[sse] Memory leak and missing cleanup when app-level retries are exhausted

[JavanPoirier]

Bug Report

Package: @solid-primitives/sse
File: packages/sse/src/sse.ts

---

Description

In createSSE, the handleError function inside _open correctly guards app-level reconnects behind the es.readyState === SSEReadyState.CLOSED check. However, when retriesLeft reaches 0 and the browser has permanently closed the connection, there is no cleanup performed. This causes:

1. currentCleanup is never called — source.close() and removeEventListener calls inside the makeSSE cleanup are never invoked, leaving the EventSource instance and its event listeners alive in memory.
2. source signal is never set to undefined — callers continue to see a stale SSESourceHandle.
3. currentCleanup reference is never cleared — the closure is retained unnecessarily.

---

Relevant Code

// packages/sse/src/sse.ts ~L258
if (es.readyState === SSEReadyState.CLOSED && retriesLeft > 0) {
  retriesLeft--;
  reconnectTimer = setTimeout(() => _open(resolvedUrl), reconnectConfig.delay ?? 3000);
}
// ❌ No else branch: when retriesLeft === 0, cleanup is never called

---

Expected Behavior

When retries are exhausted and es.readyState === CLOSED, the library should:

• Call currentCleanup() to invoke source.close() and remove all event listeners
• Set currentCleanup = undefined
• Set source signal to undefined

Suggested Fix

if (es.readyState === SSEReadyState.CLOSED && retriesLeft > 0) {
  retriesLeft--;
  reconnectTimer = setTimeout(() => _open(resolvedUrl), reconnectConfig.delay ?? 3000);
} else if (es.readyState === SSEReadyState.CLOSED) {
  // Retries exhausted — clean up fully to avoid memory/listener leaks
  currentCleanup?.();
  currentCleanup = undefined;
  setSource(undefined);
}

---

Steps to Reproduce

const { readyState } = createSSE("https://unreachable.example.com/events", {
  reconnect: { retries: 3, delay: 500 },
});
// After 3 failed attempts, event listeners remain attached and
// currentCleanup is never called.