From cfe89a74a63e8205782b7217ae01145b54a27fcc Mon Sep 17 00:00:00 2001
From: Daniel Mendler <mail@daniel-mendler.de>
Date: Mon, 12 May 2025 23:58:22 +0200
Subject: compat-31: New function hash-table-contains-p

---
 NEWS.org        | 1 +
 compat-31.el    | 6 ++++++
 compat-tests.el | 8 ++++++++
 compat.texi     | 5 +++++
 4 files changed, 20 insertions(+)

diff --git a/NEWS.org b/NEWS.org
index e51f4f2..086de05 100644
--- a/NEWS.org
+++ b/NEWS.org
@@ -15,6 +15,7 @@
 - compat-31: New macro =with-work-buffer=.
 - compat-31: New function =unbuttonize-region=.
 - compat-31: New extended function =seconds-to-string=.
+- compat-31: New function =hash-table-contains-p=.
 - Drop support for Emacs 24.x. Emacs 25.1 is required now. In case
   Emacs 24.x support is still needed, Compat 30 can be used.
 
diff --git a/compat-31.el b/compat-31.el
index b6aa5e3..e27ef0f 100644
--- a/compat-31.el
+++ b/compat-31.el
@@ -29,6 +29,12 @@
 
 ;;;; Defined in subr.el
 
+(compat-defun hash-table-contains-p (key table) ;; <compat-tests:hash-table-contains-p>
+  "Return non-nil if TABLE has an element with KEY."
+  (declare (side-effect-free t))
+  (let ((missing '#:missing))
+    (not (eq (gethash key table missing) missing))))
+
 (compat-defmacro static-when (condition &rest body) ;; <compat-tests:static-when>
   "A conditional compilation macro.
 Evaluate CONDITION at macro-expansion time.  If it is non-nil,
diff --git a/compat-tests.el b/compat-tests.el
index 5d70ac5..8bfc502 100644
--- a/compat-tests.el
+++ b/compat-tests.el
@@ -3012,6 +3012,14 @@
   (with-temp-buffer
     (should-equal (take 3 (widget-create 'key)) '(key :value ""))))
 
+(ert-deftest compat-hash-table-contains-p ()
+  (let ((h (make-hash-table :test #'equal)))
+    (puthash :foo t h)
+    (should (hash-table-contains-p :foo h))
+    (should-not (hash-table-contains-p :bar h))
+    (should-not (hash-table-contains-p 'missing h))
+    (should-not (hash-table-contains-p '#:missing h))))
+
 (ert-deftest compat-copy-tree ()
   ;; Adapted from Emacs /test/lisp/subr-tests.el
   ;; Check that values other than conses, vectors and records are
diff --git a/compat.texi b/compat.texi
index 2b81e7e..d9f9358 100644
--- a/compat.texi
+++ b/compat.texi
@@ -3452,6 +3452,11 @@ older than 31.1.  Note that due to upstream changes, it might happen
 that there will be the need for changes, so use these functions with
 care.
 
+@c based on lisp/subr.el
+@defmac hash-table-contains-p key table
+Return non-nil if @var{table} has an element with @var{key}.
+@end defmac
+
 @c copied from lispref/control.texi
 @defmac static-when condition body...
 Test @var{condition} at macro-expansion time.  If its value is
-- 
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