Copy over upstream Compat macros to erc-compat

* lisp/erc/erc-backend: (erc--get-isupport-entry): Replace call to
`erc-compat--with-memoization' with the built-in `with-memoization'.
* lisp/erc/erc-compat.el: (erc-compat-function, erc-compat-call): Add
new macros from Compat 29.1.2.0.
(erc-compat--with-memoization): Remove because it's now provided by
Compat.  (Bug#60954.)

2 files changed, 44 insertions, 10 deletions

diff --git a/lisp/erc/erc-backend.el b/lisp/erc/erc-backend.el
index 84d6b8a7efd..bdf4e2ddca2 100644
--- a/lisp/erc/erc-backend.el
+++ b/lisp/erc/erc-backend.el
@@ -1984,7 +1984,7 @@ ambiguous and only useful for tokens supporting a single
 primitive value."
   (if-let* ((table (or erc--isupport-params
                        (erc-with-server-buffer erc--isupport-params)))
-            (value (erc-compat--with-memoization (gethash key table)
+            (value (with-memoization (gethash key table)
                      (when-let ((v (assoc (symbol-name key)
                                           erc-server-parameters)))
                        (if (cdr v)
diff --git a/lisp/erc/erc-compat.el b/lisp/erc/erc-compat.el
index e6ae62d3a2e..10a495211cc 100644
--- a/lisp/erc/erc-compat.el
+++ b/lisp/erc/erc-compat.el
@@ -34,6 +34,49 @@
 (require 'compat nil 'noerror)
 (eval-when-compile (require 'cl-lib) (require 'url-parse))
 
+;; Except for the "erc-" namespacing, these two definitions should be
+;; continuously updated to match the latest upstream ones verbatim.
+;; Although they're pretty simple, it's likely not worth checking for
+;; and possibly deferring to the non-prefixed versions.
+;;
+;; BEGIN Compat macros
+
+;;;; Macros for extended compatibility function calls
+
+(defmacro erc-compat-function (fun)
+  "Return compatibility function symbol for FUN.
+
+If the Emacs version provides a sufficiently recent version of
+FUN, the symbol FUN is returned itself.  Otherwise the macro
+returns the symbol of a compatibility function which supports the
+behavior and calling convention of the current stable Emacs
+version.  For example Compat 29.1 will provide compatibility
+functions which implement the behavior and calling convention of
+Emacs 29.1.
+
+See also `compat-call' to directly call compatibility functions."
+  (let ((compat (intern (format "compat--%s" fun))))
+    `#',(if (fboundp compat) compat fun)))
+
+(defmacro erc-compat-call (fun &rest args)
+  "Call compatibility function or macro FUN with ARGS.
+
+A good example function is `plist-get' which was extended with an
+additional predicate argument in Emacs 29.1.  The compatibility
+function, which supports this additional argument, can be
+obtained via (compat-function plist-get) and called
+via (compat-call plist-get plist prop predicate).  It is not
+possible to directly call (plist-get plist prop predicate) on
+Emacs older than 29.1, since the original `plist-get' function
+does not yet support the predicate argument.  Note that the
+Compat library never overrides existing functions.
+
+See also `compat-function' to lookup compatibility functions."
+  (let ((compat (intern (format "compat--%s" fun))))
+    `(,(if (fboundp compat) compat fun) ,@args)))
+
+;; END Compat macros
+
 ;;;###autoload(autoload 'erc-define-minor-mode "erc-compat")
 (define-obsolete-function-alias 'erc-define-minor-mode
   #'define-minor-mode "28.1")
@@ -368,15 +411,6 @@ If START or END is negative, it counts from the end."
 
 ;;;; Misc 29.1
 
-(defmacro erc-compat--with-memoization (table &rest forms)
-  (declare (indent defun))
-  (cond
-   ((fboundp 'with-memoization)
-    `(with-memoization ,table ,@forms)) ; 29.1
-   ((fboundp 'cl--generic-with-memoization)
-    `(cl--generic-with-memoization ,table ,@forms))
-   (t `(progn ,@forms))))
-
 (defvar url-irc-function)
 
 (defun erc-compat--29-browse-url-irc (string &rest _)