Make Vert.x test server Resource repeatable so the flaky-test retry works

[adamw]

Problem

The flaky-WebSocket-test retry added in #5410 (TestSuite.retries) did not actually rescue the Vert.x WS flake. On CI the retry ran but every attempt after the first failed instantly with:

ERROR DefaultCreateServerTest - Starting server failed because of null
java.lang.IllegalStateException
    at io.vertx.core.http.impl.CleanableHttpServer.listen(CleanableHttpServer.java:61)

Root cause

The three Vert.x test interpreters build the HTTP server eagerly, outside the Resource.make acquire:

val server = vertx.createHttpServer(...).requestHandler(router)  // captured once
val listenIO = vertxFutureToIo(server.listen(0))
Resource.make(listenIO)(...)

The retry re-runs the whole test, re-using the same server Resource, which calls listen() a second time on the same server instance. Vert.x 5's CleanableHttpServer.listen throws IllegalStateException (empty message → logged as "because of null") when its listenContext is already set. So the per-test server Resource simply wasn't repeatable — the shared Vert.x was never actually broken.

Fix

Create the server inside the acquire, so each acquire (and each retry) gets a fresh server:

val listenIO = IO.delay {
  val router = Router.router(vertx)
  val _ = route(router)
  vertx.createHttpServer(...).requestHandler(router)
}.flatMap(server => vertxFutureToIo(server.listen(0)))
Resource.make(listenIO)(s => vertxFutureToIo(s.close()).void).map(_.actualPort())

Applied to VertxTestServerInterpreter, CatsVertxTestServerInterpreter, ZioVertxTestServerInterpreter.

Test

ServerResourceRepeatableSpec acquires the server Resource twice (what the retry does). It throws the exact IllegalStateException on the old eager code and passes with this fix.

🤖 Generated with Claude Code