Rework setting local vars to be more robust using global minor mode

compiler-explorer.el

@@ -530,7 +530,7 @@ contents are replaced destructively and point is not preserved."
       (unless (eq major-mode 'compilation-mode)
         (compilation-mode)
         (setq buffer-undo-list t))
-      (compiler-explorer-mode +1)
+
       (when compiler-explorer--project-dir
         (setq-local default-directory compiler-explorer--project-dir)
         (setq-local compilation-parse-errors-filename-function
@@ -545,11 +545,9 @@ contents are replaced destructively and point is not preserved."
 This will write the list of supported compilers in the execution
 output buffer."
   (with-current-buffer (get-buffer-create compiler-explorer--exe-output-buffer)
-    (compiler-explorer-mode +1)
     (setq buffer-read-only t)
     (setq buffer-undo-list t)
-    (setq header-line-format
-          `(:eval (compiler-explorer--header-line-format-executor)))
+
     (let ((buffer-read-only nil)
           (keymap (make-keymap))
           (compiler (plist-get compiler-explorer--compiler-data :name))
@@ -581,11 +579,9 @@ output buffer."
   (pcase-let (((map :stdout :stderr :code) response))
     (with-current-buffer
         (get-buffer-create compiler-explorer--exe-output-buffer)
-      (compiler-explorer-mode +1)
       (setq buffer-read-only t)
       (setq buffer-undo-list t)
-      (setq header-line-format
-            `(:eval (compiler-explorer--header-line-format-executor)))
+
       (let ((buffer-read-only nil)
             (buf (current-buffer)))
         (with-temp-buffer
@@ -777,6 +773,7 @@ output buffer."
   (restore-buffer-modified-p nil))
 
 (defvar compiler-explorer--last-session)
+(defvar compiler-explorer-mode)
 
 (defun compiler-explorer--cleanup (&optional skip-save-session)
   "Kill current session.
@@ -837,7 +834,10 @@ If SKIP-SAVE-SESSION is non-nil, don't attempt to save the last session."
   (when compiler-explorer--project-dir
     (with-demoted-errors "compiler-explorer--cleanup: delete-directory: %s"
       (delete-directory compiler-explorer--project-dir t)))
-  (setq compiler-explorer--project-dir nil))
+  (setq compiler-explorer--project-dir nil)
+
+  (when compiler-explorer-mode
+    (compiler-explorer-mode -1)))
 
 
 ;; Source<->ASM overlays
@@ -1110,20 +1110,50 @@ It must have been created with `compiler-explorer--current-session'."
 (defvar compiler-explorer-mode-map (make-sparse-keymap)
   "Keymap used in `compiler-explorer-mode'.")
 
-(define-minor-mode compiler-explorer-mode
+(define-minor-mode compiler-explorer--local-mode
   "Minor mode used in compiler explorer buffers."
+  :interactive nil
   :lighter " CE"
   :keymap compiler-explorer-mode-map
   (cond
-   (compiler-explorer-mode
+   (compiler-explorer--local-mode
     (add-hook 'kill-buffer-hook #'compiler-explorer--cleanup nil t)
     (add-hook 'project-find-functions
-              #'compiler-explorer--project-find-function nil t))
+              #'compiler-explorer--project-find-function nil t)
+
+    (cond
+     ((eq (current-buffer) (get-buffer compiler-explorer--buffer))
+      (setq header-line-format
+            `(:eval (compiler-explorer--header-line-format-source)))
+      (add-hook 'after-change-functions
+                #'compiler-explorer--after-change nil t))
+     ((eq (current-buffer) (get-buffer compiler-explorer--compiler-buffer))
+      (setq header-line-format
+            `(:eval (compiler-explorer--header-line-format-compiler))))
+     ((eq (current-buffer) (get-buffer compiler-explorer--exe-output-buffer))
+      (setq header-line-format
+            `(:eval (compiler-explorer--header-line-format-executor))))))
    (t
     (remove-hook 'kill-buffer-hook #'compiler-explorer--cleanup t)
     (remove-hook 'project-find-functions
                  #'compiler-explorer--project-find-function t))))
 
+(defun compiler-explorer--local-mode-maybe-enable ()
+  "Enable `compiler-explorer--local-mode' if required."
+  (when (member (current-buffer)
+                (list
+                 (get-buffer compiler-explorer--buffer)
+                 (get-buffer compiler-explorer--compiler-buffer)
+                 (get-buffer compiler-explorer--output-buffer)
+                 (get-buffer compiler-explorer--exe-output-buffer)))
+    (compiler-explorer--local-mode +1)))
+
+(define-globalized-minor-mode compiler-explorer-mode
+  compiler-explorer--local-mode
+  compiler-explorer--local-mode-maybe-enable
+  (unless compiler-explorer-mode
+    (compiler-explorer--cleanup)))
+
 (defun compiler-explorer--define-menu ()
   "Define a menu in the menu bar for `compiler-explorer' commands."
   (easy-menu-define compiler-explorer-menu
@@ -1416,12 +1446,8 @@ execution."
     (with-current-buffer (get-buffer-create compiler-explorer--compiler-buffer)
       (asm-mode)
 
-      (compiler-explorer-mode +1)
-
       (setq buffer-read-only t)
       (setq buffer-undo-list t)
-      (setq header-line-format
-            `(:eval (compiler-explorer--header-line-format-compiler)))
 
       (compiler-explorer--request-async)
 
@@ -1602,7 +1628,7 @@ LAYOUT must be as described in `compiler-explorer-layouts'."
       (setq layout (% layout (length compiler-explorer-layouts)))
       (setq compiler-explorer--last-layout layout))
     (when (window-dedicated-p)
-      (unless compiler-explorer-mode
+      (unless compiler-explorer--local-mode
         (select-window (split-window-horizontally)))
       (set-window-dedicated-p (selected-window) nil))
     (delete-other-windows)
@@ -1686,6 +1712,7 @@ The source buffer is current when this hook runs.")
 This is a subr of `compiler-explorer-new-session' that uses given
 LANG, COMPILER, INTERACTIVE."
   (compiler-explorer--cleanup)
+  (compiler-explorer-mode +1)
   (when-let ((session compiler-explorer--last-session))
     (ring-insert compiler-explorer--session-ring session)
     (setq compiler-explorer--last-session nil))
@@ -1719,9 +1746,6 @@ LANG, COMPILER, INTERACTIVE."
                      (call-interactively #'compiler-explorer-set-compiler)
                    (signal (car err) (cdr err))))))
 
-      (setq header-line-format
-            `(:eval (compiler-explorer--header-line-format-source)))
-
       (when compiler-explorer-make-temp-file
         (setq compiler-explorer--project-dir
               (make-temp-file "compiler-explorer" 'dir))
@@ -1733,9 +1757,6 @@ LANG, COMPILER, INTERACTIVE."
 
       (compiler-explorer--define-menu)
 
-      (compiler-explorer-mode +1)
-      (add-hook 'after-change-functions
-                #'compiler-explorer--after-change nil t)
       (add-hook 'kill-emacs-hook #'compiler-explorer--save-sessions)
 
       (pop-to-buffer (current-buffer))