Fix instrumented eval-defun not printing "Edebug:" to the echo area

* lisp/progmodes/elisp-mode.el (elisp--eval-defun): Determine if we're
instrumenting a function and call eval-region with PRINTFLAG set to
nil if so (Bug#50245).

* test/lisp/progmodes/elisp-mode-tests.el
(eval-defun-prints-edebug-when-instrumented): Add a new test.

lisp/progmodes/elisp-mode.el

@@ -1646,6 +1646,7 @@ Return the result of evaluation."
   ;; printing, not while evaluating.
   (defvar elisp--eval-defun-result)
   (let ((debug-on-error eval-expression-debug-on-error)
+        (edebugging edebug-all-defs)
         elisp--eval-defun-result)
     (save-excursion
       ;; Arrange for eval-region to "read" the (possibly) altered form.
@@ -1670,8 +1671,9 @@ Return the result of evaluation."
                          (elisp--eval-defun-1
                           (macroexpand form)))))
 	      (print-length eval-expression-print-length)
-	      (print-level eval-expression-print-level))
-          (eval-region beg end standard-output
+	      (print-level eval-expression-print-level)
+              (should-print (if (not edebugging) standard-output)))
+          (eval-region beg end should-print
                        (lambda (_ignore)
                          ;; Skipping to the end of the specified region
                          ;; will make eval-region return.

test/lisp/progmodes/elisp-mode-tests.el

@@ -183,6 +183,16 @@
         (call-interactively #'eval-last-sexp)
         (should (equal (current-message) "66 (#o102, #x42, ?B)"))))))
 
+;;; eval-defun
+
+(ert-deftest eval-defun-prints-edebug-when-instrumented ()
+  (skip-unless (not noninteractive))
+  (with-temp-buffer
+    (let ((current-prefix-arg '(4)))
+      (erase-buffer) (insert "(defun foo ())") (message nil)
+      (call-interactively #'eval-defun)
+      (should (equal (current-message) "Edebug: foo")))))
+
 ;;; eldoc
 
 (defun elisp-mode-tests--face-propertized-string (string)