Correctly reindent previous line in electric-indent-mode

Fixes: bug#35254

Do this even when electric-indent-inhibit is t, except when the
newline insertion is being performed by electric-layout-mode.

* lisp/electric.el (electric-indent-post-self-insert-function):
Reindent previous line unless operating under
electric-layout-mode.
(electric-layout-post-self-insert-function-1): Bind
electric-indent-inhibit to 'electric-layout-mode.

* test/lisp/electric-tests.el
(electric-layout-control-reindentation): New test.

2 files changed, 27 insertions, 5 deletions

diff --git a/lisp/electric.el b/lisp/electric.el
index 53e53bd975c..a14deb71afb 100644
--- a/lisp/electric.el
+++ b/lisp/electric.el
@@ -270,10 +270,13 @@ or comment."
                   (goto-char before)
                   (condition-case-unless-debug ()
                       (indent-according-to-mode)
-                    (error (throw 'indent-error nil)))
-                  ;; The goal here will be to remove the trailing
-                  ;; whitespace after reindentation of the previous line
-                  ;; because that may have (re)introduced it.
+                    (error (throw 'indent-error nil))))
+                (unless (eq electric-indent-inhibit 'electric-layout-mode)
+                  ;; Unless we're operating under
+                  ;; `electric-layout-mode' (Bug#35254), the goal here
+                  ;; will be to remove the trailing whitespace after
+                  ;; reindentation of the previous line because that
+                  ;; may have (re)introduced it.
                   (goto-char before)
                   ;; We were at EOL in marker `before' before the call
                   ;; to `indent-according-to-mode' but after we may
@@ -451,7 +454,7 @@ If multiple rules match, only first one is executed.")
                       ;; really wants to reindent, then
                       ;; `last-command-event' should be in
                       ;; `electric-indent-chars'.
-                      (let ((electric-indent-inhibit t))
+                      (let ((electric-indent-inhibit 'electric-layout-mode))
                         (funcall nl-after)))))))
             (pcase sym
               ('before (funcall nl-before))
diff --git a/test/lisp/electric-tests.el b/test/lisp/electric-tests.el
index 4f1e5729be1..86c9eff9cda 100644
--- a/test/lisp/electric-tests.el
+++ b/test/lisp/electric-tests.el
@@ -876,6 +876,25 @@ baz\"\""
       (call-interactively (key-binding `[,last-command-event])))
     (should (equal (buffer-string) "int main () {\n  \n}"))))
 
+(ert-deftest electric-layout-control-reindentation ()
+  "Same as `e-l-int-main-kernel-style', but checking Bug#35254."
+  (ert-with-test-buffer ()
+    (plainer-c-mode)
+    (electric-layout-local-mode 1)
+    (electric-pair-local-mode 1)
+    (electric-indent-local-mode 1)
+    (setq-local electric-layout-rules
+                '((?\{ . (after))
+                  (?\} . (before))))
+    (insert "int main () ")
+    (let ((last-command-event ?\{))
+      (call-interactively (key-binding `[,last-command-event])))
+    (should (equal (buffer-string) "int main () {\n  \n}"))
+    ;; insert an additional newline and check indentation and
+    ;; reindentation
+    (call-interactively 'newline)
+    (should (equal (buffer-string) "int main () {\n\n  \n}"))))
+
 (define-derived-mode plainer-c-mode c-mode "pC"
   "A plainer/saner C-mode with no internal electric machinery."
   (c-toggle-electric-state -1)