Tramp: Don't offer non-existing containers in completion

* doc/misc/tramp.texi (File name completion):
Explain "completion-use-cache" property.

* lisp/net/tramp-cache.el (tramp-get-method-parameter): Declare.
(tramp-get-hash-table): Mark connection properties.
(tramp-dump-connection-properties): Remove empty lists.
(tramp-parse-connection-properties): Take connection property
"completion-use-cache" into account.  (Bug#76950)

* lisp/net/tramp-container.el (tramp-methods) <docker, dockercp, podman>
<podmancp, kubernetes, toolbox, distrobox, flatpak, apptainer, nspawn>:
Add `tramp-completion-use-cache' argument.

doc/misc/tramp.texi

@@ -3798,7 +3798,18 @@ completion lists.  If you want to suppress this completion because
 there are invalid entries in the persistency file, for example if the
 host configuration changes often, or if you plug your laptop to
 different networks frequently, you can set the user option
-@code{tramp-completion-use-cache} to @code{nil}.
+@code{tramp-completion-use-cache} to @code{nil}.  This is set per
+default for all container-based methods, like @option{docker} or
+@option{podman}.  If you want to suppress this for other connections,
+you can use the connection property @t{"completion-use-cache"},
+@xref{Predefined connection information}.  Example:
+
+@lisp
+@group
+(add-to-list 'tramp-connection-properties
+             (list "^/sshfs:" "completion-use-cache" nil))
+@end group
+@end lisp
 
 After remote host name completion comes completion of file names on
 the remote host.  It works the same as with local host file completion

lisp/net/tramp-cache.el

@@ -73,6 +73,9 @@
 ;;   `tramp-persistency-file-name', although being connection
 ;;   properties related to a `tramp-file-name' structure.
 ;;
+;; - Properties retrieved from `tramp-connection-properties' are not
+;;   saved in the file `tramp-persistency-file-name'.
+;;
 ;; - Reusable properties, which should not be saved, are kept in the
 ;;   process key retrieved by `tramp-get-process' (the main connection
 ;;   process).  Other processes could reuse these properties, avoiding
@@ -86,6 +89,8 @@
 (require 'tramp-compat)
 (require 'time-stamp)
 
+(declare-function tramp-get-method-parameter "tramp")
+
 ;;; -- Cache --
 
 ;;;###tramp-autoload
@@ -136,6 +141,7 @@ If it doesn't exist yet, it is created and initialized with
 matching entries of `tramp-connection-properties'.
 If KEY is `tramp-cache-undefined', don't create anything, and return nil."
   ;; (declare (tramp-suppress-trace t))
+  (let ((tramp-verbose 0))
     (unless (eq key tramp-cache-undefined)
       (or (gethash key tramp-cache-data)
 	  (let ((hash
@@ -145,8 +151,10 @@ If KEY is `tramp-cache-undefined', don't create anything, and return nil."
 		(when (string-match-p
 		       (or (nth 0 elt) "")
 		       (tramp-make-tramp-file-name key 'noloc))
-		(tramp-set-connection-property key (nth 1 elt) (nth 2 elt)))))
+		  ;; Mark it as taken from `tramp-connection-properties'.
-	  hash))))
+		  (tramp-set-connection-property
+		   key (propertize (nth 1 elt) 'tramp-default t) (nth 2 elt)))))
+	    hash)))))
 
 ;; We cannot use the `declare' form for `tramp-suppress-trace' in
 ;; autoloaded functions, because the tramp-loaddefs.el generation
@@ -596,9 +604,14 @@ PROPERTIES is a list of file properties (strings)."
 		    (not (tramp-file-name-localname key))
 		    (not (gethash "login-as" value))
 		    (not (gethash "started" value)))
+	       (progn
 		 (dolist (k (hash-table-keys value))
-		 (when (string-prefix-p " " k)
+		   ;; Suppress ephemeral properties.
+		   (when (or (string-prefix-p " " k)
+			     (get-text-property 0 'tramp-default k))
 		     (remhash k value)))
+		 (unless (hash-table-keys value)
+		   (remhash key cache)))
 	     (remhash key cache)))
 	 cache)
 	;; Dump it.
@@ -635,15 +648,17 @@ your laptop to different networks frequently."
   "Return a list of (user host) tuples allowed to access for METHOD.
 This function is added always in `tramp-get-completion-function'
 for all methods.  Resulting data are derived from connection history."
-  (and tramp-completion-use-cache
   (mapcar
    (lambda (key)
+     (let ((tramp-verbose 0))
        (and (tramp-file-name-p key)
 	    (string-equal method (tramp-file-name-method key))
 	    (not (tramp-file-name-localname key))
+	    (tramp-get-method-parameter
+	     key 'tramp-completion-use-cache tramp-completion-use-cache)
 	    (list (tramp-file-name-user key)
-		     (tramp-file-name-host key))))
+		  (tramp-file-name-host key)))))
-	(hash-table-keys tramp-cache-data))))
+   (hash-table-keys tramp-cache-data)))
 
 ;; When "emacs -Q" has been called, both variables are nil.  We do not
 ;; load the persistency file then, in order to have a clean test environment.

lisp/net/tramp-container.el

@@ -556,7 +556,8 @@ see its function help for a description of the format."
 		(tramp-direct-async (,tramp-default-remote-shell "-c"))
                 (tramp-remote-shell ,tramp-default-remote-shell)
                 (tramp-remote-shell-login ("-l"))
-                (tramp-remote-shell-args ("-i" "-c"))))
+                (tramp-remote-shell-args ("-i" "-c"))
+		(tramp-completion-use-cache nil)))
 
  (add-to-list 'tramp-methods
               `(,tramp-dockercp-method
@@ -573,7 +574,8 @@ see its function help for a description of the format."
 		(tramp-copy-program ,tramp-docker-program)
 		(tramp-copy-args (("cp")))
 		(tramp-copy-file-name (("%h" ":") ("%f")))
-                (tramp-copy-recursive t)))
+                (tramp-copy-recursive t)
+		(tramp-completion-use-cache nil)))
 
  (add-to-list 'tramp-methods
               `(,tramp-podman-method
@@ -586,7 +588,8 @@ see its function help for a description of the format."
 		(tramp-direct-async (,tramp-default-remote-shell "-c"))
                 (tramp-remote-shell ,tramp-default-remote-shell)
                 (tramp-remote-shell-login ("-l"))
-                (tramp-remote-shell-args ("-i" "-c"))))
+                (tramp-remote-shell-args ("-i" "-c"))
+		(tramp-completion-use-cache nil)))
 
  (add-to-list 'tramp-methods
               `(,tramp-podmancp-method
@@ -603,7 +606,8 @@ see its function help for a description of the format."
 		(tramp-copy-program ,tramp-podman-program)
 		(tramp-copy-args (("cp")))
 		(tramp-copy-file-name (("%h" ":") ("%f")))
-                (tramp-copy-recursive t)))
+                (tramp-copy-recursive t)
+		(tramp-completion-use-cache nil)))
 
  (add-to-list 'tramp-methods
               `(,tramp-kubernetes-method
@@ -618,7 +622,8 @@ see its function help for a description of the format."
 		(tramp-direct-async (,tramp-default-remote-shell "-c"))
                 (tramp-remote-shell ,tramp-default-remote-shell)
                 (tramp-remote-shell-login ("-l"))
-                (tramp-remote-shell-args ("-i" "-c"))))
+                (tramp-remote-shell-args ("-i" "-c"))
+		(tramp-completion-use-cache nil)))
 
  (add-to-list 'tramp-completion-multi-hop-methods tramp-docker-method)
  (add-to-list 'tramp-completion-multi-hop-methods tramp-podman-method)
@@ -674,7 +679,8 @@ see its function help for a description of the format."
 		 (tramp-direct-async (,tramp-default-remote-shell "-c"))
 		 (tramp-remote-shell ,tramp-default-remote-shell)
 		 (tramp-remote-shell-login ("-l"))
-		 (tramp-remote-shell-args ("-c"))))
+		 (tramp-remote-shell-args ("-c"))
+		 (tramp-completion-use-cache nil)))
 
   (add-to-list 'tramp-default-host-alist `(,tramp-toolbox-method nil ""))
   (add-to-list 'tramp-completion-multi-hop-methods tramp-toolbox-method)
@@ -695,7 +701,8 @@ see its function help for a description of the format."
 		 ;(tramp-direct-async (,tramp-default-remote-shell "-c"))
 		 (tramp-remote-shell ,tramp-default-remote-shell)
 		 (tramp-remote-shell-login ("-l"))
-		 (tramp-remote-shell-args ("-c"))))
+		 (tramp-remote-shell-args ("-c"))
+		 (tramp-completion-use-cache nil)))
 
   (add-to-list 'tramp-completion-multi-hop-methods tramp-distrobox-method)
 
@@ -719,7 +726,8 @@ see its function help for a description of the format."
 		 (tramp-direct-async (,tramp-default-remote-shell "-c"))
 		 (tramp-remote-shell ,tramp-default-remote-shell)
 		 (tramp-remote-shell-login ("-l"))
-		 (tramp-remote-shell-args ("-c"))))
+		 (tramp-remote-shell-args ("-c"))
+		 (tramp-completion-use-cache nil)))
 
   (add-to-list 'tramp-completion-multi-hop-methods tramp-flatpak-method)
 
@@ -750,7 +758,8 @@ see its function help for a description of the format."
 				    ("%h"))) ; Needed for multi-hop check.
 		 (tramp-remote-shell ,tramp-default-remote-shell)
 		 (tramp-remote-shell-login ("-l"))
-		 (tramp-remote-shell-args ("-c"))))
+		 (tramp-remote-shell-args ("-c"))
+		 (tramp-completion-use-cache nil)))
 
   (add-to-list 'tramp-completion-multi-hop-methods tramp-apptainer-method)
 
@@ -771,7 +780,8 @@ see its function help for a description of the format."
 				    ("%h")))
 		 (tramp-remote-shell ,tramp-default-remote-shell)
 		 (tramp-remote-shell-login ("-l"))
-		 (tramp-remote-shell-args ("-i" "-c"))))
+		 (tramp-remote-shell-args ("-i" "-c"))
+		 (tramp-completion-use-cache nil)))
 
   (add-to-list 'tramp-default-host-alist `(,tramp-nspawn-method nil ".host"))
   (add-to-list 'tramp-completion-multi-hop-methods tramp-nspawn-method)