Extend Tramp external operations

* doc/misc/tramp.texi (New operations): Extend.

* lisp/net/tramp.el (tramp-file-name-for-operation-external):
Extend docstring.
(tramp-file-name-for-operation): Make more use of
`tramp-file-name-for-operation-external'.
(tramp-add-external-operation): Support ARG-TYPE `tramp-file-name'.

* test/lisp/net/tramp-tests.el (tramp-test49-external-backend-function):
Extend test.

doc/misc/tramp.texi

@@ -6973,7 +6973,7 @@ If the same @var{function} shall be used for different @value{tramp}
 backends, @code{tramp-add-external-operation} must be called for every
 backend, respectively.
 
-The optional argument @var{arg-type} specisfies, which argument of
+The optional argument @var{arg-type} specifies, which argument of
 @var{operation} shall be used in order to determine, whether the
 handler @var{function} should be called.  It can be
 
@@ -6988,6 +6988,10 @@ checked.  This is the default, if @var{arg-type} is @code{nil}.
 @item @code{process}@*
 @code{default-directory} of the process buffer of the first argument
 of @var{operation}, a process, is the remote file name to be checked.
+
+@item @code{tramp-file-name}@*
+The @code{tramp-file-name} structure of the first argument of
+@var{operation} is the remote file name to be checked.
 @end itemize
 
 If the first argument of @var{operation} is nil,
@@ -7015,6 +7019,26 @@ The example above could be changed like this:
 @end lisp
 @end defun
 
+@defun tramp-external-operation-p operation backend
+This checks, whether @value{tramp}'s backend @var{backend} supports
+external @var{operation}.  It returns the function registered as
+handler, or @code{nil}.  Example:
+
+@lisp
+@group
+(tramp-external-operation-p
+ #'my-test-operation 'tramp-sh)
+@result{} my-handle-test-operation
+@end group
+
+@group
+(tramp-external-operation-p
+ #'my-test-operation 'tramp-gvfs)
+@result{} nil
+@end group
+@end lisp
+@end defun
+
 @defun tramp-remove-external-operation operation backend
 The handler for @var{operation}, added by
 @code{tramp-add-external-operation}, is removed from @var{backend}.

lisp/net/tramp.el

@@ -2447,6 +2447,8 @@ symbol
   checked.
 - `process': `default-directory' of the process buffer of the first
   argument of OPERATION is the remote file name to be checked.
+- `tramp-file-name': the first argument of OPERATION, a
+  `tramp-file-name' structure, is the remote file name to be checked.
 
 If the first argument of OPERATION is nil, `default-directory' is the
 remote file name to be checked in case of `file' and `process'.
@@ -2500,8 +2502,10 @@ Must be handled by the callers."
     (if (and (stringp (nth 0 args)) (file-name-absolute-p (nth 0 args)))
 	(nth 0 args)
       default-directory))
+
    ;; STRING FILE.
    ((eq operation 'make-symbolic-link) (nth 1 args))
+
    ;; FILE DIRECTORY resp FILE1 FILE2.
    ((memq operation
 	  '(add-name-to-file copy-directory copy-file
@@ -2512,23 +2516,27 @@ Must be handled by the callers."
      ((tramp-tramp-file-p (nth 0 args)) (nth 0 args))
      ((file-name-absolute-p (nth 1 args)) (nth 1 args))
      (t default-directory)))
+
    ;; FILE DIRECTORY resp FILE1 FILE2.
    ((eq operation 'expand-file-name)
     (cond
      ((file-name-absolute-p (nth 0 args)) (nth 0 args))
      ((tramp-tramp-file-p (nth 1 args)) (nth 1 args))
      (t default-directory)))
+
    ;; START END FILE.
    ((eq operation 'write-region)
     (if (file-name-absolute-p (nth 2 args))
 	(nth 2 args)
       default-directory))
+
    ;; BUFFER.
    ((memq operation
 	  '(make-auto-save-file-name
 	    set-visited-file-modtime verify-visited-file-modtime))
     (buffer-file-name
      (if (bufferp (nth 0 args)) (nth 0 args) (current-buffer))))
+
    ;; COMMAND.
    ((or
      (memq operation
@@ -2541,6 +2549,7 @@ Must be handled by the callers."
      (eq (alist-get operation tramp-file-name-for-operation-external)
 	 'default-directory))
     default-directory)
+
    ;; PROC or BUFFER.
    ((or
      (memq operation '(file-notify-rm-watch file-notify-valid-p))
@@ -2557,16 +2566,25 @@ Must be handled by the callers."
 		    (or (get-process (nth 0 args)) (get-buffer (nth 0 args)))))))
 	  (tramp-get-default-directory buf))
 	""))
+
    ;; VEC.
-   ((memq operation
+   ((or
-	  '(tramp-get-home-directory tramp-get-remote-gid
+     (memq operation
-	    tramp-get-remote-groups tramp-get-remote-uid))
+	   '(tramp-get-home-directory tramp-get-remote-gid
-    (tramp-make-tramp-file-name (nth 0 args)))
+	     tramp-get-remote-groups tramp-get-remote-uid))
+     (eq (alist-get operation tramp-file-name-for-operation-external)
+	 'tramp-file-name))
+    (or
+     (and (tramp-file-name-p (nth 0 args))
+	  (tramp-make-tramp-file-name (nth 0 args)))
+     ""))
+
    ;; A function.
    ((functionp (alist-get operation tramp-file-name-for-operation-external))
     (apply
      (alist-get operation tramp-file-name-for-operation-external)
      operation args))
+
    ;; Unknown file primitive.
    (t (unless (memq 'remote-file-error debug-ignored-errors)
 	(tramp-error
@@ -2601,17 +2619,17 @@ OPERATION must not be one of the magic operations listed in Info
 node `(elisp) Magic File Names'.  FUNCTION must have the same argument
 list as OPERATION.  BACKEND, a symbol, must be one of the Tramp backend
 packages like `tramp-sh' (except `tramp-ftp').  ARG-TYPE is either
-`file' (the default), `default-directory', `process' or a function
+`file' (the default), `default-directory', `process', `tramp-file-name',
-symbol.  It describes the type of the OPERATION argument to be checked.
+or a function symbol.  It describes the type of the OPERATION argument
-See the docstring of `tramp-file-name-for-operation-external' for its
+to be checked.  See the docstring of
-meaning."
+`tramp-file-name-for-operation-external' for its meaning."
   (require backend)
   (when-let* ((fnha
 	       (intern-soft
 		(concat (symbol-name backend) "-file-name-handler-alist")))
 	      ((boundp fnha))
 	      (arg-type (or arg-type 'file)))
-    (unless (or (memq arg-type '(file default-directory process))
+    (unless (or (memq arg-type '(file default-directory process tramp-file-name))
 		(functionp arg-type))
       (tramp-error nil 'remote-file-error "Unknown arg type: %s" arg-type))
     ;; Make BACKEND aware of the new operation.
@@ -2635,6 +2653,15 @@ meaning."
 	    (apply orig-fun args)))
        `((name . ,(concat "tramp-advice-" (symbol-name operation))))))))
 
+(defun tramp-external-operation-p (operation backend)
+  "Check, whether Tramp BACKEND supports external OPERATION.
+It returns the function registered as handler, or nil."
+  (and-let* ((fnha
+	      (intern-soft
+	       (concat (symbol-name backend) "-file-name-handler-alist")))
+	     ((boundp fnha))
+	     ((alist-get operation (symbol-value fnha))))))
+
 (defun tramp-remove-external-operation (operation backend)
   "Remove OPERATION from Tramp BACKEND as handler for OPERATION.
 OPERATION must not be one of the magic operations listed in Info
@@ -4264,9 +4291,8 @@ Let-bind it when necessary.")
             (tramp-get-connection-property vec "~"))))
     (when home-dir
       (setq home-dir
-	    (tramp-compat-funcall
+	    (tramp-compat-funcall 'directory-abbrev-apply
-	     'directory-abbrev-apply
+	      (tramp-make-tramp-file-name vec home-dir))))
-	     (tramp-make-tramp-file-name vec home-dir))))
     ;; If any elt of `directory-abbrev-alist' matches this name,
     ;; abbreviate accordingly.
     (setq filename (tramp-compat-funcall 'directory-abbrev-apply filename))
@@ -4864,22 +4890,21 @@ existing) are returned."
 		      (setq remote-copy (tramp-make-tramp-temp-file v))
 		      ;; This is defined in tramp-sh.el.  Let's assume
 		      ;; this is loaded already.
-		      (tramp-compat-funcall
+		      (tramp-compat-funcall 'tramp-send-command
-		       'tramp-send-command
+			v
-		       v
+			(cond
-		       (cond
+			 ((and beg end)
-			((and beg end)
+			  (format "dd bs=1 skip=%d if=%s count=%d of=%s"
-			 (format "dd bs=1 skip=%d if=%s count=%d of=%s"
+				  beg (tramp-shell-quote-argument localname)
-				 beg (tramp-shell-quote-argument localname)
+				  (- end beg) remote-copy))
-				 (- end beg) remote-copy))
+			 (beg
-			(beg
+			  (format "dd bs=1 skip=%d if=%s of=%s"
-			 (format "dd bs=1 skip=%d if=%s of=%s"
+				  beg (tramp-shell-quote-argument localname)
-				 beg (tramp-shell-quote-argument localname)
+				  remote-copy))
-				 remote-copy))
+			 (end
-			(end
+			  (format "dd bs=1 count=%d if=%s of=%s"
-			 (format "dd bs=1 count=%d if=%s of=%s"
+				  end (tramp-shell-quote-argument localname)
-				 end (tramp-shell-quote-argument localname)
+				  remote-copy))))
-				 remote-copy))))
 		      (setq tramp-temp-buffer-file-name nil beg nil end nil))
 
 		    ;; `insert-file-contents-literally' takes care to
@@ -5565,12 +5590,10 @@ processes."
 		(tramp-compat-make-temp-name))))
 	   (options
 	    (when sh-file-name-handler-p
-	      (tramp-compat-funcall
+	      (tramp-compat-funcall 'tramp-ssh-controlmaster-options v)))
-		  'tramp-ssh-controlmaster-options v)))
 	   (device
 	    (when adb-file-name-handler-p
-	      (tramp-compat-funcall
+	      (tramp-compat-funcall 'tramp-adb-get-device v)))
-		  'tramp-adb-get-device v)))
            (pta (unless (eq connection-type 'pipe) "-t"))
 	   login-args p)
 
@@ -7475,13 +7498,12 @@ name of a process or buffer, or nil to default to the current buffer."
 	;; This is for tramp-sh.el.  Other backends do not support this (yet).
 	;; Not all "kill" implementations support process groups by
 	;; negative pid, so we try both variants.
-	(tramp-compat-funcall
+	(tramp-compat-funcall 'tramp-send-command
-	 'tramp-send-command
+	  (process-get proc 'tramp-vector)
-	 (process-get proc 'tramp-vector)
+	  (format "(\\kill -2 -%d || \\kill -2 %d) 2>%s"
-	 (format "(\\kill -2 -%d || \\kill -2 %d) 2>%s"
+                  pid pid
-                 pid pid
+                  (tramp-get-remote-null-device
-                 (tramp-get-remote-null-device
+		   (process-get proc 'tramp-vector))))
-		  (process-get proc 'tramp-vector))))
 	;; Wait, until the process has disappeared.  If it doesn't,
 	;; fall back to the default implementation.
         (while (tramp-accept-process-output proc))
@@ -7531,9 +7553,8 @@ SIGCODE may be an integer, or a symbol whose name is a signal name."
       (tramp-message
        vec 5 "Send signal %s to process %s with pid %s" sigcode process pid)
       ;; This is for tramp-sh.el.  Other backends do not support this (yet).
-      (if (tramp-compat-funcall
+      (if (tramp-compat-funcall 'tramp-send-command-and-check
-           'tramp-send-command-and-check
+            vec (format "\\kill -%s %d" sigcode pid))
-           vec (format "\\kill -%s %d" sigcode pid))
           0 -1))))
 
 ;; `signal-process-functions' exists since Emacs 29.1.

test/lisp/net/tramp-tests.el

@@ -8920,6 +8920,9 @@ process sentinels.  They shall not disturb each other."
 	  (intern
 	   (string-remove-suffix
 	    "-file-name-handler" (symbol-name file-name-handler)))))
+    ;; Cleanup.
+    (tramp-remove-external-operation #'tramp--test-operation backend)
+    (tramp-remove-external-operation #'process-id backend)
 
     ;; There is no backend specific code.
     (should-not
@@ -8950,6 +8953,9 @@ process sentinels.  They shall not disturb each other."
     ;; This doesn't hurt.
     (tramp-add-external-operation
      #'tramp--test-operation #'tramp--handle-test-operation backend 'file)
+    (should
+     (eq #'tramp--handle-test-operation
+	 (tramp-external-operation-p #'tramp--test-operation backend)))
 
     ;; The backend specific function is called.
     (should
@@ -8977,6 +8983,7 @@ process sentinels.  They shall not disturb each other."
 
     (tramp-remove-external-operation #'tramp--test-operation backend)
     ;; There is no backend specific code.
+    (should-not (tramp-external-operation-p #'tramp--test-operation backend))
     (should-not
      (string-equal (tramp--test-operation ert-remote-temporary-file-directory)
 		   (tramp--handle-test-operation
@@ -9004,6 +9011,9 @@ process sentinels.  They shall not disturb each other."
     (tramp-add-external-operation
      #'tramp--test-operation #'tramp--handle-test-operation
      backend 'default-directory)
+    (should
+     (eq #'tramp--handle-test-operation
+	 (tramp-external-operation-p #'tramp--test-operation backend)))
 
     ;; The backend specific function is called.
     (let ((default-directory ert-remote-temporary-file-directory))
@@ -9017,6 +9027,7 @@ process sentinels.  They shall not disturb each other."
 
     (tramp-remove-external-operation #'tramp--test-operation backend)
     ;; There is no backend specific code.
+    (should-not (tramp-external-operation-p #'tramp--test-operation backend))
     (let ((default-directory ert-remote-temporary-file-directory))
       (should-not
        (string-equal (tramp--test-operation)
@@ -9048,16 +9059,48 @@ process sentinels.  They shall not disturb each other."
 	      (should (natnump (setq id (process-id proc))))
 	      (tramp-add-external-operation
 	       #'process-id #'tramp--handle-process-id backend 'process)
+	      (should
+	       (eq #'tramp--handle-process-id
+		   (tramp-external-operation-p #'process-id backend)))
 	      (should (= (process-id proc) (1+ id))))
 
 	  ;; Cleanup.
 	  (tramp-remove-external-operation #'process-id backend)
+	  (should-not (tramp-external-operation-p #'process-id backend))
 	  (ignore-errors (delete-process proc)))))
 
+    ;; Test `tramp-file-name' arg type.
+    (tramp-add-external-operation
+     #'tramp--test-operation #'tramp--handle-test-operation
+     backend 'tramp-file-name)
+    (should
+     (eq #'tramp--handle-test-operation
+	 (tramp-external-operation-p #'tramp--test-operation backend)))
+
+    ;; The backend specific function is called.
+    (should
+     (string-equal (tramp--test-operation tramp-test-vec)
+		   (tramp--handle-test-operation tramp-test-vec)))
+    (let ((vec (copy-tramp-file-name tramp-test-vec)))
+      (setf (tramp-file-name-method vec) (if (tramp--test-sh-p) "sftp" "sudo"))
+      (should-not
+       (string-equal (tramp--test-operation vec)
+		     (tramp--handle-test-operation vec))))
+
+    (tramp-remove-external-operation #'tramp--test-operation backend)
+    ;; There is no backend specific code.
+    (should-not (tramp-external-operation-p #'tramp--test-operation backend))
+    (should-not
+     (string-equal (tramp--test-operation tramp-test-vec)
+		   (tramp--handle-test-operation tramp-test-vec)))
+
     ;; Test function arg type.
     (tramp-add-external-operation
      #'tramp--test-operation #'tramp--handle-test-operation
      backend #'tramp--test-operation-file-name-for-operation)
+    (should
+     (eq #'tramp--handle-test-operation
+	 (tramp-external-operation-p #'tramp--test-operation backend)))
 
     ;; The backend specific function is called.
     (let ((default-directory ert-remote-temporary-file-directory))
@@ -9071,6 +9114,7 @@ process sentinels.  They shall not disturb each other."
 
     (tramp-remove-external-operation #'tramp--test-operation backend)
     ;; There is no backend specific code.
+    (should-not (tramp-external-operation-p #'tramp--test-operation backend))
     (let ((default-directory ert-remote-temporary-file-directory))
       (should-not
        (string-equal (tramp--test-operation)