`lazy()`: remounting an already-loaded component renders empty (or the Suspense fallback) since 1.9.14

该 bug 位于 solid-js 源码中 lazy() 的客户端分支（dist/solid.js 构建产物指向该分支），其中 onCleanup 会在任一实例被销毁时清空共享的 comp 缓存。请阅读该分支以及在解析完成后设置 comp 的 load() 路径，然后检查是否有现有测试覆盖重试失败的导入。完成标准是：加载成功后重新挂载时同步渲染，导入失败后重新挂载仍会重试，且现有测试全部通过。

Describe the bug

Since 1.9.14, disposing any instance of a lazy() component clears the module-level component cache shared by all instances. The next mount of the same, already-loaded component creates a new resource and renders "" until it resolves. Inside <Suspense>, the fallback shows again. In 1.9.13 the remount renders the component synchronously.

This shows up as a visible flash whenever a lazily loaded page or overlay is closed and opened again.

Your Example Website or App

https://playground.solidjs.com/anonymous/08d6df4c-9789-4c96-8910-bb818f3fb391

Steps to Reproduce the Bug or Issue

Run test with solid version 1.9.17 from playground url. If you test it locally with solid 1.9.13 works as expected

import { createRoot, lazy, Suspense } from "solid-js";
import { render } from "solid-js/web";
import { createSignal } from "solid-js";

const flush = () => new Promise<void>((r) => setTimeout(r, 0));

function App() {
  const [lines, setLines] = createSignal<{ text: string; pass: boolean }[]>([]);

  async function runTest() {
    const out: { text: string; pass: boolean }[] = [];
    const check = (label: string, actual: unknown) => {
      const pass = actual === "loaded";
      out.push({ text: `${label}: ${JSON.stringify(actual)}`, pass });
    };

    // ── Case 1: without Suspense ──────────────────────────────
    const Lazy1 = lazy(() => Promise.resolve({ default: () => "loaded" }));
    let first1 = createRoot((d) => ({ d, v: Lazy1({}) }));
    await flush();
    first1.d();
    let second1 = createRoot((d) => ({ d, v: Lazy1({}) }));
    const r1 =
      typeof second1.v === "function" ? (second1.v as any)() : second1.v;
    check("without Suspense – remount", r1);
    second1.d();

    // ── Case 2: with Suspense ─────────────────────────────────
    const Lazy2 = lazy(() => Promise.resolve({ default: () => "loaded" }));
    const mkView = () =>
      Suspense({
        fallback: "fallback",
        get children() {
          return Lazy2({});
        },
      });
    let first2 = createRoot((d) => ({ d, v: mkView() }));
    await flush();
    first2.d();
    let second2 = createRoot((d) => ({ d, v: mkView() }));
    const r2 =
      typeof second2.v === "function" ? (second2.v as any)() : second2.v;
    check("with Suspense    – remount", r2);
    second2.d();

    setLines(out);
  }

  return (
    <div style="font-family:monospace;padding:1rem">
      <h2>lazy() remount regression · solid-js 1.9.14–1.9.17</h2>
      <p>
        Expected: <code>"loaded"</code> both times (solid-js 1.9.13 ✅)
      </p>
      <button onClick={runTest}>▶ Run test</button>
      <ul>
        {lines().map((l) => (
          <li style={`color:${l.pass ? "green" : "red"}`}>
            {l.pass ? "✅" : "❌"} {l.text}
          </li>
        ))}
      </ul>
    </div>
  );
}

render(() => <App />, document.getElementById("app")!);

Expected behavior

Once the module has loaded, a remount renders the component synchronously, as in 1.9.13:

== solid-js 1.9.13
without Suspense  first mount after load: "loaded", remount: "loaded"
with Suspense     first mount after load: "loaded", remount: "loaded"

Actual, in 1.9.14 through 1.9.17:

== solid-js 1.9.14
without Suspense  first mount after load: "loaded", remount: ""
with Suspense     first mount after load: "loaded", remount: "fallback"
== solid-js 1.9.17
without Suspense  first mount after load: "loaded", remount: ""
with Suspense     first mount after load: "loaded", remount: "fallback"

Cause

1.9.14 added an onCleanup in the client branch of lazy() (dist/solid.js):

     } else if (!comp) {
       const [s] = createResource(() => (p || (p = fn())).then(mod => mod.default));
       comp = s;
+      onCleanup(() => comp = undefined);
     }

comp is shared by every instance of the lazy() component, but the cleanup is registered on the owner of whichever instance created the resource. Disposing that one instance therefore clears the cache for all of them, even after the module has loaded. The next mount takes the !comp branch again and waits for a new resource. The module promise p is still cached, so nothing is re-downloaded, but the new resource resolves asynchronously, which causes the empty render or Suspense fallback.

Possible fix

If the cleanup is meant to let a failed import be retried on the next mount, it could clear the cache only when it still points at this instance's resource and that resource hasn't loaded. For example, against 1.9.17, where load() already sets comp = () => mod.default once the module resolves:

-      onCleanup(() => comp = undefined);
+      onCleanup(() => comp === s && (comp = undefined));

With this change, a remount after a successful load renders synchronously, and a remount after a failed import still retries.

Screenshots or Videos

No response

Platform

• OS: [macOS]
• solid-js: 1.9.14 to 1.9.17 (works in 1.9.13)
• Client build (dist/solid.cjs / dist/solid.js), no SSR or hydration
• Node 22 for the reproduction; we first saw it in a SolidJS app using the universal renderer

Additional context

No response