How to add included Pug files to Vite module graph - vue.js

Question

I wrote a Rollup plugin to import Pug as an HTML string:
// Rollup plugin imported to Vite config
import { render } from 'pug';
export default function pug() {
return {
name: 'rollup-plugin-pug-html',
transform(src, id) {
if (id.endsWith('.pug')) {
const html = render(src, { filename: id });
const code = `export default ${JSON.stringify(html)};`;
return { code };
}
},
};
}
I'm using it in Vite to create templates for Vue components, as in this reduced example:
// ProofOfConceptSFC.vue
<script>
import { compile } from 'vue/dist/vue.esm-bundler.js';
import template from './template.pug';
export default {
render: compile(template)
};
</script>
The HMR is working great when I edit template.pug. The new template appears and the latest reactive values persist.
My problem is that template.pug may depend on other Pug files with include:
//- template.pug
include ./header.pug
p Hello {{ name }}
include ./footer.pug
The Vite server doesn't know about those files, and nothing happens if I touch them. Ideally I could invalidate template.pug when any Pug file is changed.
I'm guessing I want my plugin to update the ViteDevServer's server.moduleGraph. Is there a supported way to do that?

Answer 1

Huge thanks to the friendly Vite chat on Discord for setting me in the right direction.
The two keys I was missing:
Use Pug compile to create a render method that has render.dependencies, as done by Parcel
Use virtual import statements to attach the dependencies to the transform hook result, as done by vite-plugin-svelte.
Here is the working plugin:
import { compile } from 'pug';
export default function pluginPug() {
return {
name: 'vite-plugin-pug',
transform(src, id) {
if (id.endsWith('.pug')) {
const render = compile(src, { filename: id });
const html = render();
let code = '';
for (let dep of render.dependencies) {
code += `import ${JSON.stringify(dep)};\n`;
}
code += `export default ${JSON.stringify(html)};`;
return { code };
}
},
};
}