racket/serialize: fix for submodules

Closes PR 12795

collects/racket/private/serialize.rkt

@@ -56,13 +56,17 @@
   ;;  then it can cause simplified module paths to be paths;
   ;;  keep the literal path, but marshal it to bytes.
   (define (protect-path p)
-    (if (path? p)
-	(path->bytes p)
-	p))
+    (cond
+     [(path? p) (path->bytes p)]
+     [(and (pair? p) (eq? (car p) 'submod) (path? (cadr p)))
+      `(submod ,(protect-path (cadr p)) . ,(cddr p))]
+     [else p]))
   (define (unprotect-path p)
-    (if (bytes? p)
-	(bytes->path p)
-	p))
+    (cond
+     [(bytes? p) (bytes->path p)]
+     [(and (pair? p) (eq? (car p) 'submod) (bytes? (cadr p)))
+      `(submod ,(unprotect-path (cadr p)) . ,(cddr p))]
+     [else p]))
 
   (define (revive-symbol s)
     (if (string? s)

collects/tests/racket/serialize.rktl

@@ -4,7 +4,8 @@
 
 (Section 'serialization)
 
-(require scheme/serialize)
+(require racket/serialize
+         racket/file)
 
 ;; ----------------------------------------
 
@@ -469,6 +470,24 @@
 (test #t pair? (serialize (new s:bad% [foo 10])))
 (err/rt-test (deserialize (serialize (new s:bad% [foo 10]))) exn:fail:object?)
 
+;; ----------------------------------------
+
+(let ([fn (make-temporary-file)])
+  (with-output-to-file fn
+    #:exists 'truncate
+    (lambda () (display
+                (string-append "#lang racket/base\n"
+                               "(require racket/serialize)\n"
+                               "(module+ main\n"
+                               "   (provide s)\n"
+                               "   (serializable-struct foo (bar))\n"
+                               "   (define s (serialize (foo 35))))\n"))))
+  (define s (dynamic-require `(submod ,fn main) 's))
+  (let ([o (open-output-bytes)])
+    (write s o)
+    (test s read (open-input-string (get-output-string o)))))
+
+
 ;; ----------------------------------------
 
 (report-errs)