chore: add web server script that avoids bogus caching

README.md

@@ -49,7 +49,7 @@ lake exe generate-manual --depth 2
 
 Then run a local web server on its output:
 ```
-python3 -m http.server 8880 --directory _out/html-multi &
+python3 ./server.py 8880 &
 ```
 
 Then open <http://localhost:8880> in your browser.

server.py

@@ -0,0 +1,63 @@
+#!/usr/bin/env python3
+
+# This wrapper turns off the Python HTTP server's overly aggressive
+# cache headers, which can get in the way of Verso hovers.
+
+from http import server # Python 3
+from http.server import ThreadingHTTPServer, test
+import os
+
+
+class NonCachingHTTPRequestHandler(server.SimpleHTTPRequestHandler):
+    def end_headers(self):
+        self.send_my_headers()
+        server.SimpleHTTPRequestHandler.end_headers(self)
+
+    def send_my_headers(self):
+        self.send_header("Cache-Control", "no-cache, no-store, must-revalidate")
+        self.send_header("Pragma", "no-cache")
+        self.send_header("Expires", "0")
+
+if __name__ == '__main__':
+    import argparse
+    import contextlib
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('-b', '--bind', metavar='ADDRESS',
+                        help='bind to this address '
+                             '(default: all interfaces)')
+    parser.add_argument('-d', '--directory', default="_out/html-multi",
+                        help='serve this directory '
+                             '(default: _out/html-multi)')
+    parser.add_argument('-p', '--protocol', metavar='VERSION',
+                        default='HTTP/1.0',
+                        help='conform to this HTTP version '
+                             '(default: %(default)s)')
+    parser.add_argument('port', default=8000, type=int, nargs='?',
+                        help='bind to this port '
+                             '(default: %(default)s)')
+    args = parser.parse_args()
+
+    # ensure dual-stack is not disabled; ref #38907
+    class DualStackServer(ThreadingHTTPServer):
+
+        def server_bind(self):
+            # suppress exception when protocol is IPv4
+            with contextlib.suppress(Exception):
+                self.socket.setsockopt(
+                    socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0)
+            return super().server_bind()
+
+        def finish_request(self, request, client_address):
+            self.RequestHandlerClass(request, client_address, self,
+                                     directory=args.directory)
+
+    print(args)
+
+    test(
+        HandlerClass=NonCachingHTTPRequestHandler,
+        ServerClass=DualStackServer,
+        port=args.port,
+        bind=args.bind,
+        protocol=args.protocol,
+    )