From 2a9f33fa87d0825ef2f3a95f602e4f17bfb19b76 Mon Sep 17 00:00:00 2001
From: Jim Porter <jporterbugs@gmail.com>
Date: Tue, 10 Jan 2023 15:35:18 -0800
Subject: [PATCH] Add 'user-uid-for-file' to get the effective UID for remote
 files

In particular, this lets Eshell show a "#" root prompt sigil when the
user has sudo'ed via "cd /sudo::".

* lisp/simple.el (user-uid-for-file): New function.

* lisp/net/tramp.el (tramp-file-name-for-operation): Add
'user-uid-for-file'.
(tramp-handle-user-uid-for-file): New function.

* lisp/net/tramp-adb.el (tramp-adb-file-name-handler-alist):
* lisp/net/tramp-gvfs.el (tramp-gvfs-file-name-handler-alist):
* lisp/net/tramp-sh.el (tramp-sh-file-name-handler-alist):
* lisp/net/tramp-sudoedit.el (tramp-sudoedit-file-name-handler-alist):
Add 'user-uid-for-file'.

* lisp/net/tramp-archive.el (tramp-archive-file-name-handler-alist):
* lisp/net/tramp-crypt.el (tramp-crypt-file-name-handler-alist):
* lisp/net/tramp-rclone.el (tramp-rclone-file-name-handler-alist):
* lisp/net/tramp-smb.el (tramp-smb-file-name-handler-alist):
* lisp/net/tramp-sshfs.el (tramp-sshfs-file-name-handler-alist):
Add comment about 'user-uid-for-file'.

* lisp/eshell/em-prompt.el (eshell-prompt-function): Use
'user-uid-for-file'.

* doc/lispref/files.texi (Magic File Names): Mention
'user-uid-for-file'.

* etc/NEWS: Announce 'user-uid-for-file'.
---
 doc/lispref/files.texi     | 2 ++
 etc/NEWS                   | 4 ++++
 lisp/eshell/em-prompt.el   | 5 +++--
 lisp/net/tramp-adb.el      | 1 +
 lisp/net/tramp-archive.el  | 1 +
 lisp/net/tramp-crypt.el    | 1 +
 lisp/net/tramp-gvfs.el     | 1 +
 lisp/net/tramp-rclone.el   | 1 +
 lisp/net/tramp-sh.el       | 1 +
 lisp/net/tramp-smb.el      | 1 +
 lisp/net/tramp-sshfs.el    | 1 +
 lisp/net/tramp-sudoedit.el | 1 +
 lisp/net/tramp.el          | 6 ++++++
 lisp/simple.el             | 9 +++++++++
 14 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/doc/lispref/files.texi b/doc/lispref/files.texi
index 91643530f7f..6e42086ac66 100644
--- a/doc/lispref/files.texi
+++ b/doc/lispref/files.texi
@@ -3407,6 +3407,7 @@ Magic File Names
 @code{temporary-file-directory},
 @code{unhandled-file-name-directory},
 @code{unlock-file},
+@code{user-uid-for-file},
 @code{vc-registered},
 @code{verify-visited-file-modtime},@*
 @code{write-region}.
@@ -3468,6 +3469,7 @@ Magic File Names
 @code{temporary-file-directory},
 @code{unhandled-file-name-directory},
 @code{unlock-file},
+@code{user-uid-for-file},
 @code{vc-regis@discretionary{}{}{}tered},
 @code{verify-visited-file-modtime},
 @code{write-region}.
diff --git a/etc/NEWS b/etc/NEWS
index 690e9c3faa9..4d903d1faae 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -190,6 +190,10 @@ compared reliably at all.
 This warning can be suppressed using 'with-suppressed-warnings' with
 the warning name 'suspicious'.
 
+** New function 'user-uid-for-file'.
+This function is like 'user-uid', but is aware of file name handlers,
+so it will return the remote UID for remote files.
+
 
 * Changes in Emacs 30.1 on Non-Free Operating Systems
 
diff --git a/lisp/eshell/em-prompt.el b/lisp/eshell/em-prompt.el
index 575b5a595f1..bc6beaf3cde 100644
--- a/lisp/eshell/em-prompt.el
+++ b/lisp/eshell/em-prompt.el
@@ -49,8 +49,9 @@ eshell-prompt-load-hook
 
 (defcustom eshell-prompt-function
   (lambda ()
-    (concat (abbreviate-file-name (eshell/pwd))
-            (if (= (user-uid) 0) " # " " $ ")))
+    (let ((cwd (eshell/pwd)))
+      (concat (abbreviate-file-name cwd)
+              (if (= (user-uid-for-file cwd) 0) " # " " $ "))))
   "A function that returns the Eshell prompt string.
 Make sure to update `eshell-prompt-regexp' so that it will match your
 prompt."
diff --git a/lisp/net/tramp-adb.el b/lisp/net/tramp-adb.el
index 619d29bb4d6..8de47045b5e 100644
--- a/lisp/net/tramp-adb.el
+++ b/lisp/net/tramp-adb.el
@@ -188,6 +188,7 @@ tramp-adb-file-name-handler-alist
     (tramp-set-file-uid-gid . ignore)
     (unhandled-file-name-directory . ignore)
     (unlock-file . tramp-handle-unlock-file)
+    (user-uid-for-file . tramp-handle-user-uid-for-file)
     (vc-registered . ignore)
     (verify-visited-file-modtime . tramp-handle-verify-visited-file-modtime)
     (write-region . tramp-adb-handle-write-region))
diff --git a/lisp/net/tramp-archive.el b/lisp/net/tramp-archive.el
index a2add1ed73a..08e4a776cc3 100644
--- a/lisp/net/tramp-archive.el
+++ b/lisp/net/tramp-archive.el
@@ -300,6 +300,7 @@ tramp-archive-file-name-handler-alist
     (tramp-set-file-uid-gid . ignore)
     (unhandled-file-name-directory . ignore)
     (unlock-file . ignore)
+    ;; `user-uid-for-file' performed by default handler.
     (vc-registered . ignore)
     (verify-visited-file-modtime . tramp-handle-verify-visited-file-modtime)
     (write-region . tramp-archive-handle-not-implemented))
diff --git a/lisp/net/tramp-crypt.el b/lisp/net/tramp-crypt.el
index 61d1c529619..1192bc75762 100644
--- a/lisp/net/tramp-crypt.el
+++ b/lisp/net/tramp-crypt.el
@@ -239,6 +239,7 @@ tramp-crypt-file-name-handler-alist
     (tramp-set-file-uid-gid . tramp-crypt-handle-set-file-uid-gid)
     (unhandled-file-name-directory . ignore)
     (unlock-file . tramp-crypt-handle-unlock-file)
+    ;; `user-uid-for-file' performed by default handler.
     (vc-registered . ignore)
     (verify-visited-file-modtime . tramp-handle-verify-visited-file-modtime)
     (write-region . tramp-handle-write-region))
diff --git a/lisp/net/tramp-gvfs.el b/lisp/net/tramp-gvfs.el
index bb81b3eb66c..177a3fb7ebe 100644
--- a/lisp/net/tramp-gvfs.el
+++ b/lisp/net/tramp-gvfs.el
@@ -833,6 +833,7 @@ tramp-gvfs-file-name-handler-alist
     (tramp-set-file-uid-gid . tramp-gvfs-handle-set-file-uid-gid)
     (unhandled-file-name-directory . ignore)
     (unlock-file . tramp-handle-unlock-file)
+    (user-uid-for-file . tramp-handle-user-uid-for-file)
     (vc-registered . ignore)
     (verify-visited-file-modtime . tramp-handle-verify-visited-file-modtime)
     (write-region . tramp-handle-write-region))
diff --git a/lisp/net/tramp-rclone.el b/lisp/net/tramp-rclone.el
index 4018fa3aa29..3ac18a00278 100644
--- a/lisp/net/tramp-rclone.el
+++ b/lisp/net/tramp-rclone.el
@@ -153,6 +153,7 @@ tramp-rclone-file-name-handler-alist
     (tramp-set-file-uid-gid . ignore)
     (unhandled-file-name-directory . ignore)
     (unlock-file . tramp-handle-unlock-file)
+    ;; `user-uid-for-file' performed by default handler.
     (vc-registered . ignore)
     (verify-visited-file-modtime . tramp-handle-verify-visited-file-modtime)
     (write-region . tramp-handle-write-region))
diff --git a/lisp/net/tramp-sh.el b/lisp/net/tramp-sh.el
index fbdd40dd1d2..00d7324a4d0 100644
--- a/lisp/net/tramp-sh.el
+++ b/lisp/net/tramp-sh.el
@@ -1121,6 +1121,7 @@ tramp-sh-file-name-handler-alist
     (tramp-set-file-uid-gid . tramp-sh-handle-set-file-uid-gid)
     (unhandled-file-name-directory . ignore)
     (unlock-file . tramp-handle-unlock-file)
+    (user-uid-for-file . tramp-handle-user-uid-for-file)
     (vc-registered . tramp-sh-handle-vc-registered)
     (verify-visited-file-modtime . tramp-sh-handle-verify-visited-file-modtime)
     (write-region . tramp-sh-handle-write-region))
diff --git a/lisp/net/tramp-smb.el b/lisp/net/tramp-smb.el
index f31865d498d..10532c739c6 100644
--- a/lisp/net/tramp-smb.el
+++ b/lisp/net/tramp-smb.el
@@ -304,6 +304,7 @@ tramp-smb-file-name-handler-alist
     (tramp-set-file-uid-gid . ignore)
     (unhandled-file-name-directory . ignore)
     (unlock-file . tramp-handle-unlock-file)
+    ;; `user-uid-for-file' performed by default handler.
     (vc-registered . ignore)
     (verify-visited-file-modtime . tramp-handle-verify-visited-file-modtime)
     (write-region . tramp-smb-handle-write-region))
diff --git a/lisp/net/tramp-sshfs.el b/lisp/net/tramp-sshfs.el
index 27b2854e451..8118a8cfa25 100644
--- a/lisp/net/tramp-sshfs.el
+++ b/lisp/net/tramp-sshfs.el
@@ -159,6 +159,7 @@ tramp-sshfs-file-name-handler-alist
     (tramp-set-file-uid-gid . ignore)
     (unhandled-file-name-directory . ignore)
     (unlock-file . tramp-handle-unlock-file)
+    ;; `user-uid-for-file' performed by default handler.
     (vc-registered . ignore)
     (verify-visited-file-modtime . tramp-handle-verify-visited-file-modtime)
     (write-region . tramp-sshfs-handle-write-region))
diff --git a/lisp/net/tramp-sudoedit.el b/lisp/net/tramp-sudoedit.el
index c4e1d32f525..af7d5ba09ca 100644
--- a/lisp/net/tramp-sudoedit.el
+++ b/lisp/net/tramp-sudoedit.el
@@ -149,6 +149,7 @@ tramp-sudoedit-file-name-handler-alist
     (tramp-set-file-uid-gid . tramp-sudoedit-handle-set-file-uid-gid)
     (unhandled-file-name-directory . ignore)
     (unlock-file . tramp-handle-unlock-file)
+    (user-uid-for-file . tramp-handle-user-uid-for-file)
     (vc-registered . ignore)
     (verify-visited-file-modtime . tramp-handle-verify-visited-file-modtime)
     (write-region . tramp-handle-write-region))
diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index 4bf0fdefc0b..a93f4bda605 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -2589,6 +2589,8 @@ tramp-file-name-for-operation
 	      file-locked-p lock-file make-lock-file-name unlock-file
 	      ;; Emacs 29+ only.
 	      abbreviate-file-name
+	      ;; Emacs 30+ only.
+	      user-uid-for-file
 	      ;; Tramp internal magic file name function.
 	      tramp-set-file-uid-gid))
     (if (file-name-absolute-p (nth 0 args))
@@ -3690,6 +3692,10 @@ tramp-handle-abbreviate-file-name
 	 vec (concat "~" (substring filename (match-beginning 1))))
       (tramp-make-tramp-file-name (tramp-dissect-file-name filename)))))
 
+(defun tramp-handle-user-uid-for-file (filename)
+  "Like `user-uid' for Tramp files."
+  (tramp-get-remote-uid (tramp-dissect-file-name filename) 'integer))
+
 (defun tramp-handle-access-file (filename string)
   "Like `access-file' for Tramp files."
   (setq filename (file-truename filename))
diff --git a/lisp/simple.el b/lisp/simple.el
index 690968ca938..07dd3196a3e 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -4664,6 +4664,15 @@ shell-command--same-buffer-confirm
                      action))
       (user-error "Shell command in progress"))))
 
+(defun user-uid-for-file (filename)
+  "Return the effective uid for FILENAME.
+For local files, this is equivalent to `user-uid' (which see),
+but for remote files, this returns the effective uid for that
+remote connection."
+  (if-let ((handler (find-file-name-handler filename 'user-uid-for-file)))
+      (funcall handler 'user-uid-for-file filename)
+    (user-uid)))
+
 (defun max-mini-window-lines (&optional frame)
   "Compute maximum number of lines for echo area in FRAME.
 As defined by `max-mini-window-height'.  FRAME defaults to the
-- 
2.25.1