fix(custom-buffer-file): error when copy-link has no file to copy

cj/copy-link-to-buffer-file did nothing in a non-file buffer, while every sibling copy command signals a user-error. The silent no-op gave no feedback either way. Now it signals a user-error too, and I updated the two tests and the commentary that had documented the silence as intended.

2 files changed, 14 insertions, 10 deletions

diff --git a/modules/custom-buffer-file.el b/modules/custom-buffer-file.el
index d8e97e27..0ca06cf9 100644
--- a/modules/custom-buffer-file.el
+++ b/modules/custom-buffer-file.el
@@ -241,13 +241,16 @@ blast-radius operation on this map.  The VC path is not double-prompted:
           (cj/--delete-buffer-and-file))))))
 
 (defun cj/copy-link-to-buffer-file ()
-  "Copy the full file:// path of the current buffer's source file to the kill ring."
+  "Copy the full file:// path of the current buffer's source file to the kill ring.
+Signal a `user-error' when the buffer is not visiting a file, matching the
+other copy commands in this module."
   (interactive)
   (let ((file-path (buffer-file-name)))
-    (when file-path
-      (setq file-path (concat "file://" file-path))
-      (kill-new file-path)
-      (message "Copied file link to kill ring: %s" file-path))))
+    (unless file-path
+      (user-error "Buffer is not visiting a file"))
+    (setq file-path (concat "file://" file-path))
+    (kill-new file-path)
+    (message "Copied file link to kill ring: %s" file-path)))
 
 (defvar cj/buffer-source-functions
   '((eww-mode         . (lambda () (eww-current-url)))
diff --git a/tests/test-custom-buffer-file-copy-link-to-buffer-file.el b/tests/test-custom-buffer-file-copy-link-to-buffer-file.el
index 262968d6..5ee57b3a 100644
--- a/tests/test-custom-buffer-file-copy-link-to-buffer-file.el
+++ b/tests/test-custom-buffer-file-copy-link-to-buffer-file.el
@@ -4,7 +4,8 @@
 ;; Tests for the cj/copy-link-to-buffer-file function from custom-buffer-file.el
 ;;
 ;; This function copies the full file:// path of the current buffer's file to
-;; the kill ring. For non-file buffers, it does nothing (no error).
+;; the kill ring. For non-file buffers, it signals a user-error, matching its
+;; sibling copy commands.
 
 ;;; Code:
 
@@ -58,12 +59,12 @@
     (test-copy-link-teardown)))
 
 (ert-deftest test-copy-link-non-file-buffer ()
-  "Should do nothing for non-file buffer without error."
+  "Error: a non-file buffer signals `user-error' and leaves the kill ring alone."
   (test-copy-link-setup)
   (unwind-protect
       (with-temp-buffer
         (setq kill-ring nil)
-        (cj/copy-link-to-buffer-file)
+        (should-error (cj/copy-link-to-buffer-file) :type 'user-error)
         (should (null kill-ring)))
     (test-copy-link-teardown)))
 
@@ -195,13 +196,13 @@
     (test-copy-link-teardown)))
 
 (ert-deftest test-copy-link-scratch-buffer ()
-  "Should do nothing for *scratch* buffer."
+  "Error: the *scratch* buffer (no file) signals `user-error'."
   (test-copy-link-setup)
   (unwind-protect
       (progn
         (setq kill-ring nil)
         (with-current-buffer "*scratch*"
-          (cj/copy-link-to-buffer-file)
+          (should-error (cj/copy-link-to-buffer-file) :type 'user-error)
           (should (null kill-ring))))
     (test-copy-link-teardown)))