Simplify Tramp's find-executable

* lisp/net/tramp-cache.el (with-tramp-saved-connection-property):
Fix typo.

* lisp/net/tramp-compat.el: Add TODO.

* lisp/net/tramp-sh.el (tramp-find-executable): Simplify, using
"type -P ...".
(tramp-set-remote-path): Better handling of superlong $PATH.
(tramp-get-remote-path): Adapt/use connection properties.

* test/lisp/net/tramp-tests.el (tramp--test-enabled)
(tramp-test03-file-name-host-rules): Don't wrap
`tramp-cleanup-connection' with `ignore-errors'.

lisp/net/tramp-cache.el

@@ -482,10 +482,10 @@ used to cache connection properties of the local machine."
 	  (hash (tramp-get-hash-table key))
 	  (cached (and (hash-table-p hash)
 		       (gethash ,property hash tramp-cache-undefined))))
-     (tramp-message key 7 "Saved %s %s" property cached)
+     (tramp-message key 7 "Saved %s %s" ,property cached)
      (unwind-protect (progn ,@body)
        ;; Reset PROPERTY.  Recompute hash, it could have been flushed.
-       (tramp-message key 7 "Restored %s %s" property cached)
+       (tramp-message key 7 "Restored %s %s" ,property cached)
        (setq hash (tramp-get-hash-table key))
        (if (not (eq cached tramp-cache-undefined))
 	   (puthash ,property cached hash)

lisp/net/tramp-compat.el

@@ -245,6 +245,8 @@ value is the default binding of the variable."
 ;;
 ;; * Use `with-environment-variables'.
 ;;
+;; * Use `ensure-list'.
+;;
 ;; * Starting with Emacs 29.1, use `buffer-match-p'.
 ;;
 ;; * Starting with Emacs 29.1, use `string-split'.

lisp/net/tramp-sh.el

@@ -4092,18 +4092,8 @@ Returns the absolute file name of PROGNAME, if found, and nil otherwise.
 
 This function expects to be in the right *tramp* buffer."
   (with-current-buffer (tramp-get-connection-buffer vec)
-    (let (result)
-      ;; Check whether the executable is in $PATH.  "which(1)" does not
-      ;; report always a correct error code; therefore we check the
-      ;; number of words it returns.  "SunOS 5.10" (and maybe "SunOS
-      ;; 5.11") have problems with this command, we disable the call
-      ;; therefore.
-      (unless (or ignore-path (tramp-check-remote-uname vec tramp-sunos-unames))
-	(tramp-send-command vec (format "which \\%s | wc -w" progname))
-	(goto-char (point-min))
-	(if (looking-at-p (rx bol (* blank) "1" eol))
-	    (setq result (concat "\\" progname))))
-      (unless result
+    (unless ignore-path
+      (setq dirlist (cons "$PATH" dirlist)))
     (when ignore-tilde
       ;; Remove all ~/foo directories from dirlist.
       (let (newdl d)
@@ -4114,22 +4104,11 @@ This function expects to be in the right *tramp* buffer."
 	    (setq newdl (cons d newdl))))
 	(setq dirlist (nreverse newdl))))
     (tramp-send-command
-	 vec
-	 (format (concat "while read d; "
-			 "do if test -x $d/%s && test -f $d/%s; "
-			 "then echo tramp_executable $d/%s; "
-			 "break; fi; done <<'%s'\n"
-			 "%s\n%s")
-		 progname progname progname
-		 tramp-end-of-heredoc
-		 (string-join dirlist "\n")
-		 tramp-end-of-heredoc))
-	(goto-char (point-max))
-	(when (search-backward "tramp_executable " nil t)
-	  (skip-chars-forward "^ ")
-	  (skip-chars-forward " ")
-	  (setq result (buffer-substring (point) (line-end-position)))))
-    result)))
+     vec (format "%s type -P %s 2>%s"
+		 (if dirlist (concat "PATH=" (string-join dirlist ":")) "")
+		 progname (tramp-get-remote-null-device vec)))
+    (unless (zerop (buffer-size))
+      (string-trim (buffer-string)))))
 
 ;; On hydra.nixos.org, the $PATH environment variable is too long to
 ;; send it.  This is likely not due to PATH_MAX, but PIPE_BUF.  We
@@ -4151,6 +4130,12 @@ variable PATH."
       ;; Use a temporary file.  We cannot use `write-region' because
       ;; setting the remote path happens in the early connection
       ;; handshake, and not all external tools are determined yet.
+      ;; Furthermore, we know that the COMMAND is too long, due to a
+      ;; very long remote-path.  Set it temporarily to something
+      ;; short.
+      (with-tramp-saved-connection-property (tramp-get-process vec) "remote-path"
+	(tramp-set-connection-property
+	 (tramp-get-process vec) "remote-path" '("/bin" "/usr/bin"))
 	(setq command (concat command "\n")
 	      tmpfile (tramp-make-tramp-temp-file vec))
 	(while (not (string-empty-p command))
@@ -4162,7 +4147,7 @@ variable PATH."
 				   (tramp-shell-quote-argument chunk)
 				   (tramp-shell-quote-argument tmpfile))))
 	(tramp-send-command vec (format ". %s" tmpfile))
-      (tramp-send-command vec (format "rm -f %s" tmpfile)))))
+	(tramp-send-command vec (format "rm -f %s" tmpfile))))))
 
 ;; ------------------------------------------------------------
 ;; -- Communication with external shell --
@@ -5569,25 +5554,21 @@ Nonexistent directories are removed from spec."
   (with-current-buffer (tramp-get-connection-buffer vec)
     ;; Expand connection-local variables.
     (tramp-set-connection-local-variables vec)
-    (with-tramp-connection-property
-	;; When `tramp-own-remote-path' is in `tramp-remote-path', we
-	;; cache the result for the session only.  Otherwise, the
-	;; result is cached persistently.
-	(if (memq 'tramp-own-remote-path tramp-remote-path)
-	    (tramp-get-process vec) vec)
-	"remote-path"
+    (with-tramp-connection-property (tramp-get-process vec) "remote-path"
       (let* ((remote-path (copy-tree tramp-remote-path))
 	     (elt1 (memq 'tramp-default-remote-path remote-path))
 	     (elt2 (memq 'tramp-own-remote-path remote-path))
 	     (default-remote-path
 	      (when elt1
 		(or
+		 (with-tramp-connection-property
+		     (tramp-get-process vec) "default-remote-path"
 		   (tramp-send-command-and-read
 		    vec
                     (format
                      "echo \\\"`getconf PATH 2>%s`\\\""
                      (tramp-get-remote-null-device vec))
-                   'noerror)
+                    'noerror))
 		 ;; Default if "getconf" is not available.
 		 (progn
 		   (tramp-message
@@ -5600,6 +5581,8 @@ Nonexistent directories are removed from spec."
 	      ;; string.  So we use `tramp-end-of-heredoc' as marker.
 	      (when elt2
 		(or
+		 (with-tramp-connection-property
+		     (tramp-get-process vec) "own-remote-path"
 		   (tramp-send-command-and-read
 		    vec
 		    (format
@@ -5612,7 +5595,7 @@ Nonexistent directories are removed from spec."
 		      (tramp-get-method-parameter vec 'tramp-remote-shell-args)
 		      " ")
 		     (tramp-shell-quote-argument tramp-end-of-heredoc))
-		  'noerror (rx (literal tramp-end-of-heredoc)))
+		    'noerror (rx (literal tramp-end-of-heredoc))))
 		 (progn
 		   (tramp-warning
 		    vec "Could not retrieve `tramp-own-remote-path'")

test/lisp/net/tramp-tests.el

@@ -282,8 +282,7 @@ being the result.")
 		(delete-directory file 'recursive)
 	      (delete-file file))))))
     ;; Cleanup connection.
-    (ignore-errors
-      (tramp-cleanup-connection tramp-test-vec nil 'keep-password)))
+    (tramp-cleanup-connection tramp-test-vec nil 'keep-password))
 
   ;; Return result.
   (cdr tramp--test-enabled-checked))
@@ -2175,8 +2174,7 @@ being the result.")
   (dolist (m '("su" "sg" "sudo" "doas" "ksu"))
     (when (assoc m tramp-methods)
       (let (tramp-connection-properties tramp-default-proxies-alist)
-	(ignore-errors
-	  (tramp-cleanup-connection tramp-test-vec 'keep-debug 'keep-password))
+	(tramp-cleanup-connection tramp-test-vec 'keep-debug 'keep-password)
 	;; Single hop.  The host name must match `tramp-local-host-regexp'.
 	(should-error
 	 (find-file (format "/%s:foo:" m))