cofin/vue

Vue 3 Framework Skill

<workflow>

Quick Reference

Composition API Component

<example>

<script setup lang="ts">
import { ref, computed, onMounted } from 'vue';

interface Props {
  title: string;
  items: Item[];
}

const props = defineProps<Props>();
const emit = defineEmits<{
  select: [item: Item];
}>();

const selected = ref<Item | null>(null);
const count = computed(() => props.items.length);

function handleSelect(item: Item) {
  selected.value = item;
  emit('select', item);
}

onMounted(() => {
  console.log('Component mounted');
});
</script>

<template>
  <div>
    <h2>{{ title }} ({{ count }})</h2>
    <ul>
      <li
        v-for="item in items"
        :key="item.id"
        @click="handleSelect(item)"
      >
        {{ item.name }}
      </li>
    </ul>
  </div>
</template>

</example>

Composables

<example>

// composables/useFetch.ts
import { ref, watchEffect, type Ref } from 'vue';

export function useFetch<T>(url: Ref<string> | string) {
  const data = ref<T | null>(null) as Ref<T | null>;
  const loading = ref(true);
  const error = ref<Error | null>(null);

  watchEffect(async () => {
    loading.value = true;
    error.value = null;

    try {
      const urlValue = typeof url === 'string' ? url : url.value;
      const res = await fetch(urlValue);
      if (!res.ok) throw new Error(`HTTP ${res.status}`);
      data.value = await res.json();
    } catch (e) {
      error.value = e instanceof Error ? e : new Error(String(e));
    } finally {
      loading.value = false;
    }
  });

  return { data, loading, error };
}

</example>

Provide/Inject Pattern

<example>

// context/theme.ts
import { provide, inject, ref, type InjectionKey, type Ref } from 'vue';

type Theme = 'light' | 'dark';
const ThemeKey: InjectionKey<{
  theme: Ref<Theme>;
  toggle: () => void;
}> = Symbol('theme');

export function provideTheme() {
  const theme = ref<Theme>('light');
  const toggle = () => {
    theme.value = theme.value === 'light' ? 'dark' : 'light';
  };
  provide(ThemeKey, { theme, toggle });
}

export function useTheme() {
  const context = inject(ThemeKey);
  if (!context) throw new Error('useTheme requires ThemeProvider');
  return context;
}

</example>

v-model with Components

<example>

<script setup lang="ts">
const model = defineModel<string>({ required: true });

// Or with options
const count = defineModel<number>('count', { default: 0 });
</script>

<template>
  <input v-model="model" />
</template>

</example>

Async Components

<example>

import { defineAsyncComponent } from 'vue';

const AsyncModal = defineAsyncComponent({
  loader: () => import('./Modal.vue'),
  loadingComponent: LoadingSpinner,
  delay: 200,
  errorComponent: ErrorDisplay,
});

</example> </workflow>

Best Practices

• Use <script setup> for cleaner syntax
• Prefer Composition API over Options API
• Use TypeScript with defineProps<T>() and defineEmits<T>()
• Extract reusable logic into composables
• Use shallowRef for large objects that don't need deep reactivity
• Avoid mutating props directly

References Index

• Litestar-Vite Integration — Backend integration with Litestar-Vite plugin.

Deployment

Build Production

Vue applications are built into static assets using Vite.

vite build

Strategy

Deploy to static runners or reverse proxies. For Inertia apps, bundle assets inside the backend build directory for joint deployment.

---

CI/CD Actions

<example>

Example GitHub Actions workflow for building:

name: Vue CI
on: [push, pull_request]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Setup Node
        uses: actions/setup-node@v4
        with:
          node-version: '22'
          cache: 'npm'

      - run: npm ci
      - run: npm run build

</example>

Official References

• https://vuejs.org/guide/introduction.html
• https://vuejs.org/guide/typescript/overview.html
• https://vuejs.org/guide/components/v-model.html
• https://github.com/vuejs/core/releases
• https://vite.dev/guide/
• https://inertiajs.com/docs/v2/installation/client-side-setup

Shared Styleguide Baseline

• Use shared styleguides for generic language/framework rules to reduce duplication in this skill.
• General Principles
• Vue
• TypeScript
• Keep this skill focused on tool-specific workflows, edge cases, and integration details.

<guardrails> ## Guardrails

• Always use <script setup> with TypeScript -- This is the modern standard for Vue 3; provides better IDE support and less boilerplate.
• Never mutate props directly -- Props are read-only; use emit to notify the parent of changes or use computed with a setter.
• Prefer Composables for shared logic -- Avoid Mixins or global state; extract logic into reusable use* functions to keep components focused on UI.
• Use defineProps and defineEmits macros -- These are compiler macros; do not import them. Use the type-based declaration for best DX.
• Avoid direct DOM manipulation -- Use ref for DOM elements only when necessary; prefer Vue's declarative directives (v-bind, v-if, v-for). </guardrails>

<validation> ## Validation Checkpoint

• [ ] Component uses <script setup lang="ts">
• [ ] Props and Emits are defined using type-based declarations (defineProps<T>())
• [ ] No direct mutations of props are present
• [ ] Reusable logic is extracted into a composable if it exceeds 30-40 lines
• [ ] v-for elements have a unique and stable :key
• [ ] No direct DOM manipulation (e.g., document.querySelector) is used where Vue directives suffice </validation>