[2.0 rc.16 – rc.19 / next] Incomplete #4207 fix: an unread pending memo behind an intermediate memo still holds a latest()-mounted <Loading> #4340

Describe the bug

This is the case #4203 describes, with one extra memo between the written signal and the never-settling memo. The fix for #4203 (#4207, 0117658bee) does not cover it.

A <Loading> mounted by a keyed <Show> whose condition reads latest(value) ?? value() stays on its fallback forever when the component inside it:

1. writes an ownedWrite signal during mount;
2. derives a memo from that signal;
3. creates a memo that reads the derived memo and returns a promise that never settles.

Nothing reads the pending memo, and the component renders static text. As in #4203, a pending value that no render effect reaches should not hold the boundary.

Your Example Website or App

Inline below: a self-contained vitest + jsdom test, solid-js / @solidjs/web only.

Steps to Reproduce the Bug or Issue

repro.test.jsx:

import { render } from "@solidjs/web";
import { createMemo, createSignal, latest, Loading, Show } from "solid-js";
import { expect, it } from "vitest";

const wait = (ms) => new Promise((r) => setTimeout(r, ms));

it("an unread pending memo behind an intermediate memo does not hold a latest()-mounted <Loading>", async () => {
  const el = document.createElement("div");
  function Child() {
    const [version, setVersion] = createSignal(0, { ownedWrite: true });
    setVersion(1);
    const gate = createMemo(() => version()); // reading version() directly here passes since #4207
    createMemo(() => (gate(), new Promise(() => {}))); // never read, never settles
    return <p>child</p>;
  }
  render(() => {
    const value = createMemo(async () => "v");
    return (
      <Loading fallback={<p>outer</p>}>
        <Show when={latest(value) ?? value()} keyed>
          {() => <Loading fallback={<p>inner</p>}><Child /></Loading>}
        </Show>
      </Loading>
    );
  }, el);
  await wait(100);
  expect(el.textContent).toBe("child");
});

{
  "private": true,
  "type": "module",
  "dependencies": {
    "solid-js": "2.0.0-rc.19", "@solidjs/web": "2.0.0-rc.19", "@solidjs/signals": "2.0.0-rc.19",
    "@solidjs/babel-plugin": "2.0.0-rc.19", "@babel/core": "7.28.5",
    "vitest": "3.2.4", "vite": "7.1.12", "jsdom": "26.1.0"
  },
  "pnpm": { "overrides": { "solid-js": "2.0.0-rc.19", "@solidjs/web": "2.0.0-rc.19", "@solidjs/signals": "2.0.0-rc.19" } }
}

// vitest.config.mjs
import { transformAsync } from "@babel/core";
import solid from "@solidjs/babel-plugin";
const conditions = ["browser", "development"];
export default {
  plugins: [{
    name: "solid-jsx", enforce: "pre",
    async transform(code, id) {
      if (!id.endsWith(".jsx")) return null;
      const r = await transformAsync(code, { filename: id, babelrc: false, configFile: false, sourceMaps: true,
        plugins: [[solid, { generate: "dom", hydratable: false }]] });
      return { code: r.code, map: r.map };
    },
  }],
  resolve: { conditions },
  ssr: { resolve: { conditions, externalConditions: conditions }, noExternal: [/solid-js/, /@solidjs\//] },
  test: { environment: "jsdom", server: { deps: { inline: [/solid-js/, /@solidjs\//] } } },
};

Expected behavior

child, as on rc.13 – rc.15. Actual on rc.16 – rc.19 and on next@17d4d1b: inner, forever.

Each of these makes the test pass on rc.19:

• the pending memo reads version() directly instead of gate() (the [2.0 rc.16] A <Loading> mounted through latest() never reveals while an unread memo stays pending (regression from dc063a65, #4171) #4203 shape, fixed by fix(signals): an unread pending memo does not hold a verdict-mounted Loading (#4203) #4207);
• when={value()} without latest;
• no write, or doing the write from createEffect / createRenderEffect.

Screenshots or Videos

No response

Platform

• OS: macOS
• Runtime: Node 25.8.2, vitest 3.2.4, jsdom 26.1.0, @solidjs/babel-plugin (generate dom). Originally seen in Chromium: screens under a latest-gated shell never leave the fallback when a sibling query is disabled.
• Version: solid-js / @solidjs/web / @solidjs/signals 2.0.0-rc.19. Also reproduces on next@17d4d1b (signals built from source).

Additional context

Bisect. Signals built from source between the rc.15 and rc.16 release commits, with solid-js and @solidjs/web at rc.16. The first bad commit is dc063a6 fix(signals): a verdict-mounted Loading holds a nested render effect's first read (#4166) (#4171), the same commit as #4203.

Usage. The signal options reference describes ownedWrite as "Suppress dev-mode warnings when writing inside an owned scope". The migration guide says: "Reserve ownedWrite: true for an internal signal that intentionally accepts in-scope writes." A data-fetching adapter is that case. It bumps a version signal while its first compute runs, and a sibling disabled query's data memo derives from it and stays pending.