Add an optional testfn parameter to assoc

* src/fns.c (assoc): New optional testfn parameter used for comparison
when provided.
* test/src/fns-tests.el (test-assoc-testfn): Add tests for the new
'testfn' parameter.
* src/buffer.c:
* src/coding.c:
* src/dbusbind.c:
* src/font.c:
* src/fontset.c:
* src/gfilenotify.c:
* src/image.c:
* src/keymap.c:
* src/process.c:
* src/w32fns.c:
* src/w32font.c:
* src/w32notify.c:
* src/w32term.c:
* src/xdisp.c:
* src/xfont.c: Add a third argument to Fassoc calls.
* etc/NEWS:
* doc/lispref/lists.texi: Document the new 'testfn' parameter.

1 files changed, 6 insertions, 0 deletions

diff --git a/test/src/fns-tests.el b/test/src/fns-tests.el
index 2e463455f0c..e294859226c 100644
--- a/test/src/fns-tests.el
+++ b/test/src/fns-tests.el
@@ -373,6 +373,12 @@
     (should-error (assoc 3 d1) :type 'wrong-type-argument)
     (should-error (assoc 3 d2) :type 'wrong-type-argument)))
 
+(ert-deftest test-assoc-testfn ()
+  (let ((alist '(("a" . 1) ("b" . 2))))
+    (should-not (assoc "a" alist #'ignore))
+    (should (eq (assoc "b" alist #'string-equal) (cadr alist)))
+    (should-not (assoc "b" alist #'eq))))
+
 (ert-deftest test-cycle-rassq ()
   (let ((c1 (cyc1 '(0 . 1)))
         (c2 (cyc2 '(0 . 1) '(0 . 2)))