Provide list of reloaded files (#2307)

* Allow access to reloaded files

* Return to simple boolean values

* Resolve before adding to changed files

sanic/reloader_helpers.py

@@ -47,16 +47,18 @@ def _get_args_for_reloading():
     return [sys.executable] + sys.argv
 
 
-def restart_with_reloader():
+def restart_with_reloader(changed=None):
     """Create a new process and a subprocess in it with the same arguments as
     this one.
     """
+    reloaded = ",".join(changed) if changed else ""
     return subprocess.Popen(
         _get_args_for_reloading(),
         env={
             **os.environ,
             "SANIC_SERVER_RUNNING": "true",
             "SANIC_RELOADER_PROCESS": "true",
+            "SANIC_RELOADED_FILES": reloaded,
         },
     )
 
@@ -94,24 +96,27 @@ def watchdog(sleep_interval, app):
 
     try:
         while True:
-            need_reload = False
 
+            changed = set()
             for filename in itertools.chain(
                 _iter_module_files(),
                 *(d.glob("**/*") for d in app.reload_dirs),
             ):
                 try:
-                    check = _check_file(filename, mtimes)
+                    if _check_file(filename, mtimes):
+                        path = (
+                            filename
+                            if isinstance(filename, str)
+                            else filename.resolve()
+                        )
+                        changed.add(str(path))
                 except OSError:
                     continue
 
-                if check:
-                    need_reload = True
-
-            if need_reload:
+            if changed:
                 worker_process.terminate()
                 worker_process.wait()
-                worker_process = restart_with_reloader()
+                worker_process = restart_with_reloader(changed)
 
             sleep(sleep_interval)
     except KeyboardInterrupt: