Don't clobber stickiness text properties when printing Eshell prompt

* lisp/eshell/em-prompt.el (eshell--append-text-property): New
function...
(eshell-emit-prompt): ... use it.

* test/lisp/eshell/em-prompt-tests.el
(em-prompt-test/field-properties/merge-stickiness): New test.
(em-prompt-test/field-properties, em-prompt-test/after-failure): Reorder
stickiness values (bug#74230).

1 files changed, 23 insertions, 13 deletions

diff --git a/lisp/eshell/em-prompt.el b/lisp/eshell/em-prompt.el
index de62b5c7d97..37970ac0ba5 100644
--- a/lisp/eshell/em-prompt.el
+++ b/lisp/eshell/em-prompt.el
@@ -119,6 +119,19 @@ arriving, or after."
     (add-hook 'eshell-post-command-hook 'eshell-emit-prompt nil t)
     (eshell-prompt-mode)))
 
+(defun eshell--append-text-property (start end prop value &optional object)
+  "Append to a text property from START to END.
+PROP is the text property to append to, and VALUE is the list of
+property values to append.  OBJECT is the object to propertize, as with
+`put-text-property' (which see)."
+  (let (next)
+    (while (< start end)
+      (setq next (next-single-property-change start prop object end))
+      (put-text-property start next prop
+                         (append (get-text-property start prop object) value)
+                         object)
+      (setq start next))))
+
 (defun eshell-emit-prompt ()
   "Emit a prompt if eshell is being used interactively."
   (when (boundp 'ansi-color-context-region)
@@ -126,19 +139,16 @@ arriving, or after."
   (run-hooks 'eshell-before-prompt-hook)
   (if (not eshell-prompt-function)
       (set-marker eshell-last-output-end (point))
-    (let ((prompt (funcall eshell-prompt-function)))
-      (add-text-properties
-       0 (length prompt)
-       (if eshell-highlight-prompt
-           '( read-only t
-              field prompt
-              font-lock-face eshell-prompt
-              front-sticky (read-only field font-lock-face)
-              rear-nonsticky (read-only field font-lock-face))
-         '( field prompt
-            front-sticky (field)
-            rear-nonsticky (field)))
-       prompt)
+    (let* ((prompt (funcall eshell-prompt-function))
+           (len (length prompt))
+           (sticky-props '(field)))
+      (put-text-property 0 len 'field 'prompt prompt)
+      (when eshell-highlight-prompt
+        (add-text-properties
+         0 len '(read-only t font-lock-face eshell-prompt) prompt)
+        (setq sticky-props `(read-only font-lock-face . ,sticky-props)))
+      (eshell--append-text-property 0 len 'front-sticky sticky-props prompt)
+      (eshell--append-text-property 0 len 'rear-nonsticky sticky-props prompt)
       (eshell-interactive-filter nil prompt)))
   (run-hooks 'eshell-after-prompt-hook))