Add kvplist-merge function

README.creole

@@ -145,9 +145,11 @@ Filter the plist to just those matching //keys//.
 
 [[kvalist->filter-keys]] is actually used to do this work.
 
+=== kvplist->merge &rest plists ===
+
+Merge the 2nd and subsequent plists into the first, clobbering values set
+by lists to the left.
 
 === kvplist2->filter-keys plist2 &rest keys ===
 
 Return the //plist2// (a list of plists) filtered to the //keys//.
-
-

kv-tests.el

@@ -179,4 +179,19 @@
      (list :key1 "value1" :key2 t :key3 '(big list of symbols) :key4 10)
      'key1 'key4))))
 
+(ert-deftest kvplist-merge ()
+  (should
+   (equal
+    '(:key1 "value1" :key2 "new value" :key3 "entirely new")
+    (kvplist-merge '(:key1 "value1" :key2 "old value")
+                   '(:key2 "new value" :key3 "entirely new")))))
+
+(ert-deftest kvplist-merge-multiple ()
+  (should
+   (equal
+    '(:key1 "value1" :key2 "new value" :key3 "overwritten new one" :key4 "second entirely new")
+    (kvplist-merge '(:key1 "value1" :key2 "old value")
+                   '(:key2 "new value" :key3 "entirely new")
+                   '(:key3 "overwritten new one" :key4 "second entirely new")))))
+
 ;;; kv-tests.el ends here

kv.el

@@ -179,7 +179,7 @@ The keys are expected to be :prefixed and the colons are removed.
 The keys in the resulting alist are symbols."
   (when plist
     (loop for (key value . rest) on plist by 'cddr
-	  collect (cons (keyword->symbol key) value))))
+    collect (cons (keyword->symbol key) value))))
 
 (defun kvalist2->plist (alist2)
   "Convert a list of alists too a list of plists."
@@ -385,6 +385,15 @@ SEXP will describe the structure desired."
 
 (defalias 'map-bind 'kvmap-bind)
 
+(defun kvplist-merge (&rest plists)
+  "Merge the 2nd and subsequent plists into the first, clobbering values set by lists to the left."
+  (let ((result (car plists))
+        (plists (cdr plists)))
+    (loop for plist in plists do
+          (loop for (key val) on plist by 'cddr do
+                (setq result (plist-put result key val))))
+    result))
+
 (provide 'kv)
 (provide 'dotassoc)