refactor(dirvish): extract cj/--file-manager-program-for helper

`cj/dirvish-open-file-manager-here' had its platform-dispatch -- xdg-open / open / explorer / shell fallback -- inline as a four-arm cond branching on `executable-find' and `system-type'.  Lift the choice into `cj/--file-manager-program-for', a pure function from (HAS-XDG-OPEN-P SYSTEM-TYPE) to a program-name string or nil.  The wrapper resolves the live values, asks the helper, and either calls the program or falls back to a shell-command.

Six Normal/Boundary tests cover the four return shapes (xdg-open across system types, darwin/windows-nt without xdg-open, the nil fallback for plain Linux without xdg-open and for unknown system-types like Haiku).

2 files changed, 76 insertions, 15 deletions

diff --git a/modules/dirvish-config.el b/modules/dirvish-config.el
index 3fce616e..22d3f07c 100644
--- a/modules/dirvish-config.el
+++ b/modules/dirvish-config.el
@@ -194,6 +194,21 @@ Examples:
 
 ;;; ----------------------- Dirvish Open File Manager Here ----------------------
 
+(defun cj/--file-manager-program-for (has-xdg-open-p system-type)
+  "Return the file-manager command for HAS-XDG-OPEN-P + SYSTEM-TYPE, or nil.
+
+Pure helper used by `cj/dirvish-open-file-manager-here'.  When
+HAS-XDG-OPEN-P is non-nil, returns \"xdg-open\" regardless of
+SYSTEM-TYPE -- xdg-open works on Linux and many ported environments.
+Without xdg-open, falls back to `darwin' -> \"open\", `windows-nt' ->
+\"explorer\", everything else -> nil so the caller can shell-command
+its way out."
+  (cond
+   (has-xdg-open-p "xdg-open")
+   ((eq system-type 'darwin) "open")
+   ((eq system-type 'windows-nt) "explorer")
+   (t nil)))
+
 (defun cj/dirvish-open-file-manager-here ()
   "Open system's default file manager in the current dired/dirvish directory.
 Always opens the file manager in the directory currently being displayed,
@@ -203,22 +218,14 @@ regardless of what file or subdirectory the point is on."
     (if (and current-dir (file-exists-p current-dir))
         (progn
           (message "Opening file manager in %s..." current-dir)
-          ;; Use shell-command with & to run asynchronously and detached
-          (let ((process-connection-type nil)) ; Use pipe instead of pty
-            (cond
-             ;; Linux/Unix with xdg-open
-             ((executable-find "xdg-open")
-              (call-process "xdg-open" nil 0 nil current-dir))
-             ;; macOS
-             ((eq system-type 'darwin)
-              (call-process "open" nil 0 nil current-dir))
-             ;; Windows
-             ((eq system-type 'windows-nt)
-              (call-process "explorer" nil 0 nil current-dir))
-             ;; Fallback to shell-command
-             (t
+          ;; Use pipe instead of pty for the async call-process below.
+          (let* ((process-connection-type nil)
+                 (program (cj/--file-manager-program-for
+                           (executable-find "xdg-open") system-type)))
+            (if program
+                (call-process program nil 0 nil current-dir)
               (shell-command (format "xdg-open %s &"
-                                     (shell-quote-argument current-dir)))))))
+                                     (shell-quote-argument current-dir))))))
       (message "Could not determine current directory."))))
 
 (defun cj/--wallpaper-program-for (env)
diff --git a/tests/test-dirvish-config-file-manager-program.el b/tests/test-dirvish-config-file-manager-program.el
new file mode 100644
index 00000000..bfd4cad9
--- /dev/null
+++ b/tests/test-dirvish-config-file-manager-program.el
@@ -0,0 +1,54 @@
+;;; test-dirvish-config-file-manager-program.el --- Tests for the file-manager dispatch -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; `cj/--file-manager-program-for' is the pure dispatch behind
+;; `cj/dirvish-open-file-manager-here'.  Given whether xdg-open is
+;; present and the running `system-type', it returns the program name
+;; the wrapper should call -- or nil to signal the wrapper should fall
+;; back to a shell-command.  Keeping `executable-find' and `system-type'
+;; outside lets the helper be tested without faking the live machine.
+
+;;; Code:
+
+(require 'ert)
+(require 'package)
+
+(setq package-user-dir (expand-file-name "elpa" user-emacs-directory))
+(package-initialize)
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "elpa/dirvish-2.3.0/extensions"
+                                          user-emacs-directory))
+(require 'user-constants)
+(require 'keybindings)
+(require 'dirvish-config)
+
+(ert-deftest test-cj--file-manager-program-for-xdg-open-on-linux ()
+  "Normal: xdg-open present on Linux returns xdg-open."
+  (should (equal (cj/--file-manager-program-for t 'gnu/linux)
+                 "xdg-open")))
+
+(ert-deftest test-cj--file-manager-program-for-xdg-open-wins-on-macos ()
+  "Boundary: xdg-open present even on macOS returns xdg-open (Linux-isms ported)."
+  (should (equal (cj/--file-manager-program-for t 'darwin)
+                 "xdg-open")))
+
+(ert-deftest test-cj--file-manager-program-for-darwin-no-xdg ()
+  "Normal: macOS without xdg-open returns open."
+  (should (equal (cj/--file-manager-program-for nil 'darwin)
+                 "open")))
+
+(ert-deftest test-cj--file-manager-program-for-windows-no-xdg ()
+  "Normal: Windows without xdg-open returns explorer."
+  (should (equal (cj/--file-manager-program-for nil 'windows-nt)
+                 "explorer")))
+
+(ert-deftest test-cj--file-manager-program-for-linux-without-xdg-falls-back ()
+  "Boundary: Linux without xdg-open returns nil so the wrapper shells out."
+  (should-not (cj/--file-manager-program-for nil 'gnu/linux)))
+
+(ert-deftest test-cj--file-manager-program-for-unknown-system-falls-back ()
+  "Boundary: an unknown `system-type' with no xdg-open returns nil."
+  (should-not (cj/--file-manager-program-for nil 'haiku)))
+
+(provide 'test-dirvish-config-file-manager-program)
+;;; test-dirvish-config-file-manager-program.el ends here