vize:croquis/cf/reactivity-outside-setup

A reactive API is called outside setup.

Default severity: Not emitted
Applies to: Analyzed component graph and the supported facts described below
Automatic fix: None; review related files and apply the repair
Options: No per-code options; supported CLI findings accept severity overrides

This is a published diagnostic contract without a current producer. The Bad/Good scenario below explains the risk and repair; no flag currently makes this code trigger.

Vue permits ref/reactive/computed outside component setup. The risk here is unwanted ownership/sharing under an explicit instance-isolation policy, not API illegality. This contract has no current producer.

Shared project files

Use these unchanged files in both Bad and Good. Install the imported packages in the project: Vue, plus vue-router or Pinia where shown. Follow any version-specific support note. The entry root makes the component relationship explicit.

main.ts

import { createApp } from 'vue';
import App from './App.vue';
createApp(App).mount('#app');

index.html

<!doctype html>
<html lang="en"><head><meta charset="UTF-8"><title>Contract scenario</title></head>
<body><div id="app"></div><script type="module" src="/main.ts"></script></body></html>

App.vue

<script setup lang="ts">
import Counter from './Counter.vue';
</script>

<template>
<Counter /><Counter />
</template>

Counter.vue

<script setup lang="ts">
import { useCounter } from './use-counter';
const { count, doubled } = useCounter();
</script>

<template>
<button @click="count++">{{ count }}</button><p>{{ doubled }}</p>
</template>

Bad

Both reactive APIs run while the module loads. The two Counter instances therefore share one ref and computed value despite the intended independent counters.

use-counter.ts

import { computed, ref } from 'vue';
const count = ref(0);
const doubled = computed(() => count.value * 2);
export function useCounter() { return { count, doubled }; }

Good

useCounter creates the ref and computed synchronously inside each component setup call, giving each widget its own state and tracked derivation.

use-counter.ts

import { computed, ref } from 'vue';
export function useCounter() {
  const count = ref(0);
  const doubled = computed(() => count.value * 2);
  return { count, doubled };
}

The Good files demonstrate the change described above; other diagnostics can still apply to the complete project.

Public explanation

Cross-file index