Make js-beginning-of-defun return non-nil on success

The docstring of 'beginning-of-defun-function' says that the
function shall return non-nil when it found the beginning
of a defun.  This is specially important because the calling
code decides when to move point depending on the return value.
* lisp/progmodes/js.el (js-beginning-of-defun)
(js--beginning-of-defun-flat): Return non-nil when the beginning
of a defun is found.  (Bug#64283)

* test/lisp/progmodes/js-tests.el (js-mode-end-of-defun): Add a unit
test.

lisp/progmodes/js.el

@@ -1024,11 +1024,13 @@ Return the pitem of the function we went to the beginning of."
   "Helper function for `js-beginning-of-defun'."
   (let ((pstate (js--beginning-of-defun-raw)))
     (when pstate
-      (goto-char (js--pitem-h-begin (car pstate))))))
+      (goto-char (js--pitem-h-begin (car pstate)))
+      t)))
 
 (defun js-beginning-of-defun (&optional arg)
   "Value of `beginning-of-defun-function' for `js-mode'."
   (setq arg (or arg 1))
+  (let ((found))
     (while (and (not (eobp)) (< arg 0))
       (cl-incf arg)
       (when (and (not js-flat-functions)
@@ -1038,8 +1040,10 @@ Return the pitem of the function we went to the beginning of."
 
       (if (js--re-search-forward
            "\\_<function\\_>" nil t)
-        (goto-char (js--function-prologue-beginning))
-      (goto-char (point-max))))
+          (progn (goto-char (js--function-prologue-beginning))
+                 (setq found t))
+        (goto-char (point-max))
+        (setq found nil)))
 
     (while (> arg 0)
       (cl-decf arg)
@@ -1050,12 +1054,15 @@ Return the pitem of the function we went to the beginning of."
 
       (let ((prologue-begin (js--function-prologue-beginning)))
         (cond ((and prologue-begin (< prologue-begin (point)))
-             (goto-char prologue-begin))
+               (goto-char prologue-begin)
+               (setq found t))
 
               (js-flat-functions
-             (js--beginning-of-defun-flat))
+               (setq found (js--beginning-of-defun-flat)))
               (t
-             (js--beginning-of-defun-nested))))))
+               (when (js--beginning-of-defun-nested)
+                 (setq found t))))))
+    found))
 
 (defun js--flush-caches (&optional beg _ignored)
   "Flush the `js-mode' syntax cache after position BEG.

test/lisp/progmodes/js-tests.el

@@ -237,6 +237,57 @@ if (!/[ (:,='\"]/.test(value)) {
 (js-deftest-indent "jsx-unclosed-2.jsx")
 (js-deftest-indent "jsx.jsx")
 
+;;;; Navigation tests.
+
+(ert-deftest js-mode-beginning-of-defun ()
+  (with-temp-buffer
+    (insert "function foo() {
+  var value = 1;
+}
+
+/** A comment. */
+function bar() {
+  var value = 1;
+}
+")
+    (js-mode)
+    ;; Move point inside `foo'.
+    (goto-char 18)
+    (beginning-of-defun)
+    (should (bobp))
+    ;; Move point between the two functions.
+    (goto-char 37)
+    (beginning-of-defun)
+    (should (bobp))
+    ;; Move point inside `bar'.
+    (goto-char 73)
+    (beginning-of-defun)
+    ;; Point should move to the beginning of `bar'.
+    (should (equal (point) 56))))
+
+(ert-deftest js-mode-end-of-defun ()
+  (with-temp-buffer
+    (insert "function foo() {
+  var value = 1;
+}
+
+/** A comment. */
+function bar() {
+  var value = 1;
+}
+")
+    (js-mode)
+    (goto-char (point-min))
+    (end-of-defun)
+    ;; end-of-defun from the beginning of the buffer should go to the
+    ;; end of `foo'.
+    (should (equal (point) 37))
+    ;; Move point to the beginning of /** A comment. */
+    (goto-char 38)
+    (end-of-defun)
+    ;; end-of-defun should move point to eob.
+    (should (eobp))))
+
 (provide 'js-tests)
 
 ;;; js-tests.el ends here