #'cj/kill-other-window)
 
+(defun cj/kill-other-window-buffer ()
+  "Kill or bury the buffer shown in the other window, keeping that window
+and the split intact -- the window then shows whatever bury/kill surfaces
+next.  With more than two windows, acts on `next-window'.
+
+Sibling of `cj/kill-other-window', which deletes the other window; here the
+split is preserved.  Buffers in `cj/undead-buffer-list' are buried."
+  (interactive)
+  (if (one-window-p)
+	  (user-error "No other window")
+	(with-selected-window (next-window)
+	  (cj/kill-buffer-or-bury-alive (current-buffer)))))
+;; Keybinding in custom-buffer-file.el (C-; b K)
+
 (defun cj/kill-all-other-buffers-and-windows ()
   "Kill or bury all other buffers, then delete other windows."
   (interactive)
diff --git a/tests/test-undead-buffers--kill-other-window-buffer.el b/tests/test-undead-buffers--kill-other-window-buffer.el
new file mode 100644
index 00000000..4dbbb710
--- /dev/null
+++ b/tests/test-undead-buffers--kill-other-window-buffer.el
@@ -0,0 +1,74 @@
+;;; test-undead-buffers--kill-other-window-buffer.el --- Tests for cj/kill-other-window-buffer -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; `cj/kill-other-window-buffer' kills (or buries, for `cj/undead-buffer-list'
+;; buffers) the buffer shown in the other window, leaving that window and the
+;; split intact -- the window then shows whatever bury/kill surfaces next.
+;; Sibling of `cj/kill-other-window' (which deletes the other window); the
+;; distinguishing trait here is that the split is preserved.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
+(require 'undead-buffers)
+
+(ert-deftest test-undead-buffers-kill-other-window-buffer-keeps-the-window ()
+  "Normal: kills the other window's (non-undead) buffer but keeps the window
+and the split -- the current window is left untouched."
+  (let ((other (generate-new-buffer "test-kill-other-window-buffer"))
+        (orig (copy-sequence cj/undead-buffer-list)))
+    (unwind-protect
+        (save-window-excursion
+          (delete-other-windows)
+          (split-window-right)
+          (let* ((win-a (selected-window))
+                 (buf-a (window-buffer win-a))
+                 (win-b (next-window win-a)))
+            (set-window-buffer win-b other)
+            (select-window win-a)
+            (cj/kill-other-window-buffer)
+            (should (window-live-p win-b))
+            (should-not (buffer-live-p other))
+            (should (eq (window-buffer win-a) buf-a))))
+      (setq cj/undead-buffer-list orig)
+      (when (buffer-live-p other) (kill-buffer other)))))
+
+(ert-deftest test-undead-buffers-kill-other-window-buffer-buries-undead ()
+  "Boundary: an undead buffer in the other window is buried, not killed --
+still alive, no longer shown there; the window stays."
+  (let ((other (generate-new-buffer "test-kill-other-undead"))
+        (orig (copy-sequence cj/undead-buffer-list)))
+    (unwind-protect
+        (save-window-excursion
+          (add-to-list 'cj/undead-buffer-list (buffer-name other))
+          (delete-other-windows)
+          (split-window-right)
+          (let* ((win-a (selected-window))
+                 (win-b (next-window win-a)))
+            (set-window-buffer win-b other)
+            (select-window win-a)
+            (cj/kill-other-window-buffer)
+            (should (window-live-p win-b))
+            (should (buffer-live-p other))
+            (should-not (eq (window-buffer win-b) other))))
+      (setq cj/undead-buffer-list orig)
+      (when (buffer-live-p other) (kill-buffer other)))))
+
+(ert-deftest test-undead-buffers-kill-other-window-buffer-errors-with-one-window ()
+  "Error: with only one window there is no other window to act on."
+  (save-window-excursion
+    (delete-other-windows)
+    (should-error (cj/kill-other-window-buffer) :type 'user-error)))
+
+(ert-deftest test-undead-buffers-kill-other-window-buffer-bound-under-c-semicolon-b ()
+  "Normal: reachable via C-; b K."
+  (require 'custom-buffer-file)
+  (should (eq (keymap-lookup cj/buffer-and-file-map "K")
+              #'cj/kill-other-window-buffer)))
+
+(provide 'test-undead-buffers--kill-other-window-buffer)
+;;; test-undead-buffers--kill-other-window-buffer.el ends here