Vue 2 Installation

Install markstream-vue2 with pnpm, npm or yarn.

pnpm add markstream-vue2
# or
npm install markstream-vue2
# or
yarn add markstream-vue2

Requirements

markstream-vue2 requires:

• Vue 2.6.14+ (Vue 2.7 is recommended for better TypeScript support)
• @vue/composition-api (if using Vue 2.6.x)

Composition API compatibility (Vue 2.6 / 2.7 / 3.x)

Vue version	Composition API availability	What to install	How to import
2.6.x	Not built-in	@vue/composition-api	import { ref, computed, defineComponent } from '@vue/composition-api'
2.7.x	Built-in	None	import { ref, computed, defineComponent } from 'vue'
3.x	Built-in	None	import { ref, computed, defineComponent } from 'vue'

Notes:

• For Vue 2.6.x, you must install and register the plugin (Vue.use(@vue/composition-api)), otherwise you will get runtime errors.
• For Vue 2.7.x, do not install @vue/composition-api — it is already included in Vue 2.7.
• For Vue 3.x, use markstream-vue (not markstream-vue2).

Quick start by version (dependencies + entry)

Vue 2.6.x

Dependencies:

pnpm add markstream-vue2 vue@2.6.14 vue-template-compiler@2.6.14 @vue/composition-api

App entry:

import VueCompositionAPI from '@vue/composition-api'
import MarkdownRender, { VueRendererMarkdown } from 'markstream-vue2'
import Vue from 'vue'
import 'markstream-vue2/index.css'

Vue.use(VueCompositionAPI)
Vue.use(VueRendererMarkdown)

new Vue({
  render: h => h(MarkdownRender, { props: { content: '# Vue 2.6' } }),
}).$mount('#app')

Composition API usage in components:

import { defineComponent, ref } from '@vue/composition-api'

Example in this repo:

• playground-vue2-cli (Vue 2.6 + Vue CLI / Webpack 4)

Path and start command:

pnpm -C playground-vue2-cli dev

From repo root you can also run:

pnpm play:vue2-cli

Vue 2.7.x

Dependencies:

pnpm add markstream-vue2 vue@2.7.16 vue-template-compiler@2.7.16

App entry:

import MarkdownRender, { VueRendererMarkdown } from 'markstream-vue2'
import Vue from 'vue'
import 'markstream-vue2/index.css'

Vue.use(VueRendererMarkdown)

new Vue({
  render: h => h(MarkdownRender, { props: { content: '# Vue 2.7' } }),
}).$mount('#app')

Composition API usage in components:

import { defineComponent, ref } from 'vue'

Example in this repo:

• playground-vue2 (Vue 2.7 + Vite)

Path and start command:

pnpm -C playground-vue2 dev

From repo root you can also run:

pnpm play:vue2

Vue 3.x (use markstream-vue)

Dependencies:

pnpm add markstream-vue vue@^3

App entry:

import MarkdownRender from 'markstream-vue'
import { createApp, h } from 'vue'
import 'markstream-vue/index.css'

createApp({
  render: () => h(MarkdownRender, { content: '# Vue 3' }),
}).mount('#app')

If your workspace also installs Vue 3, make sure vue-demi targets Vue 2:

pnpm vue-demi-switch 2

If you cannot run vue-demi-switch (or want a per-app fix), alias vue-demi to the Vue 2 build in your bundler config. This avoids errors like defineComponent is not a function:

// vue.config.js / webpack config
module.exports = {
  configureWebpack: {
    resolve: {
      alias: {
        'vue-demi$': 'vue-demi/lib/v2/index.cjs',
      },
    },
  },
}

Optional Peer Dependencies

markstream-vue2 supports various features through optional peer dependencies. Install only what you need:

Feature	Required Packages	Install Command
Shiki code blocks (MarkdownCodeBlockNode)	shiki, stream-markdown	pnpm add shiki stream-markdown
Monaco Editor (full code block features)	stream-monaco	pnpm add stream-monaco
Mermaid Diagrams	mermaid	pnpm add mermaid
D2 Diagrams	@terrastruct/d2	pnpm add @terrastruct/d2
Math Rendering (KaTeX)	katex	pnpm add katex

Vue 2.6.x Setup

If you're using Vue 2.6.x, you need to install and configure @vue/composition-api:

pnpm add @vue/composition-api

Then in your app entry:

import VueCompositionAPI from '@vue/composition-api'
import Vue from 'vue'

Vue.use(VueCompositionAPI)

Using Composition API in Vue 2.6 components:

import { defineComponent, ref } from '@vue/composition-api'

Vue 2.7.x Setup (no plugin required)

Vue 2.7 has Composition API built-in. Do not install @vue/composition-api.

import { defineComponent, ref } from 'vue'

Feature loaders (Mermaid / KaTeX / D2)

After installing optional peers, the default loaders are already enabled. Only call these helpers if you disabled them earlier or need a custom loader (for example, a CDN build):

import { enableD2, enableKatex, enableMermaid } from 'markstream-vue2'

// optional: re-enable or override loaders
enableMermaid()
enableKatex()
enableD2()

Also remember required CSS (when the feature is used):

import 'markstream-vue2/index.css'
import 'katex/dist/katex.min.css'

Monaco (stream-monaco) does not require a separate CSS import.

Note: markstream-vue2/index.css is scoped under an internal .markstream-vue2 container to reduce global style conflicts. MarkdownRender renders inside that container by default. If you render node components standalone, wrap them with <div class="markstream-vue2">...</div>.

Vue CLI (Webpack 4) Notes

Vue CLI 4 uses Webpack 4 by default, and Webpack 4 doesn't support package.json#exports. That commonly breaks:

• import 'markstream-vue2/index.css'
• import('mermaid')
• Vite-style worker imports: ?worker / ?worker&inline

Recommended setup (see playground-vue2-cli):

1. Import CSS via the real file path (no exports needed):

import 'markstream-vue2/dist/index.css'

2. For Mermaid, prefer the CDN global build (avoids Webpack 4 exports / ESM chains):

<!-- public/index.html -->
<script src="https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.min.js"></script>

3. For KaTeX / Mermaid workers, prefer CDN workers to avoid Webpack 4 worker limitations:

import { createKaTeXWorkerFromCDN, createMermaidWorkerFromCDN, setKaTeXWorker, setMermaidWorker } from 'markstream-vue2'

const { worker: katexWorker } = createKaTeXWorkerFromCDN({
  mode: 'classic',
  katexUrl: 'https://cdn.jsdelivr.net/npm/katex@0.16.25/dist/katex.min.js',
  mhchemUrl: 'https://cdn.jsdelivr.net/npm/katex@0.16.25/dist/contrib/mhchem.min.js',
})
if (katexWorker)
  setKaTeXWorker(katexWorker)

const { worker: mermaidWorker } = createMermaidWorkerFromCDN({
  mode: 'classic',
  mermaidUrl: 'https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.min.js',
})
if (mermaidWorker)
  setMermaidWorker(mermaidWorker)

If you want to keep using subpath imports like markstream-vue2/index.css, add resolve.alias mappings in vue.config.js (see playground-vue2-cli/vue.config.js).

Code blocks: prefer stream-markdown override

In Webpack 4, Monaco integration (stream-monaco) is prone to edge cases (worker resolution, ESM entrypoints, service registration, and Shiki/TextMate regex engine init issues). If your goal is “render code blocks with highlighting”, the most reliable approach is:

1. Install Shiki renderer deps:

pnpm add shiki stream-markdown

2. Override code_block to use MarkdownCodeBlockNode (or your own component):

import { MarkdownCodeBlockNode, setCustomComponents } from 'markstream-vue2'

setCustomComponents({ code_block: MarkdownCodeBlockNode })

3. Webpack config pitfalls:

• If you use webpack.IgnorePlugin for optional dependencies, ensure stream-markdown is not ignored.
• stream-markdown is ESM-only. In a CJS vue.config.js, require.resolve('stream-markdown') can fail even when installed. Use a filesystem fallback (check node_modules/stream-markdown) and alias it to dist/index.js. See playground-vue2-cli/vue.config.js.

If you're in a monorepo/workspace (common with pnpm), make sure your app uses a single Vue 2 runtime instance. Otherwise you may see runtime warnings like: provide() can only be used inside setup() / onMounted is called when there is no active component instance (caused by duplicated Vue copies and mismatched Composition API context). Fix this by pinning vue$ to your project's Vue 2 runtime in Webpack (see playground-vue2-cli/vue.config.js).

Tailwind CSS Support

If your app uses Tailwind and you want to avoid duplicate utility CSS, import the Tailwind-ready output instead:

import 'markstream-vue2/index.tailwind.css'

And include the extracted class list in tailwind.config.js:

module.exports = {
  content: [
    './src/**/*.{js,ts,vue}',
    require('markstream-vue2/tailwind'),
  ],
}

This approach ensures that Tailwind includes all the utility classes used by markstream-vue2 in its purge process, resulting in a smaller final bundle size.

Troubleshooting (Common Runtime Errors)

defineComponent is not a function

Cause: vue-demi is in Vue 3 mode but the app runs Vue 2.x. Fix (pick one):

• Run pnpm vue-demi-switch 2.
• Or alias vue-demi$ to vue-demi/lib/v2/index.cjs in your bundler config (see above).

provide() can only be used inside setup() / onMounted is called when there is no active component instance

Cause: duplicate Vue 2 runtime instances in monorepo/pnpm workspace. Fix: ensure a single Vue 2 instance is used across the app and linked packages:

• Alias vue$ to your app's Vue 2 runtime (see playground-vue2-cli/vue.config.js).
• In pnpm workspaces, add overrides for playground-vue2-cli>vue to pin Vue 2.

Vue packages version mismatch

Cause: vue and vue-template-compiler versions differ. Fix: align them (e.g. both 2.6.14 or both 2.7.16). In pnpm, you can use packageExtensions or overrides.

Cannot read properties of undefined (reading 'props')

Cause: Vue 2.6 + Composition API missing _setupProxy patch, or Composition API not installed. Fix:

• Ensure @vue/composition-api is installed and Vue.use(VueCompositionAPI) is executed before using markstream-vue2.
• Upgrade to the latest markstream-vue2 build in this repo (it patches _setupProxy for Vue 2.6).

Quick Install: All Features

To enable all features at once:

pnpm add shiki stream-markdown stream-monaco mermaid @terrastruct/d2 katex
# or
npm install shiki stream-markdown stream-monaco mermaid @terrastruct/d2 katex

Feature Details

Code Syntax Highlighting

Requires both shiki and stream-markdown:

pnpm add shiki stream-markdown

These packages power the Shiki-based MarkdownCodeBlockNode. To use Shiki inside MarkdownRender, override the code_block renderer (or render MarkdownCodeBlockNode directly).

import MarkdownRender, { MarkdownCodeBlockNode, setCustomComponents } from 'markstream-vue2'

setCustomComponents({ code_block: MarkdownCodeBlockNode })

Monaco Editor

For full code block functionality (copy button, font size controls, expand/collapse):

pnpm add stream-monaco

Without stream-monaco, code blocks will render but interactive buttons may not work.

Mermaid Diagrams

For rendering Mermaid diagrams:

pnpm add mermaid

D2 Diagrams

For rendering D2 diagrams:

pnpm add @terrastruct/d2

KaTeX Math Rendering

For math formula rendering:

pnpm add katex

Also import the KaTeX CSS in your app entry:

import 'katex/dist/katex.min.css'

Quick Test

Import and render a simple markdown string:

<script>
import MarkdownRender from 'markstream-vue2'
import 'markstream-vue2/index.css'

export default {
  components: {
    MarkdownRender
  },
  data() {
    return {
      md: '# Hello from markstream-vue2!'
    }
  }
}
</script>

<template>
  <MarkdownRender :content="md" />
</template>

Using with Composition API (Vue 2.7+)

If you're using Vue 2.7 or have @vue/composition-api installed:

<script>
import { defineComponent, ref } from '@vue/composition-api' // or 'vue' for 2.7
import MarkdownRender from 'markstream-vue2'
import 'markstream-vue2/index.css'

export default defineComponent({
  components: {
    MarkdownRender
  },
  setup() {
    const md = ref('# Hello from markstream-vue2 with Composition API!')
    return { md }
  }
})
</script>

<template>
  <MarkdownRender :content="md" />
</template>

TypeScript Support

markstream-vue2 includes TypeScript definitions. For Vue 2.6.x, you may need to configure your tsconfig.json:

{
  "compilerOptions": {
    "types": ["@vue/composition-api"]
  }
}

For Vue 2.7+, types are included automatically.