add no-cache headers for HTML/JS assets

apps/web/server.py

@@ -83,6 +83,50 @@ class ProxyStaticHandler(SimpleHTTPRequestHandler):
             return self._proxy_request()
         return super().do_GET()
 
+    def send_head(self):
+        import os
+        from urllib.parse import unquote
+        from http import HTTPStatus
+        path = self.translate_path(self.path)
+        f = None
+        if os.path.isdir(path):
+            parts = self.path.split("?", 1)
+            if not parts[0].endswith("/"):
+                self.send_response(HTTPStatus.MOVED_PERMANENTLY)
+                self.send_header("Location", parts[0] + "/")
+                self.end_headers()
+                return None
+            for index in "index.html", "index.htm":
+                index = os.path.join(path, index)
+                if os.path.exists(index):
+                    path = index
+                    break
+            else:
+                return self.list_directory(path)
+        ctype = self.guess_type(path)
+        try:
+            f = open(path, "rb")
+        except OSError:
+            self.send_error(HTTPStatus.NOT_FOUND, "File not found")
+            return None
+        try:
+            fs = os.fstat(f.fileno())
+            content_length = str(int(fs[6]))
+            self.send_response(HTTPStatus.OK)
+            self.send_header("Content-Type", ctype)
+            self.send_header("Content-Length", content_length)
+            if "text/html" in ctype or "text/javascript" in ctype or "application/javascript" in ctype:
+                self.send_header("Cache-Control", "no-cache, no-store, must-revalidate")
+                self.send_header("Pragma", "no-cache")
+                self.send_header("Expires", "0")
+            self.send_header("Last-Modified", self.date_time_string(fs.st_mtime))
+            self.end_headers()
+            return f
+        except:
+            f.close()
+            raise
+        return result
+
     def do_POST(self):
         if self.path.startswith("/api"):
             return self._proxy_request()