alist-get: Add optional arg TESTFN

If TESTFN is non-nil, then it is the predicate to lookup
the alist.  Otherwise, use 'eq' (Bug#27584).
* lisp/subr.el (alist-get): Add optional arg FULL.
* lisp/emacs-lisp/map.el (map-elt, map-put): Add optional arg TESTFN.
* lisp/emacs-lisp/gv.el (alist-get): Update expander.
* doc/lispref/lists.texi (Association Lists): Update manual.
* etc/NEWS: Announce the changes.
* test/lisp/emacs-lisp/map-tests.el (test-map-put-testfn-alist)
(test-map-elt-testfn): New tests.

2 files changed, 17 insertions, 10 deletions

diff --git a/lisp/emacs-lisp/gv.el b/lisp/emacs-lisp/gv.el
index c5c12a6414c..27376fc7f95 100644
--- a/lisp/emacs-lisp/gv.el
+++ b/lisp/emacs-lisp/gv.el
@@ -377,10 +377,12 @@ The return value is the last VAL in the list.
     `(with-current-buffer ,buf (set (make-local-variable ,var) ,v))))
 
 (gv-define-expander alist-get
-  (lambda (do key alist &optional default remove)
+  (lambda (do key alist &optional default remove testfn)
     (macroexp-let2 macroexp-copyable-p k key
       (gv-letplace (getter setter) alist
-        (macroexp-let2 nil p `(assq ,k ,getter)
+        (macroexp-let2 nil p `(if (and ,testfn (not (eq ,testfn 'eq)))
+                                  (assoc ,k ,getter ,testfn)
+                                (assq ,k ,getter))
           (funcall do (if (null default) `(cdr ,p)
                         `(if ,p (cdr ,p) ,default))
                    (lambda (v)
diff --git a/lisp/emacs-lisp/map.el b/lisp/emacs-lisp/map.el
index a89457e877d..31ba075c40f 100644
--- a/lisp/emacs-lisp/map.el
+++ b/lisp/emacs-lisp/map.el
@@ -4,7 +4,7 @@
 
 ;; Author: Nicolas Petton <nicolas@petton.fr>
 ;; Keywords: convenience, map, hash-table, alist, array
-;; Version: 1.1
+;; Version: 1.2
 ;; Package: map
 
 ;; Maintainer: emacs-devel@gnu.org
@@ -93,11 +93,13 @@ Returns the result of evaluating the form associated with MAP-VAR's type."
            ((arrayp ,map-var) ,(plist-get args :array))
            (t (error "Unsupported map: %s" ,map-var)))))
 
-(defun map-elt (map key &optional default)
+(defun map-elt (map key &optional default testfn)
   "Lookup KEY in MAP and return its associated value.
 If KEY is not found, return DEFAULT which defaults to nil.
 
-If MAP is a list, `eql' is used to lookup KEY.
+If MAP is a list, `eql' is used to lookup KEY.  Optional argument
+TESTFN, if non-nil, means use its function definition instead of
+`eql'.
 
 MAP can be a list, hash-table or array."
   (declare
@@ -106,30 +108,33 @@ MAP can be a list, hash-table or array."
       (gv-letplace (mgetter msetter) `(gv-delay-error ,map)
         (macroexp-let2* nil
             ;; Eval them once and for all in the right order.
-            ((key key) (default default))
+            ((key key) (default default) (testfn testfn))
           `(if (listp ,mgetter)
                ;; Special case the alist case, since it can't be handled by the
                ;; map--put function.
                ,(gv-get `(alist-get ,key (gv-synthetic-place
                                           ,mgetter ,msetter)
-                                    ,default)
+                                    ,default nil ,testfn)
                         do)
              ,(funcall do `(map-elt ,mgetter ,key ,default)
                        (lambda (v) `(map--put ,mgetter ,key ,v)))))))))
   (map--dispatch map
-    :list (alist-get key map default)
+    :list (alist-get key map default nil testfn)
     :hash-table (gethash key map default)
     :array (if (and (>= key 0) (< key (seq-length map)))
                (seq-elt map key)
              default)))
 
-(defmacro map-put (map key value)
+(defmacro map-put (map key value &optional testfn)
   "Associate KEY with VALUE in MAP and return VALUE.
 If KEY is already present in MAP, replace the associated value
 with VALUE.
+When MAP is a list, test equality with TESTFN if non-nil, otherwise use `eql'.
+TESTFN, if non-nil, means use its function definition instead of
+`eql'.
 
 MAP can be a list, hash-table or array."
-  `(setf (map-elt ,map ,key) ,value))
+  `(setf (map-elt ,map ,key nil ,testfn) ,value))
 
 (defun map-delete (map key)
   "Delete KEY from MAP and return MAP.