Add helpers to dynamically assign connection-local values

* lisp/files-x.el (connection-local-criteria)
(connection-local-profile-name-for-setq): New variables.
(with-connection-local-variables-1): ... let-bind them here.
(connection-local-update-profile-variables)
(connection-local-profile-name-for-criteria): New functions.
(with-connection-local-application-variables, setq-connection-local):
New macros.

* test/lisp/files-x-tests.el: Require 'tramp-integration'
(files-x-test--variable5, remote-lazy-var): New variables.
(files-x-test-hack-connection-local-variables-apply): Expand checks.
(files-x-test-with-connection-local-variables): Remove
'hack-connection-local-variables-apply' check (it belongs in the above
test), and expand some other checks.
(files-x-test--get-lazy-var, files-x-test--set-lazy-var): New
functions.
(files-x-test-connection-local-update-profile-variables)
(files-x-test-setq-connection-local): New tests.

* doc/lispref/variables.texi (Connection Local Variables): Split into
two subsections and document the new features.

* etc/NEWS: Announce 'setq-connection-local'.

1 files changed, 107 insertions, 41 deletions

diff --git a/test/lisp/files-x-tests.el b/test/lisp/files-x-tests.el
index 2f6d0d4a991..b1555a02664 100644
--- a/test/lisp/files-x-tests.el
+++ b/test/lisp/files-x-tests.el
@@ -23,6 +23,7 @@
 
 (require 'ert)
 (require 'files-x)
+(require 'tramp-integration)
 
 (defconst files-x-test--variables1
   '((remote-shell-file-name . "/bin/bash")
@@ -35,7 +36,11 @@
   '((remote-null-device . "/dev/null")))
 (defconst files-x-test--variables4
   '((remote-null-device . "null")))
+(defconst files-x-test--variables5
+  '((remote-lazy-var . nil)
+    (remote-null-device . "/dev/null")))
 (defvar remote-null-device)
+(defvar remote-lazy-var nil)
 (put 'remote-shell-file-name 'safe-local-variable #'identity)
 (put 'remote-shell-command-switch 'safe-local-variable #'identity)
 (put 'remote-shell-interactive-switch 'safe-local-variable #'identity)
@@ -91,6 +96,28 @@
       (connection-local-get-profile-variables 'remote-nullfile)
       files-x-test--variables4))))
 
+(ert-deftest files-x-test-connection-local-update-profile-variables ()
+  "Test updating connection-local profile variables."
+
+  ;; Declare (PROFILE VARIABLES) objects.
+  (let (connection-local-profile-alist connection-local-criteria-alist)
+    (connection-local-set-profile-variables
+     'remote-bash (copy-alist files-x-test--variables1))
+    (should
+     (equal
+      (connection-local-get-profile-variables 'remote-bash)
+      files-x-test--variables1))
+
+    ;; Updating overwrites only the values specified in this call, but
+    ;; retains all the other values from previous calls.
+    (connection-local-update-profile-variables
+     'remote-bash files-x-test--variables2)
+    (should
+     (equal
+      (connection-local-get-profile-variables 'remote-bash)
+      (cons (car files-x-test--variables2)
+            (cdr files-x-test--variables1))))))
+
 (ert-deftest files-x-test-connection-local-set-profiles ()
   "Test setting connection-local profiles."
 
@@ -233,9 +260,12 @@
                  (nreverse (copy-tree files-x-test--variables2)))))
         ;; The variables exist also as local variables.
         (should (local-variable-p 'remote-shell-file-name))
+        (should (local-variable-p 'remote-null-device))
         ;; The proper variable value is set.
         (should
-         (string-equal (symbol-value 'remote-shell-file-name) "/bin/ksh"))))
+         (string-equal (symbol-value 'remote-shell-file-name) "/bin/ksh"))
+        (should
+         (string-equal (symbol-value 'remote-null-device) "/dev/null"))))
 
     ;; The third test case.  Both criteria `files-x-test--criteria1'
     ;; and `files-x-test--criteria2' apply, but there are no double
@@ -274,13 +304,11 @@
         (should-not (local-variable-p 'remote-shell-file-name))
         (should-not (boundp 'remote-shell-file-name))))))
 
-(defvar tramp-connection-local-default-shell-variables)
-(defvar tramp-connection-local-default-system-variables)
-
 (ert-deftest files-x-test-with-connection-local-variables ()
   "Test setting connection-local variables."
 
-  (let (connection-local-profile-alist connection-local-criteria-alist)
+  (let ((connection-local-profile-alist connection-local-profile-alist)
+        (connection-local-criteria-alist connection-local-criteria-alist))
     (connection-local-set-profile-variables
      'remote-bash files-x-test--variables1)
     (connection-local-set-profile-variables
@@ -292,29 +320,6 @@
      nil 'remote-ksh 'remote-nullfile)
 
     (with-temp-buffer
-      (let ((enable-connection-local-variables t))
-        (hack-connection-local-variables-apply nil)
-
-        ;; All connection-local variables are set.  They apply in
-        ;; reverse order in `connection-local-variables-alist'.
-        (should
-         (equal connection-local-variables-alist
-                (append
-                 (nreverse (copy-tree files-x-test--variables3))
-                 (nreverse (copy-tree files-x-test--variables2)))))
-        ;; The variables exist also as local variables.
-        (should (local-variable-p 'remote-shell-file-name))
-        (should (local-variable-p 'remote-null-device))
-        ;; The proper variable values are set.
-        (should
-         (string-equal (symbol-value 'remote-shell-file-name) "/bin/ksh"))
-        (should
-         (string-equal (symbol-value 'remote-null-device) "/dev/null"))
-
-        ;; A candidate connection-local variable is not bound yet.
-        (should-not (local-variable-p 'remote-shell-command-switch))))
-
-    (with-temp-buffer
       ;; Use the macro.  We need a remote `default-directory'.
       (let ((enable-connection-local-variables t)
             (default-directory "/method:host:")
@@ -331,18 +336,18 @@
         (with-connection-local-variables
          ;; All connection-local variables are set.  They apply in
          ;; reverse order in `connection-local-variables-alist'.
-         ;; Since we ha a remote default directory, Tramp's settings
+         ;; Since we have a remote default directory, Tramp's settings
          ;; are appended as well.
          (should
           (equal
            connection-local-variables-alist
            (append
-            (nreverse (copy-tree files-x-test--variables3))
-            (nreverse (copy-tree files-x-test--variables2))
             (nreverse
              (copy-tree tramp-connection-local-default-shell-variables))
             (nreverse
-             (copy-tree tramp-connection-local-default-system-variables)))))
+             (copy-tree tramp-connection-local-default-system-variables))
+            (nreverse (copy-tree files-x-test--variables3))
+            (nreverse (copy-tree files-x-test--variables2)))))
          ;; The variables exist also as local variables.
          (should (local-variable-p 'remote-shell-file-name))
          (should (local-variable-p 'remote-null-device))
@@ -352,15 +357,21 @@
          (should
           (string-equal (symbol-value 'remote-null-device) "/dev/null"))
 
-         ;; Run another instance of `with-connection-local-variables'
-         ;; with a different application.
-         (let ((connection-local-default-application (cadr files-x-test--application)))
-           (with-connection-local-variables
-            ;; The proper variable values are set.
-            (should
-             (string-equal (symbol-value 'remote-shell-file-name) "/bin/bash"))
-            (should
-             (string-equal (symbol-value 'remote-null-device) "/dev/null"))))
+         ;; Run `with-connection-local-application-variables' to use a
+         ;; different application.
+         (with-connection-local-application-variables
+             (cadr files-x-test--application)
+         (should
+          (equal
+           connection-local-variables-alist
+           (append
+            (nreverse (copy-tree files-x-test--variables3))
+            (nreverse (copy-tree files-x-test--variables1)))))
+           ;; The proper variable values are set.
+           (should
+            (string-equal (symbol-value 'remote-shell-file-name) "/bin/bash"))
+           (should
+            (string-equal (symbol-value 'remote-null-device) "/dev/null")))
          ;; The variable values are reset.
          (should
           (string-equal (symbol-value 'remote-shell-file-name) "/bin/ksh"))
@@ -376,5 +387,60 @@
         (should-not (boundp 'remote-shell-file-name))
         (should (string-equal (symbol-value 'remote-null-device) "null"))))))
 
+(defun files-x-test--get-lazy-var ()
+  "Get the connection-local value of `remote-lazy-var'.
+If it's not initialized yet, initialize it."
+  (with-connection-local-application-variables
+      (cadr files-x-test--application)
+    (or remote-lazy-var
+        (setq-connection-local remote-lazy-var
+                               (or (file-remote-p default-directory 'host)
+                                   "local")))))
+
+(defun files-x-test--set-lazy-var (value)
+  "Set the connection-local value of `remote-lazy-var'"
+  (with-connection-local-application-variables
+      (cadr files-x-test--application)
+    (setq-connection-local remote-lazy-var value)))
+
+(ert-deftest files-x-test-setq-connection-local ()
+  "Test dynamically setting connection local variables."
+  (let (connection-local-profile-alist connection-local-criteria-alist)
+    (connection-local-set-profile-variables
+     'remote-lazy files-x-test--variables5)
+    (connection-local-set-profiles
+     files-x-test--application
+     'remote-lazy)
+
+    ;; Test the initial local value.
+    (should (equal (files-x-test--get-lazy-var) "local"))
+
+    ;; Set the local value and make sure it retains the value we set.
+    (should (equal (files-x-test--set-lazy-var "here") "here"))
+    (should (equal (files-x-test--get-lazy-var) "here"))
+
+    (let ((default-directory "/method:host:"))
+      ;; Test the initial remote value.
+      (should (equal (files-x-test--get-lazy-var) "host"))
+
+      ;; Set the remote value and make sure it retains the value we set.
+      (should (equal (files-x-test--set-lazy-var "there") "there"))
+      (should (equal (files-x-test--get-lazy-var) "there"))
+      ;; Set another connection-local variable.
+      (with-connection-local-application-variables
+          (cadr files-x-test--application)
+        (setq-connection-local remote-null-device "null")))
+
+    ;; Make sure we get the local value we set above.
+    (should (equal (files-x-test--get-lazy-var) "here"))
+    (should-not (boundp 'remote-null-device))
+
+    ;; Make sure we get the remote values we set above.
+    (let ((default-directory "/method:host:"))
+      (should (equal (files-x-test--get-lazy-var) "there"))
+      (with-connection-local-application-variables
+          (cadr files-x-test--application)
+        (should (equal remote-null-device "null"))))))
+
 (provide 'files-x-tests)
 ;;; files-x-tests.el ends here