Rename comint-fl-* to comint-fontify-input-* and mention it in NEWS

* lisp/comint.el
(comint-fontify-input-mode):
(comint--fontify-input-saved-jit-lock-contextually):
(comint--fontify-input-on):
(comint--fontify-input-off):
(comint--fontify-input-ppss-flush-indirect):
(comint--fontify-input-fontify-region): Replace comint-fl-* with
comint-fontify-input-*.

* lisp/ielm.el (ielm-fontify-input-enable):
(ielm-fontify-input-enable):
(ielm-indirect-setup-hook):
(inferior-emacs-lisp-mode): Replace comint-fl-* with
comint-fontify-input-*.

* lisp/shell.el (shell-comint-fl-enable):
(shell-mode): Replace comint-fl-* with comint-fontify-input-*.

* etc/NEWS: Mention the new modes and how to disable or enable
them (bug#58169).

4 files changed, 59 insertions, 44 deletions

diff --git a/etc/NEWS b/etc/NEWS
index d5aad9afc27..b9c4ef62ceb 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1214,6 +1214,14 @@ When nil, this prevents comint from deleting the current input when
 inserting previous input using '<mouse-2>'.  The default is t, to
 preserve past behavior.
 
+---
+*** New minor mode 'comint-fontify-input-mode'.
+This minor mode is enabled by default in "*shell*" and "*ielm*"
+buffers.  It fontifies input text according to 'shell-mode' or
+'emacs-lisp-mode' font-lock rules.  Customize the user options
+'shell-fontify-input-enable' and 'ielm-fontify-input-enable' to nil if
+you don't want to enable input fontification by default.
+
 ** Mwheel
 
 ---
@@ -2520,6 +2528,12 @@ behavior, customize the new 'eshell-lisp-form-nil-is-failure' option.
 Enabling this will automatically kill a "*shell*" buffer as soon as
 the shell session terminates.
 
+---
+*** New minor mode 'shell-highlight-undef-mode'
+Customize 'shell-highlight-undef-enable' to t if you want to enable
+this minor mode in "*shell*" buffers.  It will highlight undefined
+commands with a warning face as you type.
+
 ** Calc
 
 +++
diff --git a/lisp/comint.el b/lisp/comint.el
index 15c9388ea4f..a70a75c6487 100644
--- a/lisp/comint.el
+++ b/lisp/comint.el
@@ -1945,7 +1945,7 @@ Similarly for Soar, Scheme, etc."
               (when comint-highlight-input
                 (add-text-properties beg end
                                      '( font-lock-face comint-highlight-input
-                                        comint--fl-inhibit-fontification t
+                                        comint--fontify-input-inhibit-fontification t
                                         front-sticky t )))
               (unless comint-use-prompt-regexp
                 ;; Give old user input a field property of `input', to
@@ -3976,9 +3976,9 @@ fontification and other behavior of the indirect buffer."
 (defvar-local comint--indirect-buffer nil
   "Indirect buffer used for input fontification.")
 
-(defvar-local comint--fl-saved-jit-lock-contextually nil)
+(defvar-local comint--fontify-input-saved-jit-lock-contextually nil)
 
-(define-minor-mode comint-fl-mode
+(define-minor-mode comint-fontify-input-mode
   "Enable input fontification in the current comint buffer.
 This minor mode is useful if the current major mode derives from
 `comint-mode' and if `comint-indirect-setup-function' is set.
@@ -3993,71 +3993,71 @@ This function signals an error if `comint-use-prompt-regexp' is
 non-nil.  Input fontification isn't compatible with this
 setting."
   :lighter nil
-  (if comint-fl-mode
+  (if comint-fontify-input-mode
       (let ((success nil))
         (unwind-protect
             (progn
-              (comint--fl-on)
+              (comint--fontify-input-on)
               (setq success t))
           (unless success
-            (setq comint-fl-mode nil)
-            (comint--fl-off))))
-    (comint--fl-off)))
+            (setq comint-fontify-input-mode nil)
+            (comint--fontify-input-off))))
+    (comint--fontify-input-off)))
 
-(defun comint--fl-on ()
+(defun comint--fontify-input-on ()
   "Enable input fontification in the current comint buffer."
-  (comint--fl-off)
+  (comint--fontify-input-off)
 
   (when comint-use-prompt-regexp
     (error
      "Input fontification is incompatible with `comint-use-prompt-regexp'"))
 
   (add-function :around (local 'font-lock-fontify-region-function)
-                #'comint--fl-fontify-region)
+                #'comint--fontify-input-fontify-region)
   ;; `before-change-functions' are only run in the current buffer and
   ;; not in its indirect buffers, which means that we must manually
   ;; flush ppss cache
   (add-hook 'before-change-functions
-            #'comint--fl-ppss-flush-indirect 99 t)
+            #'comint--fontify-input-ppss-flush-indirect 99 t)
 
   ;; Set up contextual fontification
   (unless (booleanp jit-lock-contextually)
-    (setq comint--fl-saved-jit-lock-contextually
+    (setq comint--fontify-input-saved-jit-lock-contextually
           jit-lock-contextually)
     (setq-local jit-lock-contextually t)
     (when jit-lock-mode
       (jit-lock-mode t))))
 
-(defun comint--fl-off ()
+(defun comint--fontify-input-off ()
   "Disable input fontification in the current comint buffer."
   (remove-function (local 'font-lock-fontify-region-function)
-                   #'comint--fl-fontify-region)
+                   #'comint--fontify-input-fontify-region)
   (remove-hook 'before-change-functions
-               #'comint--fl-ppss-flush-indirect t)
+               #'comint--fontify-input-ppss-flush-indirect t)
 
   ;; Reset contextual fontification
-  (when comint--fl-saved-jit-lock-contextually
+  (when comint--fontify-input-saved-jit-lock-contextually
     (setq-local jit-lock-contextually
-                comint--fl-saved-jit-lock-contextually)
-    (setq comint--fl-saved-jit-lock-contextually nil)
+                comint--fontify-input-saved-jit-lock-contextually)
+    (setq comint--fontify-input-saved-jit-lock-contextually nil)
     (when jit-lock-mode
       (jit-lock-mode t)))
 
   (font-lock-flush))
 
-(defun comint--fl-ppss-flush-indirect (beg &rest rest)
+(defun comint--fontify-input-ppss-flush-indirect (beg &rest rest)
   (when-let ((buf (comint-indirect-buffer t)))
     (with-current-buffer buf
       (when (memq #'syntax-ppss-flush-cache before-change-functions)
         (apply #'syntax-ppss-flush-cache beg rest)))))
 
-(defun comint--fl-fontify-region (fun beg end verbose)
+(defun comint--fontify-input-fontify-region (fun beg end verbose)
   "Fontify process output and user input in the current comint buffer.
 First, fontify the region between BEG and END using FUN.  Then
 fontify only the input text in the region with the help of an
 indirect buffer.  VERBOSE is passed to the fontify-region
 functions.  Skip fontification of input regions with non-nil
-`comint--fl-inhibit-fontification' text property."
+`comint--fontify-input-inhibit-fontification' text property."
   (pcase (funcall fun beg end verbose)
     (`(jit-lock-bounds ,beg1 . ,end1)
      (setq beg beg1 end end1)))
@@ -4069,7 +4069,7 @@ functions.  Skip fontification of input regions with non-nil
           (comint--intersect-regions
            nil (lambda (beg end)
                  (unless (get-text-property
-                          beg 'comint--fl-inhibit-fontification)
+                          beg 'comint--fontify-input-inhibit-fontification)
                    (font-lock-fontify-region beg end verbose)))
            beg end)))
     (`((jit-lock-bounds ,beg1 . ,_) . (jit-lock-bounds ,_ . ,end1))
diff --git a/lisp/ielm.el b/lisp/ielm.el
index ad41cb1f6bd..fd41afa2437 100644
--- a/lisp/ielm.el
+++ b/lisp/ielm.el
@@ -474,11 +474,11 @@ nonempty, then flushes the buffer."
 
 ;;; Input fontification
 
-(defcustom ielm-comint-fl-enable t
+(defcustom ielm-fontify-input-enable t
   "Enable fontification of input in ielm buffers.
 This variable only has effect when creating an ielm buffer.  Use
-the command `comint-fl-mode' to toggle fontification of input in
-an already existing ielm buffer."
+the command `comint-fontify-input-mode' to toggle fontification
+of input in an already existing ielm buffer."
   :type 'boolean
   :safe 'booleanp
   :version "29.1")
@@ -556,8 +556,8 @@ Customized bindings may be defined in `ielm-map', which currently contains:
   :syntax-table emacs-lisp-mode-syntax-table
   :after-hook
   (and (null comint-use-prompt-regexp)
-       ielm-comint-fl-enable
-       (comint-fl-mode))
+       ielm-fontify-input-enable
+       (comint-fontify-input-mode))
 
   (setq comint-prompt-regexp (concat "^" (regexp-quote ielm-prompt)))
   (setq-local paragraph-separate "\\'")
diff --git a/lisp/shell.el b/lisp/shell.el
index 18bb3722427..641f274045d 100644
--- a/lisp/shell.el
+++ b/lisp/shell.el
@@ -308,10 +308,11 @@ for Shell mode only."
                  (const :tag "on" t))
   :group 'shell)
 
-(defcustom shell-comint-fl-enable t
+(defcustom shell-fontify-input-enable t
   "Enable fontification of input in shell buffers.
 This variable only has effect when the shell is started.  Use the
-command `comint-fl-mode' to toggle fontification of input."
+command `comint-fontify-input-mode' to toggle fontification of
+input."
   :type 'boolean
   :group 'shell
   :safe 'booleanp
@@ -623,8 +624,8 @@ command."
   :interactive nil
   :after-hook
   (unless comint-use-prompt-regexp
-    (if shell-comint-fl-enable
-        (comint-fl-mode))
+    (if shell-fontify-input-enable
+        (comint-fontify-input-mode))
     (if shell-highlight-undef-enable
         (shell-highlight-undef-mode)))
 
@@ -1664,8 +1665,8 @@ Similar to `executable-find', but use cache stored in
                       (if buf (buffer-local-value 'default-directory buf)
                         default-directory)))
                 (cond
-                 ;; Don't highlight command output.  Mostly useful if
-                 ;; `comint-fl-mode' is disabled.
+                 ;; Don't fontify command output.  Mostly useful if
+                 ;; `comint-fontify-input-mode' is disabled.
                  ((text-property-any beg (point) 'field 'output)
                   nil)
                  ((member cmd shell-highlight-undef-aliases)
@@ -1696,7 +1697,7 @@ Similar to `executable-find', but use cache stored in
 (define-minor-mode shell-highlight-undef-mode
   "Highlight undefined shell commands and aliases.
 This minor mode is mostly useful in `shell-mode' buffers and
-works better if `comint-fl-mode' is enabled."
+works better if `comint-fontify-input-mode' is enabled."
   :init-value nil
   (if shell--highlight-undef-indirect
       (progn
@@ -1706,7 +1707,7 @@ works better if `comint-fl-mode' is enabled."
           (with-current-buffer buf
             (font-lock-remove-keywords nil shell-highlight-undef-keywords))))
     (font-lock-remove-keywords nil shell-highlight-undef-keywords))
-  (remove-hook 'comint-fl-mode-hook
+  (remove-hook 'comint-fontify-input-mode-hook
                #'shell-highlight-undef-mode-restart t)
 
   (when shell-highlight-undef-mode
@@ -1722,9 +1723,9 @@ works better if `comint-fl-mode' is enabled."
             (concat
              "\\("
              "[;(){}`|&]"
-             (if comint-fl-mode
-                 ;; `comint-fl-mode' already puts point-min on end of
-                 ;; prompt
+             (if comint-fontify-input-mode
+                 ;; `comint-fontify-input-mode' already puts
+                 ;; point-min on end of prompt
                  ""
                (concat "\\|" comint-prompt-regexp))
              "\\|^"
@@ -1740,7 +1741,7 @@ works better if `comint-fl-mode' is enabled."
             (lambda ()
               (setq shell-highlight-undef-regexp regexp)
               (font-lock-add-keywords nil shell-highlight-undef-keywords t))))
-      (cond (comint-fl-mode
+      (cond (comint-fontify-input-mode
              (setq shell--highlight-undef-indirect setup)
              (if-let ((buf (comint-indirect-buffer t)))
                  (with-current-buffer buf
@@ -1748,7 +1749,7 @@ works better if `comint-fl-mode' is enabled."
                (add-hook 'comint-indirect-setup-hook setup nil t)))
             (t (funcall setup))))
 
-    (add-hook 'comint-fl-mode-hook
+    (add-hook 'comint-fontify-input-mode-hook
               #'shell-highlight-undef-mode-restart nil t))
 
   (font-lock-flush))
@@ -1756,9 +1757,9 @@ works better if `comint-fl-mode' is enabled."
 (defun shell-highlight-undef-mode-restart ()
   "If `shell-highlight-undef-mode' is on, restart it.
 `shell-highlight-undef-mode' performs its setup differently
-depending on `comint-fl-mode'.  It's useful to call this function
-when switching `comint-fl-mode' in order to make
-`shell-highlight-undef-mode' redo its setup."
+depending on `comint-fontify-input-mode'.  It's useful to call
+this function when switching `comint-fontify-input-mode' in order
+to make `shell-highlight-undef-mode' redo its setup."
   (when shell-highlight-undef-mode
     (shell-highlight-undef-mode 1)))