* lisp/subr.el (when): Use `macroexp-progn'

* test/automated/subr-tests.el (subr-test-when): New test

lisp/subr.el

@@ -179,7 +179,7 @@ value of last one, or nil if there are none.
 
 \(fn COND BODY...)"
   (declare (indent 1) (debug t))
-  (list 'if cond (cons 'progn body)))
+  (list 'if cond (macroexp-progn body)))
 
 (defmacro unless (cond &rest body)
   "If COND yields nil, do BODY, else return nil.

test/automated/subr-tests.el

@@ -82,5 +82,19 @@
   (should (string-greaterp 'acb 'abc))
   (should (string-greaterp "acb" 'abc)))
 
+(ert-deftest subr-test-when ()
+  (should (equal (when t 1) 1))
+  (should (equal (when t 2) 2))
+  (should (equal (when nil 1) nil))
+  (should (equal (when nil 2) nil))
+  (should (equal (when t 'x 1) 1))
+  (should (equal (when t 'x 2) 2))
+  (should (equal (when nil 'x 1) nil))
+  (should (equal (when nil 'x 2) nil))
+  (should (equal (macroexpand-all '(when a b))
+                 '(if a b)))
+  (should (equal (macroexpand-all '(when a b c d))
+                 '(if a (progn b c d)))))
+
 (provide 'subr-tests)
 ;;; subr-tests.el ends here