Remove Emacs 26 compatibility from Tramp

* doc/misc/tramp.texi (Remote processes): Don't mention Emacs version.
(Frequently Asked Questions): Adapt supported Emacs versions.

* doc/misc/trampver.texi:
* lisp/net/trampver.el: Change version to "2.7.0-pre".

* lisp/net/tramp-compat.el (tramp-compat-file-name-quoted-p)
(tramp-compat-file-name-quote, tramp-compat-file-name-unquote)
(tramp-compat-tramp-syntax, tramp-compat-exec-path)
(tramp-compat-time-equal-p, tramp-compat-flatten-tree)
(tramp-compat-progress-reporter-update)
(tramp-compat-ignore-error, tramp-compat-rx--transform-item)
(tramp-compat-rx--transform, tramp-compat-rx): Remove.

* lisp/net/tramp-adb.el:
* lisp/net/tramp-archive.el:
* lisp/net/tramp-cache.el:
* lisp/net/tramp-cmds.el:
* lisp/net/tramp-crypt.el:
* lisp/net/tramp-fuse.el:
* lisp/net/tramp-gvfs.el:
* lisp/net/tramp-integration.el:
* lisp/net/tramp-rclone.el:
* lisp/net/tramp-sh.el:
* lisp/net/tramp-smb.el:
* lisp/net/tramp-sshfs.el:
* lisp/net/tramp-sudoedit.el:
* lisp/net/tramp.el:
* lisp/net/trampver.el: Replace the removed `tramp-compat-*' items
by their real definition.  Don't use `tramp-compat-funcall' when
not needed.  Remove `with-no-warnings' and `ignore-errors' where
appropriate.

* lisp/net/tramp.el (tramp-file-name-for-operation): Rearrange list.
(tramp-handle-file-newer-than-file-p): Simplify.
(tramp-get-process-attributes): Don't check for existence of
`connection-local-criteria-for-default-directory'.
(tramp-handle-shell-command): Don't check for existence of
`shell-command-save-pos-or-erase', `async-shell-command-width' and
`shell-command-set-point-after-cmd'.
(tramp-handle-start-file-process): Call `make-process' directly.
(tramp-defined-time): New defsubst.
(tramp-get-local-gid): Don't check for existence of `group-name'.

* lisp/net/tramp-adb.el (tramp-adb-handle-set-file-times):
Use `tramp-defined-time'.
(tramp-adb-get-signal-strings): Don't bind `shell-file-name' and
`shell-command-switch'.

* lisp/net/tramp-archive.el (top, tramp-archive-file-name-handler):
Don't bind `max-specpdl-size' any longer.
(tramp-archive-autoload-file-name-regexp): Remove Emacs 26
specific code.
(top): Don't call `tramp-register-archive-autoload-file-name-handler'.

* lisp/net/tramp-gvfs.el (top): Don't bind `max-specpdl-size' any longer.
(tramp-gvfs-handle-set-file-times): Use `tramp-defined-time'.

* lisp/net/tramp-sh.el (tramp-sh-handle-set-file-times):
Use `tramp-defined-time'.

* test/lisp/net/tramp-archive-tests.el (tramp-archive--test-emacs27-p):
Remove.
(all):
* test/lisp/net/tramp-tests.el (all): Don't skip for Emacs 26.
Replace the removed `tramp-compat-*' items by their real
definition.  Don't use `tramp-compat-funcall' when not needed.
Remove `with-no-warnings' and `ignore-errors' where appropriate.
(with-connection-local-variables)
(shell-command-dont-erase-buffer): Don't declare.
(tramp-test10-write-region): Don't check for `make-empty-file'.
(tramp-test32-shell-command): Simplify.
(tramp-test34-explicit-shell-file-name): Don't protect
`explicit-shell-file-name' any longer.
(tramp--test-emacs27-p): Remove.

2 files changed, 157 insertions, 307 deletions

diff --git a/test/lisp/net/tramp-archive-tests.el b/test/lisp/net/tramp-archive-tests.el
index 96c1e78e37a..85766f95cda 100644
--- a/test/lisp/net/tramp-archive-tests.el
+++ b/test/lisp/net/tramp-archive-tests.el
@@ -121,12 +121,6 @@ the origin of the temporary TMPFILE, have no write permissions."
      (directory-files tmpfile 'full directory-files-no-dot-files-regexp))
     (delete-directory tmpfile)))
 
-(defun tramp-archive--test-emacs27-p ()
-  "Check for Emacs version >= 27.1.
-Some semantics has been changed for there, without new functions or
-variables, so we check the Emacs version directly."
-  (>= emacs-major-version 27))
-
 (ert-deftest tramp-archive-test00-availability ()
   "Test availability of archive file name functions."
   :expected-result (if tramp-archive-enabled :passed :failed)
@@ -615,16 +609,13 @@ This checks also `file-name-as-directory', `file-name-directory',
           (with-temp-buffer
             (insert-directory tramp-archive-test-archive nil)
             (goto-char (point-min))
-            (should
-             (looking-at-p
-              (tramp-compat-rx (literal tramp-archive-test-archive)))))
+            (should (looking-at-p (rx (literal tramp-archive-test-archive)))))
           (with-temp-buffer
             (insert-directory tramp-archive-test-archive "-al")
             (goto-char (point-min))
             (should
              (looking-at-p
-              (tramp-compat-rx
-               bol (+ nonl) blank (literal tramp-archive-test-archive) eol))))
+              (rx bol (+ nonl) blank (literal tramp-archive-test-archive) eol))))
           (with-temp-buffer
             (insert-directory
              (file-name-as-directory tramp-archive-test-archive)
@@ -877,12 +868,8 @@ This tests also `file-executable-p', `file-writable-p' and `set-file-modes'."
 (ert-deftest tramp-archive-test43-file-system-info ()
   "Check that `file-system-info' returns proper values."
   (skip-unless tramp-archive-enabled)
-  ;; Since Emacs 27.1.
-  (skip-unless (fboundp 'file-system-info))
 
-  ;; `file-system-info' exists since Emacs 27.  We don't want to see
-  ;; compiler warnings for older Emacsen.
-  (let ((fsi (with-no-warnings (file-system-info tramp-archive-test-archive))))
+  (let ((fsi (file-system-info tramp-archive-test-archive)))
     (skip-unless fsi)
     (should (and (consp fsi)
                  (= (length fsi) 3)
@@ -895,8 +882,6 @@ This tests also `file-executable-p', `file-writable-p' and `set-file-modes'."
   "Check that `tramp-archive' autoloads properly."
   :tags '(:expensive-test)
   (skip-unless tramp-archive-enabled)
-  ;; Autoloading tramp-archive works since Emacs 27.1.
-  (skip-unless (tramp-archive--test-emacs27-p))
 
   ;; tramp-archive is neither loaded at Emacs startup, nor when
   ;; loading a file like "/mock::foo" (which loads Tramp).
@@ -919,7 +904,7 @@ This tests also `file-executable-p', `file-writable-p' and `set-file-modes'."
         (dolist (file `("/mock::foo" ,(concat tramp-archive-test-archive "foo")))
           (should
            (string-match
-            (tramp-compat-rx
+            (rx
              "tramp-archive loaded: "
              (literal (symbol-name
                        (tramp-archive-file-name-p default-directory)))
@@ -942,8 +927,6 @@ This tests also `file-executable-p', `file-writable-p' and `set-file-modes'."
   "Check that `tramp-archive' is loaded lazily, only when needed."
   :tags '(:expensive-test)
   (skip-unless tramp-archive-enabled)
-  ;; Autoloading tramp-archive works since Emacs 27.1.
-  (skip-unless (tramp-archive--test-emacs27-p))
 
   ;; tramp-archive is neither loaded at Emacs startup, nor when
   ;; loading a file like "/foo.tar".  It is loaded only when
@@ -964,7 +947,7 @@ This tests also `file-executable-p', `file-writable-p' and `set-file-modes'."
     (dolist (tae '(t nil))
       (should
        (string-match
-        (tramp-compat-rx
+        (rx
          "tramp-archive loaded: nil" (+ ascii)
          "tramp-archive loaded: nil" (+ ascii)
          "tramp-archive loaded: " (literal (symbol-name tae)))
diff --git a/test/lisp/net/tramp-tests.el b/test/lisp/net/tramp-tests.el
index 6fb9fa1fae9..90f6fcd6b15 100644
--- a/test/lisp/net/tramp-tests.el
+++ b/test/lisp/net/tramp-tests.el
@@ -74,14 +74,10 @@
 (defvar tramp-remote-path)
 (defvar tramp-remote-process-environment)
 
-;; Needed for Emacs 26.
-(declare-function with-connection-local-variables "files-x")
 ;; Needed for Emacs 27.
 (defvar lock-file-name-transforms)
 (defvar process-file-return-signal-string)
 (defvar remote-file-name-inhibit-locks)
-(defvar shell-command-dont-erase-buffer)
-;; Needed for Emacs 28.
 (defvar dired-copy-dereference)
 
 ;; `ert-resource-file' was introduced in Emacs 28.1.
@@ -224,7 +220,7 @@ If LOCAL is non-nil, a local file name is returned.
 If QUOTED is non-nil, the local part of the file name is quoted.
 The temporary file is not created."
   (funcall
-   (if quoted #'tramp-compat-file-name-quote #'identity)
+   (if quoted #'file-name-quote #'identity)
    (expand-file-name
     (make-temp-name "tramp-test")
     (if local temporary-file-directory ert-remote-temporary-file-directory))))
@@ -2296,10 +2292,9 @@ This checks also `file-name-as-directory', `file-name-directory',
 
     ;; Check `directory-abbrev-alist' abbreviation.
     (let ((directory-abbrev-alist
-           `((,(tramp-compat-rx bos (literal home-dir) "/foo")
-              . ,(concat home-dir "/f"))
-             (,(tramp-compat-rx bos (literal remote-host) "/nowhere")
-              . ,(concat remote-host "/nw")))))
+           `((,(rx bos (literal home-dir) "/foo") . ,(concat home-dir "/f"))
+             (,(rx bos (literal remote-host) "/nowhere")
+              . ,(concat remote-host "/nw")))))
       (should (equal (abbreviate-file-name (concat home-dir "/foo/bar"))
                      (concat remote-host-nohop "~/f/bar")))
       (should (equal (abbreviate-file-name
@@ -2479,17 +2474,14 @@ This checks also `file-name-as-directory', `file-name-directory',
               (should (string-equal (buffer-string) "foo")))
 
             ;; Write empty string.  Used for creation of temporary files.
-            ;; Since Emacs 27.1.
-            (when (fboundp 'make-empty-file)
-              (with-no-warnings
-                (should-error
-                 (make-empty-file tmp-name)
-                 :type 'file-already-exists)
-                (delete-file tmp-name)
-                (make-empty-file tmp-name)
-                (with-temp-buffer
-                  (insert-file-contents tmp-name)
-                  (should (string-equal (buffer-string) "")))))
+            (should-error
+             (make-empty-file tmp-name)
+             :type 'file-already-exists)
+            (delete-file tmp-name)
+            (make-empty-file tmp-name)
+            (with-temp-buffer
+              (insert-file-contents tmp-name)
+              (should (string-equal (buffer-string) "")))
 
             ;; Write partly.
             (with-temp-buffer
@@ -2511,8 +2503,7 @@ This checks also `file-name-as-directory', `file-name-directory',
                      (string-match-p
                       (if (and (null noninteractive)
                                (or (eq visit t) (null visit) (stringp visit)))
-                          (tramp-compat-rx
-                           bol "Wrote " (literal tmp-name) "\n" eos)
+                          (rx bol "Wrote " (literal tmp-name) "\n" eos)
                         (rx bos))
                       tramp--test-messages))))))
 
@@ -2542,8 +2533,6 @@ This checks also `file-name-as-directory', `file-name-directory',
   "Check that `file-precious-flag' is respected with Tramp in use."
   (skip-unless (tramp--test-enabled))
   (skip-unless (tramp--test-sh-p))
-  ;; The bug is fixed in Emacs 27.1.
-  (skip-unless (tramp--test-emacs27-p))
 
   (let* ((tmp-name (tramp--test-make-temp-name))
          (inhibit-message t)
@@ -2626,10 +2615,7 @@ This checks also `file-name-as-directory', `file-name-directory',
   "Check `copy-file'."
   (skip-unless (tramp--test-enabled))
 
-  ;; `filename-non-special' has been fixed in Emacs 27.1, see Bug#29579.
-  (dolist (quoted
-           (if (and (tramp--test-expensive-test-p) (tramp--test-emacs27-p))
-               '(nil t) '(nil)))
+  (dolist (quoted (if (tramp--test-expensive-test-p) '(nil t) '(nil)))
     (let ((tmp-name1 (tramp--test-make-temp-name nil quoted))
           (tmp-name2 (tramp--test-make-temp-name nil quoted))
           (tmp-name3 (tramp--test-make-temp-name 'local quoted)))
@@ -2738,10 +2724,7 @@ This checks also `file-name-as-directory', `file-name-directory',
   "Check `rename-file'."
   (skip-unless (tramp--test-enabled))
 
-  ;; `filename-non-special' has been fixed in Emacs 27.1, see Bug#29579.
-  (dolist (quoted
-           (if (and (tramp--test-expensive-test-p) (tramp--test-emacs27-p))
-               '(nil t) '(nil)))
+  (dolist (quoted  (if (tramp--test-expensive-test-p) '(nil t) '(nil)))
     (let ((tmp-name1 (tramp--test-make-temp-name nil quoted))
           (tmp-name2 (tramp--test-make-temp-name nil quoted))
           (tmp-name3 (tramp--test-make-temp-name 'local quoted)))
@@ -2925,13 +2908,11 @@ This tests also `file-directory-p' and `file-accessible-directory-p'."
       (delete-directory tmp-name1 'recursive)
       (should-not (file-directory-p tmp-name1))
 
-      ;; Trashing directories works only since Emacs 27.1.  It doesn't
-      ;; work when `system-move-file-to-trash' is defined (on MS
-      ;; Windows and macOS), for encrypted remote directories and for
-      ;; ange-ftp.
+      ;; Trashing directories doesn't work when
+      ;; `system-move-file-to-trash' is defined (on MS Windows and
+      ;; macOS), for encrypted remote directories and for ange-ftp.
       (when (and (not (fboundp 'system-move-file-to-trash))
-                 (not (tramp--test-crypt-p)) (not (tramp--test-ftp-p))
-                 (tramp--test-emacs27-p))
+                 (not (tramp--test-crypt-p)) (not (tramp--test-ftp-p)))
         (let ((trash-directory (tramp--test-make-temp-name 'local quoted))
               (delete-by-moving-to-trash t))
           (make-directory trash-directory)
@@ -3200,9 +3181,6 @@ This tests also `file-directory-p' and `file-accessible-directory-p'."
   ;; (this is performed by `dired').  If FULL is nil, it shows just
   ;; one file.  So we refrain from testing.
   (skip-unless (not (tramp--test-ange-ftp-p)))
-  ;; `insert-directory' of encrypted remote directories works only
-  ;; since Emacs 27.1.
-  (skip-unless (or (not (tramp--test-crypt-p)) (tramp--test-emacs27-p)))
 
   (dolist (quoted (if (tramp--test-expensive-test-p) '(nil t) '(nil)))
     (let* ((tmp-name1
@@ -3220,26 +3198,23 @@ This tests also `file-directory-p' and `file-accessible-directory-p'."
             (with-temp-buffer
               (insert-directory tmp-name1 nil)
               (goto-char (point-min))
-              (should (looking-at-p (tramp-compat-rx (literal tmp-name1)))))
+              (should (looking-at-p (rx (literal tmp-name1)))))
             (with-temp-buffer
               (insert-directory (file-name-as-directory tmp-name1) nil)
               (goto-char (point-min))
               (should
-               (looking-at-p
-                (tramp-compat-rx (literal (file-name-as-directory tmp-name1))))))
+               (looking-at-p (rx (literal (file-name-as-directory tmp-name1))))))
             (with-temp-buffer
               (insert-directory tmp-name1 "-al")
               (goto-char (point-min))
               (should
-               (looking-at-p
-                (tramp-compat-rx bol (+ nonl) blank (literal tmp-name1) eol))))
+               (looking-at-p (rx bol (+ nonl) blank (literal tmp-name1) eol))))
             (with-temp-buffer
               (insert-directory (file-name-as-directory tmp-name1) "-al")
               (goto-char (point-min))
               (should
                (looking-at-p
-                (tramp-compat-rx
-                 bol (+ nonl) blank (literal tmp-name1) "/" eol))))
+                (rx bol (+ nonl) blank (literal tmp-name1) "/" eol))))
             (with-temp-buffer
               (insert-directory
                (file-name-as-directory tmp-name1) "-al" nil 'full-directory-p)
@@ -3300,7 +3275,7 @@ This tests also `file-directory-p' and `file-accessible-directory-p'."
            (tmp-name4 (expand-file-name "bar" tmp-name2))
            (ert-remote-temporary-file-directory
             (funcall
-             (if quoted #'tramp-compat-file-name-quote #'identity)
+             (if quoted #'file-name-quote #'identity)
              ert-remote-temporary-file-directory))
            buffer)
       (unwind-protect
@@ -3323,14 +3298,14 @@ This tests also `file-directory-p' and `file-accessible-directory-p'."
               (goto-char (point-min))
               (should
                (re-search-forward
-                (tramp-compat-rx
+                (rx
                  (literal
                   (file-relative-name
                    tmp-name1 ert-remote-temporary-file-directory)))))
               (goto-char (point-min))
               (should
                (re-search-forward
-                (tramp-compat-rx
+                (rx
                  (literal
                   (file-relative-name
                    tmp-name2 ert-remote-temporary-file-directory))))))
@@ -3345,14 +3320,14 @@ This tests also `file-directory-p' and `file-accessible-directory-p'."
               (goto-char (point-min))
               (should
                (re-search-forward
-                (tramp-compat-rx
+                (rx
                  (literal
                   (file-relative-name
                    tmp-name3 ert-remote-temporary-file-directory)))))
               (goto-char (point-min))
               (should
                (re-search-forward
-                (tramp-compat-rx
+                (rx
                  (literal
                   (file-relative-name
                    tmp-name4
@@ -3375,14 +3350,14 @@ This tests also `file-directory-p' and `file-accessible-directory-p'."
               (goto-char (point-min))
               (should
                (re-search-forward
-                (tramp-compat-rx
+                (rx
                  (literal
                   (file-relative-name
                    tmp-name3 ert-remote-temporary-file-directory)))))
               (goto-char (point-min))
               (should
                (re-search-forward
-                (tramp-compat-rx
+                (rx
                  (literal
                   (file-relative-name
                    tmp-name4
@@ -3552,7 +3527,7 @@ This tests also `access-file', `file-readable-p',
               (should
                (string-equal
                 (funcall
-                 (if quoted #'tramp-compat-file-name-quote #'identity)
+                 (if quoted #'file-name-quote #'identity)
                  (file-attribute-type attr))
                 (file-remote-p (file-truename tmp-name1) 'localname)))
               (delete-file tmp-name2))
@@ -3616,9 +3591,6 @@ This tests also `access-file', `file-readable-p',
                (cons '(nil "perl" nil)
                      tramp-connection-properties)))
          (progn
-           ;; `ert-test-result-duration' exists since Emacs 27.  It
-           ;; doesn't hurt to call it unconditionally, because
-           ;; `skip-unless' hides the error.
            (skip-unless (< (ert-test-result-duration result) 300))
            (funcall (ert-test-body ert-test)))
        (ert-skip (format "Test `%s' must run before" ',test)))))
@@ -3647,9 +3619,6 @@ This tests also `access-file', `file-readable-p',
                   (nil "id" nil))
                 tramp-connection-properties)))
          (progn
-           ;; `ert-test-result-duration' exists since Emacs 27.  It
-           ;; doesn't hurt to call it unconditionally, because
-           ;; `skip-unless' hides the error.
            (skip-unless (< (ert-test-result-duration result) 300))
            (funcall (ert-test-body ert-test)))
        (ert-skip (format "Test `%s' must run before" ',test)))))
@@ -3676,9 +3645,6 @@ This tests also `access-file', `file-readable-p',
                   (nil "readlink" nil))
                 tramp-connection-properties)))
          (progn
-           ;; `ert-test-result-duration' exists since Emacs 27.  It
-           ;; doesn't hurt to call it unconditionally, because
-           ;; `skip-unless' hides the error.
            (skip-unless (< (ert-test-result-duration result) 300))
            (funcall (ert-test-body ert-test)))
        (ert-skip (format "Test `%s' must run before" ',test)))))
@@ -3714,9 +3680,9 @@ They might differ only in time attributes or directory size."
     ;; few seconds).  We use a test start time minus 10 seconds, in
     ;; order to compensate a possible timestamp resolution higher than
     ;; a second on the remote machine.
-    (when (or (tramp-compat-time-equal-p
+    (when (or (time-equal-p
                (file-attribute-modification-time attr1) tramp-time-dont-know)
-              (tramp-compat-time-equal-p
+              (time-equal-p
                (file-attribute-modification-time attr2) tramp-time-dont-know))
       (setcar (nthcdr 5 attr1) tramp-time-dont-know)
       (setcar (nthcdr 5 attr2) tramp-time-dont-know))
@@ -3727,9 +3693,9 @@ They might differ only in time attributes or directory size."
              (float-time (file-attribute-modification-time attr2)))
       (setcar (nthcdr 5 attr2) tramp-time-dont-know))
     ;; Status change time.  Ditto.
-    (when (or (tramp-compat-time-equal-p
+    (when (or (time-equal-p
                (file-attribute-status-change-time attr1) tramp-time-dont-know)
-              (tramp-compat-time-equal-p
+              (time-equal-p
                (file-attribute-status-change-time attr2) tramp-time-dont-know))
       (setcar (nthcdr 6 attr1) tramp-time-dont-know)
       (setcar (nthcdr 6 attr2) tramp-time-dont-know))
@@ -3868,7 +3834,7 @@ This tests also `file-executable-p', `file-writable-p' and `set-file-modes'."
               (should
                (string-equal
                 (funcall
-                 (if quoted #'tramp-compat-file-name-unquote #'identity)
+                 (if quoted #'file-name-unquote #'identity)
                  (file-remote-p tmp-name1 'localname))
                 (file-symlink-p tmp-name2)))
               ;; Both report the modes of `tmp-name1'.
@@ -3938,7 +3904,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
             (should
              (string-equal
               (funcall
-               (if quoted #'tramp-compat-file-name-unquote #'identity)
+               (if quoted #'file-name-unquote #'identity)
                (file-remote-p tmp-name1 'localname))
               (file-symlink-p tmp-name2)))
             (when (tramp--test-expensive-test-p)
@@ -3956,14 +3922,14 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
               (should
                (string-equal
                 (funcall
-                 (if quoted #'tramp-compat-file-name-unquote #'identity)
+                 (if quoted #'file-name-unquote #'identity)
                  (file-remote-p tmp-name1 'localname))
                 (file-symlink-p tmp-name2))))
             (make-symbolic-link tmp-name1 tmp-name2 'ok-if-already-exists)
             (should
              (string-equal
               (funcall
-               (if quoted #'tramp-compat-file-name-unquote #'identity)
+               (if quoted #'file-name-unquote #'identity)
                (file-remote-p tmp-name1 'localname))
               (file-symlink-p tmp-name2)))
             ;; If we use the local part of `tmp-name1', it shall still work.
@@ -3973,7 +3939,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
             (should
              (string-equal
               (funcall
-               (if quoted #'tramp-compat-file-name-unquote #'identity)
+               (if quoted #'file-name-unquote #'identity)
                (file-remote-p tmp-name1 'localname))
               (file-symlink-p tmp-name2)))
             ;; `tmp-name3' is a local file name.  Therefore, the link
@@ -3993,7 +3959,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
             (should
              (string-equal
               (funcall
-               (if quoted #'tramp-compat-file-name-unquote #'identity)
+               (if quoted #'file-name-unquote #'identity)
                (file-remote-p tmp-name1 'localname))
               (file-symlink-p tmp-name5)))
             ;; Check, that files in symlinked directories still work.
@@ -4082,15 +4048,13 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
                        "/[penguin/motd]" "/penguin:motd:")))
               (delete-file tmp-name2)
               (make-symbolic-link
-               (funcall
-                (if quoted #'tramp-compat-file-name-unquote #'identity) penguin)
+               (funcall (if quoted #'file-name-unquote #'identity) penguin)
                tmp-name2)
               (should (file-symlink-p tmp-name2))
               (should
                (string-equal
                 (file-truename tmp-name2)
-                (tramp-compat-file-name-quote
-                 (concat (file-remote-p tmp-name2) penguin)))))
+                (file-name-quote (concat (file-remote-p tmp-name2) penguin)))))
             ;; `tmp-name3' is a local file name.
             ;; `make-symbolic-link' might not be permitted on w32 systems.
             (unless (tramp--test-windows-nt-p)
@@ -4102,7 +4066,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
               (should
                (string-equal
                 (file-truename tmp-name1)
-                (tramp-compat-file-name-unquote (file-truename tmp-name3))))))
+                (file-name-unquote (file-truename tmp-name3))))))
 
         ;; Cleanup.
         (ignore-errors
@@ -4175,7 +4139,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
       (let* ((dir1
               (directory-file-name
                (funcall
-                (if quoted #'tramp-compat-file-name-quote #'identity)
+                (if quoted #'file-name-quote #'identity)
                 ert-remote-temporary-file-directory)))
              (dir2 (file-name-as-directory dir1)))
         (should (string-equal (file-truename dir1) (expand-file-name dir1)))
@@ -4204,12 +4168,12 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
             (skip-unless (set-file-times tmp-name1 (seconds-to-time 60)))
             ;; Dumb remote shells without perl(1) or stat(1) are not
             ;; able to return the date correctly.  They say "don't know".
-            (unless (tramp-compat-time-equal-p
+            (unless (time-equal-p
                      (file-attribute-modification-time
                       (file-attributes tmp-name1))
                      tramp-time-dont-know)
               (should
-               (tramp-compat-time-equal-p
+               (time-equal-p
                 (file-attribute-modification-time (file-attributes tmp-name1))
                 (seconds-to-time 60)))
               ;; Setting the time for not existing files shall fail.
@@ -4228,7 +4192,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
                 (with-no-warnings
                   (set-file-times tmp-name1 (seconds-to-time 60) 'nofollow)
                   (should
-                   (tramp-compat-time-equal-p
+                   (time-equal-p
                     (file-attribute-modification-time
                      (file-attributes tmp-name1))
                     (seconds-to-time 60)))))))
@@ -4274,10 +4238,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
   (skip-unless (file-acl ert-remote-temporary-file-directory))
   (skip-unless (not (tramp--test-crypt-p)))
 
-  ;; `filename-non-special' has been fixed in Emacs 27.1, see Bug#29579.
-  (dolist (quoted
-           (if (and (tramp--test-expensive-test-p) (tramp--test-emacs27-p))
-               '(nil t) '(nil)))
+  (dolist (quoted (if (tramp--test-expensive-test-p) '(nil t) '(nil)))
     (let ((tmp-name1 (tramp--test-make-temp-name nil quoted))
           (tmp-name2 (tramp--test-make-temp-name nil quoted))
           (tmp-name3 (tramp--test-make-temp-name 'local quoted)))
@@ -4354,10 +4315,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
                '(nil nil nil nil))))
   (skip-unless (not (tramp--test-crypt-p)))
 
-  ;; `filename-non-special' has been fixed in Emacs 27.1, see Bug#29579.
-  (dolist (quoted
-           (if (and (tramp--test-expensive-test-p) (tramp--test-emacs27-p))
-               '(nil t) '(nil)))
+  (dolist (quoted (if (tramp--test-expensive-test-p) '(nil t) '(nil)))
     (let ((tmp-name1 (tramp--test-make-temp-name nil quoted))
           (tmp-name2 (tramp--test-make-temp-name nil quoted))
           (tmp-name3 (tramp--test-make-temp-name 'local quoted)))
@@ -4862,9 +4820,10 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
       (unless (tramp--test-sshfs-p)
         (unwind-protect
             (with-temp-buffer
-            (setq command '("cat")
-                  proc
-                  (apply #'start-file-process "test4" (current-buffer) command))
+              (setq command '("cat")
+                    proc
+                    (apply
+                     #'start-file-process "test4" (current-buffer) command))
               (should (processp proc))
               (should (equal (process-status proc) 'run))
               (should (equal (process-get proc 'remote-command) command))
@@ -4884,12 +4843,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
       ;; Process connection type.
       (when (and (tramp--test-sh-p)
                  (not (tramp-direct-async-process-p))
-                 ;; `executable-find' has changed the number of
-                 ;; parameters in Emacs 27.1, so we use `apply' for
-                 ;; older Emacsen.
-                 (ignore-errors
-                   (with-no-warnings
-                     (apply #'executable-find '("hexdump" remote)))))
+                 (executable-find "hexdump" 'remote))
         (dolist (process-connection-type '(nil pipe t pty))
           (unwind-protect
               (with-temp-buffer
@@ -4946,33 +4900,29 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
   "Define ert test `TEST-direct-async' for direct async processes.
 If UNSTABLE is non-nil, the test is tagged as `:unstable'."
   (declare (indent 1))
-  ;; `make-process' supports file name handlers since Emacs 27.  We
-  ;; cannot use `tramp--test-always' during compilation of the macro.
-  (when (let ((file-name-handler-alist '(("" . (lambda (&rest _) t)))))
-          (ignore-errors (make-process :file-handler t)))
-    `(ert-deftest ,(intern (concat (symbol-name test) "-direct-async")) ()
-       ;; This is the docstring.  However, it must be expanded to a
-       ;; string inside the macro.  No idea.
-       ;; (concat (ert-test-documentation (get ',test 'ert--test))
-       ;;         "\nUse direct async process.")
-       :tags (append '(:expensive-test :tramp-asynchronous-processes)
-                     (and ,unstable '(:unstable)))
-       (skip-unless (tramp--test-enabled))
-       (let ((default-directory ert-remote-temporary-file-directory)
-             (ert-test (ert-get-test ',test))
-             (tramp-connection-properties
-              (cons '(nil "direct-async-process" t)
-                    tramp-connection-properties)))
-         (skip-unless (tramp-direct-async-process-p))
-         ;; We do expect an established connection already,
-         ;; `file-truename' does it by side-effect.  Suppress
-         ;; `tramp--test-enabled', in order to keep the connection.
-         ;; Suppress "Process ... finished" messages.
-         (cl-letf (((symbol-function #'tramp--test-enabled) #'tramp--test-always)
-                   ((symbol-function #'internal-default-process-sentinel)
-                    #'ignore))
-           (file-truename ert-remote-temporary-file-directory)
-           (funcall (ert-test-body ert-test)))))))
+  `(ert-deftest ,(intern (concat (symbol-name test) "-direct-async")) ()
+     ;; This is the docstring.  However, it must be expanded to a
+     ;; string inside the macro.  No idea.
+     ;; (concat (ert-test-documentation (get ',test 'ert--test))
+     ;;         "\nUse direct async process.")
+     :tags (append '(:expensive-test :tramp-asynchronous-processes)
+                   (and ,unstable '(:unstable)))
+     (skip-unless (tramp--test-enabled))
+     (let ((default-directory ert-remote-temporary-file-directory)
+           (ert-test (ert-get-test ',test))
+           (tramp-connection-properties
+            (cons '(nil "direct-async-process" t)
+                  tramp-connection-properties)))
+       (skip-unless (tramp-direct-async-process-p))
+       ;; We do expect an established connection already,
+       ;; `file-truename' does it by side-effect.  Suppress
+       ;; `tramp--test-enabled', in order to keep the connection.
+       ;; Suppress "Process ... finished" messages.
+       (cl-letf (((symbol-function #'tramp--test-enabled) #'tramp--test-always)
+                 ((symbol-function #'internal-default-process-sentinel)
+                  #'ignore))
+         (file-truename ert-remote-temporary-file-directory)
+         (funcall (ert-test-body ert-test))))))
 
 (tramp--test-deftest-direct-async-process tramp-test29-start-file-process)
 
@@ -4983,24 +4933,21 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
                      '(:unstable)))
   (skip-unless (tramp--test-enabled))
   (skip-unless (tramp--test-supports-processes-p))
-  ;; `make-process' supports file name handlers since Emacs 27.
-  (skip-unless (tramp--test-emacs27-p))
 
   (dolist (quoted (if (tramp--test-expensive-test-p) '(nil t) '(nil)))
     (let ((default-directory ert-remote-temporary-file-directory)
           (tmp-name (tramp--test-make-temp-name nil quoted))
           kill-buffer-query-functions command proc)
-      (with-no-warnings (should-not (make-process)))
+      (should-not (make-process))
 
       ;; Simple process.
       (unwind-protect
           (with-temp-buffer
             (setq command '("cat")
                   proc
-                  (with-no-warnings
-                    (make-process
-                     :name "test1" :buffer (current-buffer) :command command
-                     :file-handler t)))
+                  (make-process
+                   :name "test1" :buffer (current-buffer) :command command
+                   :file-handler t))
             (should (processp proc))
             (should (equal (process-status proc) 'run))
             (should (equal (process-get proc 'remote-command) command))
@@ -5022,10 +4969,9 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
             (should (file-exists-p tmp-name))
             (setq command `("cat" ,(file-name-nondirectory tmp-name))
                   proc
-                  (with-no-warnings
-                    (make-process
-                     :name "test2" :buffer (current-buffer) :command command
-                     :file-handler t)))
+                  (make-process
+                   :name "test2" :buffer (current-buffer) :command command
+                   :file-handler t))
             (should (processp proc))
             (should (equal (process-get proc 'remote-command) command))
             ;; Read output.
@@ -5044,13 +4990,12 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
           (with-temp-buffer
             (setq command '("cat")
                   proc
-                  (with-no-warnings
-                    (make-process
-                     :name "test3" :buffer (current-buffer) :command command
-                     :filter
-                     (lambda (p s)
-                       (with-current-buffer (process-buffer p) (insert s)))
-                     :file-handler t)))
+                  (make-process
+                   :name "test3" :buffer (current-buffer) :command command
+                   :filter
+                   (lambda (p s)
+                     (with-current-buffer (process-buffer p) (insert s)))
+                   :file-handler t))
             (should (processp proc))
             (should (equal (process-status proc) 'run))
             (should (equal (process-get proc 'remote-command) command))
@@ -5071,11 +5016,9 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
             (with-temp-buffer
               (setq command '("cat")
                     proc
-                    (with-no-warnings
-                      (make-process
-                       :name "test4" :buffer (current-buffer) :command command
-                       :filter t
-                       :file-handler t)))
+                    (make-process
+                     :name "test4" :buffer (current-buffer) :command command
+                     :filter t :file-handler t))
               (should (processp proc))
               (should (equal (process-status proc) 'run))
               (should (equal (process-get proc 'remote-command) command))
@@ -5096,13 +5039,12 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
           (with-temp-buffer
             (setq command '("cat")
                   proc
-                  (with-no-warnings
-                    (make-process
-                     :name "test5" :buffer (current-buffer) :command command
-                     :sentinel
-                     (lambda (p s)
-                       (with-current-buffer (process-buffer p) (insert s)))
-                     :file-handler t)))
+                  (make-process
+                   :name "test5" :buffer (current-buffer) :command command
+                   :sentinel
+                   (lambda (p s)
+                     (with-current-buffer (process-buffer p) (insert s)))
+                   :file-handler t))
             (should (processp proc))
             (should (equal (process-status proc) 'run))
             (should (equal (process-get proc 'remote-command) command))
@@ -5128,11 +5070,9 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
               (with-temp-buffer
                 (setq command '("cat" "/does-not-exist")
                       proc
-                      (with-no-warnings
-                        (make-process
-                         :name "test6" :buffer (current-buffer) :command  command
-                         :stderr stderr
-                         :file-handler t)))
+                      (make-process
+                       :name "test6" :buffer (current-buffer) :command  command
+                       :stderr stderr :file-handler t))
                 (should (processp proc))
                 (should (equal (process-get proc 'remote-command) command))
                 ;; Read output.
@@ -5161,11 +5101,9 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
             (with-temp-buffer
               (setq command '("cat" "/does-not-exist")
                     proc
-                    (with-no-warnings
-                      (make-process
-                       :name "test7" :buffer (current-buffer) :command command
-                       :stderr tmp-name
-                       :file-handler t)))
+                    (make-process
+                     :name "test7" :buffer (current-buffer) :command command
+                     :stderr tmp-name :file-handler t))
               (should (processp proc))
               (should (equal (process-get proc 'remote-command) command))
               ;; Read stderr.
@@ -5186,12 +5124,7 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
       ;; Process connection type.
       (when (and (tramp--test-sh-p)
                  (not (tramp-direct-async-process-p))
-                 ;; `executable-find' has changed the number of
-                 ;; parameters in Emacs 27.1, so we use `apply' for
-                 ;; older Emacsen.
-                 (ignore-errors
-                   (with-no-warnings
-                     (apply #'executable-find '("hexdump" remote)))))
+                 (executable-find "hexdump" 'remote))
         (dolist (connection-type '(nil pipe t pty))
           ;; `process-connection-type' is taken when
           ;; `:connection-type' is nil.
@@ -5201,15 +5134,14 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
                 (with-temp-buffer
                   (setq command '("hexdump" "-v" "-e" "/1 \"%02X\n\"")
                         proc
-                        (with-no-warnings
-                          (make-process
-                           :name
-                           (format "test8-%s-%s"
-                                   connection-type process-connection-type)
-                           :buffer (current-buffer)
-                           :connection-type connection-type
-                           :command command
-                           :file-handler t)))
+                        (make-process
+                         :name
+                         (format "test8-%s-%s"
+                                 connection-type process-connection-type)
+                         :buffer (current-buffer)
+                         :connection-type connection-type
+                         :command command
+                         :file-handler t))
                   (should (processp proc))
                   (should (equal (process-status proc) 'run))
                   (should (equal (process-get proc 'remote-command) command))
@@ -5245,8 +5177,6 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
   (skip-unless (tramp--test-sh-p))
   (skip-unless (not (tramp--test-windows-nt-p)))
   (skip-unless (not (tramp--test-crypt-p)))
-  ;; Since Emacs 27.1.
-  (skip-unless (macrop 'with-connection-local-variables))
 
   ;; We must use `file-truename' for the temporary directory, in
   ;; order to establish the connection prior running an asynchronous
@@ -5288,8 +5218,6 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
   (skip-unless (tramp--test-sh-p))
   (skip-unless (not (tramp--test-windows-nt-p)))
   (skip-unless (not (tramp--test-crypt-p)))
-  ;; Since Emacs 27.1.
-  (skip-unless (macrop 'with-connection-local-variables))
   ;; Since Emacs 29.1.
   (skip-unless (boundp 'signal-process-functions))
 
@@ -5416,11 +5344,9 @@ If UNSTABLE is non-nil, the test is tagged as `:unstable'."
 INPUT, if non-nil, is a string sent to the process."
   (let ((proc (async-shell-command command output-buffer error-buffer))
         (delete-exited-processes t))
-    ;; Since Emacs 27.1.
-    (when (macrop 'with-connection-local-variables)
-      (should (equal (process-get proc 'remote-command)
-                     (with-connection-local-variables
-                      `(,shell-file-name ,shell-command-switch ,command)))))
+    (should (equal (process-get proc 'remote-command)
+                   (with-connection-local-variables
+                    `(,shell-file-name ,shell-command-switch ,command))))
     (cl-letf (((symbol-function #'shell-command-sentinel) #'ignore))
       (when (stringp input)
         (process-send-string proc input))
@@ -5441,10 +5367,6 @@ INPUT, if non-nil, is a string sent to the process."
   :tags '(:expensive-test)
   (skip-unless (tramp--test-enabled))
   (skip-unless (tramp--test-supports-processes-p))
-  ;; Prior Emacs 27, `shell-file-name' was hard coded as "/bin/sh" for
-  ;; remote processes in Emacs.  That doesn't work for tramp-adb.el.
-  (when (tramp--test-adb-p)
-    (skip-unless (tramp--test-emacs27-p)))
 
   (dolist (quoted (if (tramp--test-expensive-test-p) '(nil t) '(nil)))
     (let ((tmp-name (tramp--test-make-temp-name nil quoted))
@@ -5512,7 +5434,7 @@ INPUT, if non-nil, is a string sent to the process."
               (should
                (string-match-p
                 ;; Some shells echo, for example the "adb" or "docker" methods.
-                (tramp-compat-rx
+                (rx
                  bos (** 1 2 (literal (file-name-nondirectory tmp-name)) "\n")
                  eos)
                 (buffer-string))))
@@ -5520,10 +5442,8 @@ INPUT, if non-nil, is a string sent to the process."
           ;; Cleanup.
           (ignore-errors (delete-file tmp-name))))))
 
-  ;; Test `async-shell-command-width'.  It exists since Emacs 26.1,
-  ;; but seems to work since Emacs 27.1 only.
-  (when (and (tramp--test-asynchronous-processes-p)
-             (tramp--test-sh-p) (tramp--test-emacs27-p))
+  ;; Test `async-shell-command-width'.
+  (when (and (tramp--test-asynchronous-processes-p) (tramp--test-sh-p))
     (let* ((async-shell-command-width 1024)
            (default-directory ert-remote-temporary-file-directory)
            (cols (ignore-errors
@@ -5543,8 +5463,6 @@ INPUT, if non-nil, is a string sent to the process."
   (skip-unless (tramp--test-enabled))
   (skip-unless nil)
   (skip-unless (tramp--test-supports-processes-p))
-  ;; Prior Emacs 27, `shell-command-dont-erase-buffer' wasn't working properly.
-  (skip-unless (tramp--test-emacs27-p))
 
   ;; (message "   s-c-d-e-b current-buffer buffer-string point")
   ;; (message "===============================================")
@@ -5719,8 +5637,7 @@ INPUT, if non-nil, is a string sent to the process."
         ;; Variable is set.
         (should
          (string-match-p
-          (tramp-compat-rx (literal envvar))
-          (funcall this-shell-command-to-string "set"))))
+          (rx (literal envvar)) (funcall this-shell-command-to-string "set"))))
 
       (unless (tramp-direct-async-process-p)
         ;; We force a reconnect, in order to have a clean environment.
@@ -5746,7 +5663,7 @@ INPUT, if non-nil, is a string sent to the process."
             ;; Variable is unset.
             (should-not
              (string-match-p
-              (tramp-compat-rx (literal envvar))
+              (rx (literal envvar))
               ;; We must remove PS1, the output is truncated otherwise.
               ;; We must suppress "_=VAR...".
               (funcall
@@ -5791,13 +5708,10 @@ INPUT, if non-nil, is a string sent to the process."
     (dolist (dir '("/mock:localhost#11111:" "/mock:localhost#22222:"))
       (tramp-cleanup-connection (tramp-dissect-file-name dir)))))
 
-;; Connection-local variables are enabled per default since Emacs 27.1.
 (ert-deftest tramp-test34-connection-local-variables ()
   "Check that connection-local variables are enabled."
   :tags '(:expensive-test)
   (skip-unless (tramp--test-enabled))
-  ;; Since Emacs 27.1.
-  (skip-unless (macrop 'with-connection-local-variables))
 
   (let* ((default-directory ert-remote-temporary-file-directory)
          (tmp-name1 (tramp--test-make-temp-name))
@@ -5861,19 +5775,12 @@ INPUT, if non-nil, is a string sent to the process."
   :tags '(:expensive-test :tramp-asynchronous-processes)
   (skip-unless (tramp--test-enabled))
   (skip-unless (tramp--test-supports-processes-p))
-  ;; Prior Emacs 27, `shell-file-name' was hard coded as "/bin/sh" for
-  ;; remote processes in Emacs.  That doesn't work for tramp-adb.el.
-  (when (tramp--test-adb-p)
-    (skip-unless (tramp--test-emacs27-p)))
 
   (let ((default-directory ert-remote-temporary-file-directory)
         explicit-shell-file-name kill-buffer-query-functions
         connection-local-profile-alist connection-local-criteria-alist)
     (unwind-protect
         (progn
-          ;; `shell-mode' would ruin our test, because it deletes all
-          ;; buffer local variables.  Not needed in Emacs 27.1.
-          (put 'explicit-shell-file-name 'permanent-local t)
           (connection-local-set-profile-variables
            'remote-sh
            `((explicit-shell-file-name . ,(tramp--test-shell-file-name))
@@ -5904,29 +5811,24 @@ INPUT, if non-nil, is a string sent to the process."
       (put 'explicit-shell-file-name 'permanent-local nil)
       (kill-buffer "*shell*"))))
 
-;; `exec-path' was introduced in Emacs 27.1.  `executable-find' has
-;; changed the number of parameters, so we use `apply' for older
-;; Emacsen.
 (ert-deftest tramp-test35-exec-path ()
   "Check `exec-path' and `executable-find'."
   (skip-unless (tramp--test-enabled))
   (skip-unless (tramp--test-supports-processes-p))
   (skip-unless (tramp--test-supports-set-file-modes-p))
-  ;; Since Emacs 27.1.
-  (skip-unless (fboundp 'exec-path))
 
   (let ((tmp-name (tramp--test-make-temp-name))
         (default-directory ert-remote-temporary-file-directory))
     (unwind-protect
         (progn
-          (should (consp (with-no-warnings (exec-path))))
+          (should (consp (exec-path)))
           ;; Last element is the `exec-directory'.
           (should
            (string-equal
-            (car (last (with-no-warnings (exec-path))))
+            (car (last (exec-path)))
             (file-remote-p default-directory 'localname)))
           ;; The shell "sh" shall always exist.
-          (should (apply #'executable-find '("sh" remote)))
+          (should (executable-find "sh" 'remote))
           ;; Since the last element in `exec-path' is the current
           ;; directory, an executable file in that directory will be
           ;; found.
@@ -5937,32 +5839,25 @@ INPUT, if non-nil, is a string sent to the process."
           (should (file-executable-p tmp-name))
           (should
            (string-equal
-            (apply
-             #'executable-find `(,(file-name-nondirectory tmp-name) remote))
+            (executable-find (file-name-nondirectory tmp-name) 'remote)
             (file-remote-p tmp-name 'localname)))
           (should-not
-           (apply
-            #'executable-find
-            `(,(concat (file-name-nondirectory tmp-name) "foo") remote))))
+           (executable-find
+            (concat (file-name-nondirectory tmp-name) "foo") 'remote)))
 
       ;; Cleanup.
       (ignore-errors (delete-file tmp-name)))))
 
 ;; This test is inspired by Bug#33781.
-;; `exec-path' was introduced in Emacs 27.1.  `executable-find' has
-;; changed the number of parameters, so we use `apply' for older
-;; Emacsen.
 (ert-deftest tramp-test35-remote-path ()
   "Check loooong `tramp-remote-path'."
   (skip-unless (tramp--test-enabled))
   (skip-unless (tramp--test-sh-p))
   (skip-unless (not (tramp--test-crypt-p)))
-  ;; Since Emacs 27.1.
-  (skip-unless (fboundp 'exec-path))
 
   (let* ((tmp-name (tramp--test-make-temp-name))
          (default-directory ert-remote-temporary-file-directory)
-         (orig-exec-path (with-no-warnings (exec-path)))
+         (orig-exec-path (exec-path))
          (tramp-remote-path tramp-remote-path)
          (orig-tramp-remote-path tramp-remote-path)
          path)
@@ -5972,14 +5867,13 @@ INPUT, if non-nil, is a string sent to the process."
           (setq tramp-remote-path
                 (cons (file-remote-p tmp-name 'localname) tramp-remote-path))
           (tramp-cleanup-connection tramp-test-vec 'keep-debug 'keep-password)
-          (should (equal (with-no-warnings (exec-path)) orig-exec-path))
+          (should (equal (exec-path) orig-exec-path))
           (setq tramp-remote-path orig-tramp-remote-path)
 
           ;; Double entries are removed.
           (setq tramp-remote-path (append '("/" "/") tramp-remote-path))
           (tramp-cleanup-connection tramp-test-vec 'keep-debug 'keep-password)
-          (should
-           (equal (with-no-warnings (exec-path)) (cons "/" orig-exec-path)))
+          (should (equal (exec-path) (cons "/" orig-exec-path)))
           (setq tramp-remote-path orig-tramp-remote-path)
 
           ;; We make a super long `tramp-remote-path'.
@@ -5997,7 +5891,7 @@ INPUT, if non-nil, is a string sent to the process."
                      `(,(file-remote-p dir 'localname))
                      (last orig-exec-path)))))
           (tramp-cleanup-connection tramp-test-vec 'keep-debug 'keep-password)
-          (should (equal (with-no-warnings (exec-path)) orig-exec-path))
+          (should (equal (exec-path) orig-exec-path))
           ;; Ignore trailing newline.
           (setq path (substring (shell-command-to-string "echo $PATH") nil -1))
           ;; The shell doesn't handle such long strings.
@@ -6009,7 +5903,7 @@ INPUT, if non-nil, is a string sent to the process."
              (string-equal
               path (mapconcat #'identity (butlast orig-exec-path) ":"))))
           ;; The shell "sh" shall always exist.
-          (should (apply #'executable-find '("sh" remote))))
+          (should (executable-find "sh" 'remote)))
 
       ;; Cleanup.
       (tramp-cleanup-connection tramp-test-vec 'keep-debug 'keep-password)
@@ -6129,7 +6023,7 @@ INPUT, if non-nil, is a string sent to the process."
                  (string-equal
                   (make-auto-save-file-name)
                   (funcall
-                   (if quoted #'tramp-compat-file-name-quote #'identity)
+                   (if quoted #'file-name-quote #'identity)
                    (expand-file-name
                     (format "#%s#" (file-name-nondirectory tmp-name1))
                     ert-remote-temporary-file-directory))))))
@@ -6154,7 +6048,7 @@ INPUT, if non-nil, is a string sent to the process."
                          ("|" . "__")
                          ("[" . "_l")
                          ("]" . "_r"))
-                       (tramp-compat-file-name-unquote tmp-name1)))
+                       (file-name-unquote tmp-name1)))
                      tmp-name2)))
                   (should (file-directory-p tmp-name2)))))
 
@@ -6178,7 +6072,7 @@ INPUT, if non-nil, is a string sent to the process."
                          ("|" . "__")
                          ("[" . "_l")
                          ("]" . "_r"))
-                       (tramp-compat-file-name-unquote tmp-name1)))
+                       (file-name-unquote tmp-name1)))
                      tmp-name2)))
                   (should (file-directory-p tmp-name2)))))
 
@@ -6234,7 +6128,7 @@ INPUT, if non-nil, is a string sent to the process."
               (find-backup-file-name tmp-name1)
               (list
                (funcall
-                (if quoted #'tramp-compat-file-name-quote #'identity)
+                (if quoted #'file-name-quote #'identity)
                 (expand-file-name
                  (format "%s~" (file-name-nondirectory tmp-name1))
                  ert-remote-temporary-file-directory)))))))
@@ -6248,7 +6142,7 @@ INPUT, if non-nil, is a string sent to the process."
               (find-backup-file-name tmp-name1)
               (list
                (funcall
-                (if quoted #'tramp-compat-file-name-quote #'identity)
+                (if quoted #'file-name-quote #'identity)
                 (expand-file-name
                  (format
                   "%s~"
@@ -6277,7 +6171,7 @@ INPUT, if non-nil, is a string sent to the process."
                 (find-backup-file-name tmp-name1)
                 (list
                  (funcall
-                  (if quoted #'tramp-compat-file-name-quote #'identity)
+                  (if quoted #'file-name-quote #'identity)
                   (expand-file-name
                    (format
                     "%s~"
@@ -6308,7 +6202,7 @@ INPUT, if non-nil, is a string sent to the process."
                 (find-backup-file-name tmp-name1)
                 (list
                  (funcall
-                  (if quoted #'tramp-compat-file-name-quote #'identity)
+                  (if quoted #'file-name-quote #'identity)
                   (expand-file-name
                    (format
                     "%s~"
@@ -6566,7 +6460,6 @@ INPUT, if non-nil, is a string sent to the process."
             (tramp-cleanup-connection
              tramp-test-vec 'keep-debug 'keep-password)))))))
 
-;; The functions were introduced in Emacs 26.1.
 (ert-deftest tramp-test40-make-nearby-temp-file ()
   "Check `make-nearby-temp-file' and `temporary-file-directory'."
   (skip-unless (tramp--test-enabled))
@@ -6598,12 +6491,6 @@ INPUT, if non-nil, is a string sent to the process."
     (delete-directory tmp-file)
     (should-not (file-exists-p tmp-file))))
 
-(defun tramp--test-emacs27-p ()
-  "Check for Emacs version >= 27.1.
-Some semantics has been changed for there, without new functions
-or variables, so we check the Emacs version directly."
-  (>= emacs-major-version 27))
-
 (defun tramp--test-emacs28-p ()
   "Check for Emacs version >= 28.1.
 Some semantics has been changed for there, without new functions
@@ -6638,7 +6525,7 @@ This is used in tests which we don't want to tag
                          :body nil :tags '(:tramp-asynchronous-processes))))
    ;; tramp-adb.el cannot apply multi-byte commands.
    (not (and (tramp--test-adb-p)
-             (string-match-p (tramp-compat-rx multibyte) default-directory)))))
+             (string-match-p (rx multibyte) default-directory)))))
 
 (defun tramp--test-crypt-p ()
   "Check, whether the remote directory is encrypted."
@@ -6802,10 +6689,7 @@ This requires restrictions of file name syntax."
 
 (defun tramp--test-check-files (&rest files)
   "Run a simple but comprehensive test over every file in FILES."
-  ;; `filename-non-special' has been fixed in Emacs 27.1, see Bug#29579.
-  (dolist (quoted
-           (if (and (tramp--test-expensive-test-p) (tramp--test-emacs27-p))
-               '(nil t) '(nil)))
+  (dolist (quoted (if (tramp--test-expensive-test-p) '(nil t) '(nil)))
     ;; We must use `file-truename' for the temporary directory,
     ;; because it could be located on a symlinked directory.  This
     ;; would let the test fail.
@@ -6855,7 +6739,7 @@ This requires restrictions of file name syntax."
                   (should
                    (string-equal
                     (funcall
-                     (if quoted #'tramp-compat-file-name-quote #'identity)
+                     (if quoted #'file-name-quote #'identity)
                      (file-attribute-type (file-attributes file3)))
                     (file-remote-p (file-truename file1) 'localname)))
                   ;; Check file contents.
@@ -6946,14 +6830,14 @@ This requires restrictions of file name syntax."
                     (should
                      (string-equal
                       (caar (directory-files-and-attributes
-                             file1 nil (tramp-compat-rx (literal elt1))))
+                             file1 nil (rx (literal elt1))))
                       elt1))
                     (should
                      (string-equal
                       (funcall
-                       (if quoted #'tramp-compat-file-name-quote #'identity)
+                       (if quoted #'file-name-quote #'identity)
                        (cadr (car (directory-files-and-attributes
-                                   file1 nil (tramp-compat-rx (literal elt1))))))
+                                   file1 nil (rx (literal elt1))))))
                       (file-remote-p (file-truename file2) 'localname)))
                     (delete-file file3)
                     (should-not (file-exists-p file3))))
@@ -6962,15 +6846,7 @@ This requires restrictions of file name syntax."
                 ;; `default-directory' with special characters.  See
                 ;; Bug#53846.
                 (when (and (tramp--test-expensive-test-p)
-                           (tramp--test-supports-processes-p)
-                           ;; Prior Emacs 27, `shell-file-name' was
-                           ;; hard coded as "/bin/sh" for remote
-                           ;; processes in Emacs.  That doesn't work
-                           ;; for tramp-adb.el.  tramp-sshfs.el times
-                           ;; out for older Emacsen, reason unknown.
-                           (or (and (not (tramp--test-adb-p))
-                                    (not (tramp--test-sshfs-p)))
-                               (tramp--test-emacs27-p)))
+                           (tramp--test-supports-processes-p))
                   (let ((default-directory file1))
                     (dolist (this-shell-command
                              (append
@@ -7008,7 +6884,7 @@ This requires restrictions of file name syntax."
                     (goto-char (point-min))
                     (should
                      (re-search-forward
-                      (tramp-compat-rx
+                      (rx
                        bol (literal envvar)
                        "=" (literal (getenv envvar)) eol))))))))
 
@@ -7154,13 +7030,8 @@ This requires restrictions of file name syntax."
 (ert-deftest tramp-test43-file-system-info ()
   "Check that `file-system-info' returns proper values."
   (skip-unless (tramp--test-enabled))
-  ;; Since Emacs 27.1.
-  (skip-unless (fboundp 'file-system-info))
 
-  ;; `file-system-info' exists since Emacs 27.1.  We don't want to see
-  ;; compiler warnings for older Emacsen.
-  (when-let ((fsi (with-no-warnings
-                    (file-system-info ert-remote-temporary-file-directory))))
+  (when-let ((fsi (file-system-info ert-remote-temporary-file-directory)))
     (should (consp fsi))
     (should (= (length fsi) 3))
     (dotimes (i (length fsi))
@@ -7216,10 +7087,6 @@ process sentinels.  They shall not disturb each other."
                      '(:unstable)))
   (skip-unless (tramp--test-enabled))
   (skip-unless (tramp--test-supports-processes-p))
-  ;; Prior Emacs 27, `shell-file-name' was hard coded as "/bin/sh" for
-  ;; remote processes in Emacs.  That doesn't work for tramp-adb.el.
-  (when (tramp--test-adb-p)
-    (skip-unless (tramp--test-emacs27-p)))
   (skip-unless (not (tramp--test-docker-p)))
   (skip-unless (not (tramp--test-telnet-p)))
   (skip-unless (not (tramp--test-sshfs-p)))
@@ -7552,7 +7419,7 @@ process sentinels.  They shall not disturb each other."
     (dolist (tm '(t nil))
       (should
        (string-match-p
-        (tramp-compat-rx
+        (rx
          "Tramp loaded: nil" (+ (any "\n\r"))
          "Tramp loaded: nil" (+ (any "\n\r"))
          "Tramp loaded: " (literal (symbol-name tm)) (+ (any "\n\r")))
@@ -7600,7 +7467,7 @@ process sentinels.  They shall not disturb each other."
             (tramp-cleanup-all-connections))"))
     (should
      (string-match-p
-      (tramp-compat-rx
+      (rx
        "Loading "
        (literal
         (expand-file-name