Move several completions from eshell to pcomplete (Bug#10585)

* lisp/eshell/em-unix.el (eshell-complete-hostname)
(pcomplete/ftp, pcomplete/ncftp, pcomplete/ping)
(pcomplete/rlogin, pcomplete/telnet, pcomplete/rsh):
Move from here...
* lisp/pcmpl-unix.el (pcmpl-unix-complete-hostname)
(pcomplete/ftp, pcomplete/ncftp, pcomplete/ping)
(pcomplete/rlogin, pcomplete/telnet, pcomplete/rsh):
...to here.  Make old names into aliases.

* lisp/eshell/esh-util.el (eshell-hosts-file)
(eshell-host-names, eshell-host-timestamp)
(eshell-read-hosts-file, eshell-read-hosts)
(eshell-read-host-names): Move from here...
* lisp/pcomplete.el (pcomplete-hosts-file)
(pcomplete--host-name-cache)
(pcomplete--host-name-cache-timestamp)
(pcomplete-read-hosts-file, pcomplete-read-hosts)
(pcomplete-read-host-names): ...to here.  Make old names into
aliases.

* lisp/eshell/em-unix.el (eshell-complete-host-reference): Update
caller.

4 files changed, 94 insertions, 59 deletions

diff --git a/lisp/eshell/em-unix.el b/lisp/eshell/em-unix.el
index fbd3cfbb6fc..fd4cd6716d2 100644
--- a/lisp/eshell/em-unix.el
+++ b/lisp/eshell/em-unix.el
@@ -787,9 +787,9 @@ external command."
 
 ;; completions rules for some common UNIX commands
 
-(defsubst eshell-complete-hostname ()
-  "Complete a command that wants a hostname for an argument."
-  (pcomplete-here (eshell-read-host-names)))
+(autoload 'pcmpl-unix-complete-hostname "pcmpl-unix")
+(define-obsolete-function-alias 'eshell-complete-hostname
+  #'pcmpl-unix-complete-hostname "28.1")
 
 (defun eshell-complete-host-reference ()
   "If there is a host reference, complete it."
@@ -798,26 +798,7 @@ external command."
     (when (setq index (string-match "@[a-z.]*\\'" arg))
       (setq pcomplete-stub (substring arg (1+ index))
             pcomplete-last-completion-raw t)
-      (throw 'pcomplete-completions (eshell-read-host-names)))))
-
-(defalias 'pcomplete/ftp    'eshell-complete-hostname)
-(defalias 'pcomplete/ncftp  'eshell-complete-hostname)
-(defalias 'pcomplete/ping   'eshell-complete-hostname)
-(defalias 'pcomplete/rlogin 'eshell-complete-hostname)
-
-(defun pcomplete/telnet ()
-  (require 'pcmpl-unix)
-  (pcomplete-opt "xl(pcmpl-unix-user-names)")
-  (eshell-complete-hostname))
-
-(defun pcomplete/rsh ()
-  "Complete `rsh', which, after the user and hostname, is like xargs."
-  (require 'pcmpl-unix)
-  (pcomplete-opt "l(pcmpl-unix-user-names)")
-  (eshell-complete-hostname)
-  (pcomplete-here (funcall pcomplete-command-completion-function))
-  (funcall (or (pcomplete-find-completion-function (pcomplete-arg 1))
-               pcomplete-default-completion-function)))
+      (throw 'pcomplete-completions (pcomplete-read-host-names)))))
 
 (defvar block-size)
 (defvar by-bytes)
diff --git a/lisp/eshell/esh-util.el b/lisp/eshell/esh-util.el
index ab030ede05b..0122f9be488 100644
--- a/lisp/eshell/esh-util.el
+++ b/lisp/eshell/esh-util.el
@@ -51,9 +51,15 @@ similarly to external commands, as far as successful result output."
   :group 'eshell-util)
 
 (defcustom eshell-hosts-file "/etc/hosts"
-  "The name of the /etc/hosts file."
+  "The name of the /etc/hosts file.
+Use `pcomplete-hosts-file' instead; this variable is obsolete and
+has no effect."
   :type '(choice (const :tag "No hosts file" nil) file)
   :group 'eshell-util)
+;; Don't make it into an alias, because it doesn't really work with
+;; custom and risks creating duplicate entries.  Just point users to
+;; the other variable, which is less frustrating.
+(make-obsolete-variable 'eshell-hosts-file nil "28.1")
 
 (defcustom eshell-handle-errors t
   "If non-nil, Eshell will handle errors itself.
@@ -127,11 +133,14 @@ function `string-to-number'."
 (defvar eshell-user-timestamp nil
   "A timestamp of when the user file was read.")
 
-(defvar eshell-host-names nil
-  "A cache the names of frequently accessed hosts.")
+;;; Obsolete variables:
 
-(defvar eshell-host-timestamp nil
-  "A timestamp of when the hosts file was read.")
+(define-obsolete-variable-alias 'eshell-host-names
+  'pcomplete--host-name-cache "28.1")
+(define-obsolete-variable-alias 'eshell-host-timestamp
+  'pcomplete--host-name-cache-timestamp "28.1")
+(defvar pcomplete--host-name-cache)
+(defvar pcomplete--host-name-cache-timestamp)
 
 ;;; Functions:
 
@@ -479,37 +488,15 @@ list."
 
 (defalias 'eshell-user-name 'user-login-name)
 
-(defun eshell-read-hosts-file (filename)
-  "Read in the hosts from FILENAME, default `eshell-hosts-file'."
-  (let (hosts)
-    (with-temp-buffer
-      (insert-file-contents (or filename eshell-hosts-file))
-      (goto-char (point-min))
-      (while (re-search-forward
-              ;; "^ \t\\([^# \t\n]+\\)[ \t]+\\([^ \t\n]+\\)\\([ \t]*\\([^ \t\n]+\\)\\)?"
-              "^[ \t]*\\([^# \t\n]+\\)[ \t]+\\([^ \t\n].+\\)" nil t)
-        (push (cons (match-string 1)
-                    (split-string (match-string 2)))
-              hosts)))
-    (nreverse hosts)))
-
-(defun eshell-read-hosts (file result-var timestamp-var)
-  "Read the contents of /etc/hosts for host names."
-  (if (or (not (symbol-value result-var))
-          (not (symbol-value timestamp-var))
-          (time-less-p
-           (symbol-value timestamp-var)
-           (file-attribute-modification-time (file-attributes file))))
-      (progn
-        (set result-var (apply #'nconc (eshell-read-hosts-file file)))
-        (set timestamp-var (current-time))))
-  (symbol-value result-var))
-
-(defun eshell-read-host-names ()
-  "Read the contents of /etc/hosts for host names."
-  (if eshell-hosts-file
-      (eshell-read-hosts eshell-hosts-file 'eshell-host-names
-                         'eshell-host-timestamp)))
+(autoload 'pcomplete-read-hosts-file "pcomplete")
+(autoload 'pcomplete-read-hosts "pcomplete")
+(autoload 'pcomplete-read-host-names "pcomplete")
+(define-obsolete-function-alias 'eshell-read-hosts-file
+  #'pcomplete-read-hosts-file "28.1")
+(define-obsolete-function-alias 'eshell-read-hosts
+  #'pcomplete-read-hosts "28.1")
+(define-obsolete-function-alias 'eshell-read-host-names
+  #'pcomplete-read-host-names "28.1")
 
 (defsubst eshell-copy-environment ()
   "Return an unrelated copy of `process-environment'."
diff --git a/lisp/pcmpl-unix.el b/lisp/pcmpl-unix.el
index 822f6f37e78..74f45b95233 100644
--- a/lisp/pcmpl-unix.el
+++ b/lisp/pcmpl-unix.el
@@ -217,6 +217,29 @@ Includes files as well as host names followed by a colon."
                                        (pcmpl-ssh-hosts)))))))
                 (complete-with-action action table string pred))))))
 
+(defsubst pcmpl-unix-complete-hostname ()
+  "Complete a command that wants a hostname for an argument."
+  (pcomplete-here (pcomplete-read-host-names)))
+
+(defalias 'pcomplete/ftp    'pcmpl-unix-complete-hostname)
+(defalias 'pcomplete/ncftp  'pcmpl-unix-complete-hostname)
+(defalias 'pcomplete/ping   'pcmpl-unix-complete-hostname)
+(defalias 'pcomplete/rlogin 'pcmpl-unix-complete-hostname)
+
+;;;###autoload
+(defun pcomplete/telnet ()
+  (pcomplete-opt "xl(pcmpl-unix-user-names)")
+  (pcmpl-unix-complete-hostname))
+
+;;;###autoload
+(defun pcomplete/rsh ()
+  "Complete `rsh', which, after the user and hostname, is like xargs."
+  (pcomplete-opt "l(pcmpl-unix-user-names)")
+  (pcmpl-unix-complete-hostname)
+  (pcomplete-here (funcall pcomplete-command-completion-function))
+  (funcall (or (pcomplete-find-completion-function (pcomplete-arg 1))
+               pcomplete-default-completion-function)))
+
 (provide 'pcmpl-unix)
 
 ;;; pcmpl-unix.el ends here
diff --git a/lisp/pcomplete.el b/lisp/pcomplete.el
index 32e61e84e0d..014f9628b99 100644
--- a/lisp/pcomplete.el
+++ b/lisp/pcomplete.el
@@ -325,6 +325,10 @@ already terminated by a character, this variable should be locally
 modified to be an empty string, or the desired separation string."
   :type 'string)
 
+(defcustom pcomplete-hosts-file "/etc/hosts"
+  "The name of the /etc/hosts file."
+  :type '(choice (const :tag "No hosts file" nil) file))
+
 ;;; Internal Variables:
 
 ;; for cycling completion support
@@ -1289,6 +1293,46 @@ If specific documentation can't be given, be generic."
     (skip-chars-backward "\n")
     (buffer-substring (point-min) (point))))
 
+;; hostname completion
+
+(defvar pcomplete--host-name-cache nil
+  "A cache the names of frequently accessed hosts.")
+
+(defvar pcomplete--host-name-cache-timestamp nil
+  "A timestamp of when the hosts file was read.")
+
+(defun pcomplete-read-hosts-file (filename)
+  "Read in the hosts from FILENAME, default `pcomplete-hosts-file'."
+  (let (hosts)
+    (with-temp-buffer
+      (insert-file-contents (or filename pcomplete-hosts-file))
+      (goto-char (point-min))
+      (while (re-search-forward
+              ;; "^ \t\\([^# \t\n]+\\)[ \t]+\\([^ \t\n]+\\)\\([ \t]*\\([^ \t\n]+\\)\\)?"
+              "^[ \t]*\\([^# \t\n]+\\)[ \t]+\\([^ \t\n].+\\)" nil t)
+        (push (cons (match-string 1)
+                    (split-string (match-string 2)))
+              hosts)))
+    (nreverse hosts)))
+
+(defun pcomplete-read-hosts (file result-var timestamp-var)
+  "Read the contents of /etc/hosts for host names."
+  (if (or (not (symbol-value result-var))
+          (not (symbol-value timestamp-var))
+          (time-less-p
+           (symbol-value timestamp-var)
+           (file-attribute-modification-time (file-attributes file))))
+      (progn
+        (set result-var (apply #'nconc (pcomplete-read-hosts-file file)))
+        (set timestamp-var (current-time))))
+  (symbol-value result-var))
+
+(defun pcomplete-read-host-names ()
+  "Read the contents of /etc/hosts for host names."
+  (if pcomplete-hosts-file
+      (pcomplete-read-hosts pcomplete-hosts-file 'pcomplete--host-name-cache
+                   'pcomplete--host-name-cache-timestamp)))
+
 ;; create a set of aliases which allow completion functions to be not
 ;; quite so verbose