Allow ERC's module toggles access to the prefix arg

* lisp/erc/erc-common.el (erc--module-toggle-prefix-arg): Add internal
variable for preserving the `arg' passed to a module's minor-mode
toggle, which was previously discarded.  Doing this lets modules that
are more interactive in nature overload their mode toggles with
alternate behaviors.
(define-erc-module): Bind `erc--module-toggle-prefix-arg' to the `arg'
parameter, which is normally defined inside a `define-minor-mode' body
form.
* test/lisp/erc/erc-tests.el (define-erc-module--global,
define-erc-module--local): Expect activation body to be wrapped by a
let form binding `erc--module-toggle-prefix-arg'.  (Bug#63595)

1 files changed, 8 insertions, 6 deletions

diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index 3f36e7c94f6..cc69641fb0b 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -2204,9 +2204,10 @@ Some docstring."
                         :group (erc--find-group 'mname 'malias)
                         :require 'nil
                         :type "mname"
-                        (if erc-mname-mode
-                            (erc-mname-enable)
-                          (erc-mname-disable)))
+                        (let ((erc--module-toggle-prefix-arg arg))
+                          (if erc-mname-mode
+                              (erc-mname-enable)
+                            (erc-mname-disable))))
 
                       (defun erc-mname-enable ()
                         "Enable ERC mname mode."
@@ -2259,9 +2260,10 @@ ARG is omitted or nil.
 Some docstring."
                         :global nil
                         :group (erc--find-group 'mname nil)
-                        (if erc-mname-mode
-                            (erc-mname-enable)
-                          (erc-mname-disable)))
+                        (let ((erc--module-toggle-prefix-arg arg))
+                          (if erc-mname-mode
+                              (erc-mname-enable)
+                            (erc-mname-disable))))
 
                       (defun erc-mname-enable (&optional ,arg-en)
                         "Enable ERC mname mode.