Custom loaders

[amulchinock]

This library assumes that developers will have their entry files in the same directory as their source NJK files.

We have a need to support passing options to nunjucks.FileSystemLoader(), which is currently not possible.

https://mozilla.github.io/nunjucks/api.html#filesystemloader

[amulchinock]

A quick suggested change would be (untested):

function NunjucksPlugin({
  input,
  output,
  vars = {},
  opts = {},
  preRenderEnvironment,
  loaders = [] // adds ability to pass in an array of loaders
} = {}) {

   if (!input) throw new Error('no input file specified');
   if (!output) throw new Error('no output file specified');
  
  const handleTemplateContent = async (templateContent, bundlePath) => {
    nunjucks.configure(opts);
    const environment = new nunjucks.Environment(loaders.length > 0 ? loaders : null); // pass the loaders to nunjucks
    if (preRenderEnvironment) preRenderEnvironment(environment);
    const rendered = environment.renderString(templateContent, {
      ...vars,
      bundlePath
    });

    const actualPathOut = actualPath(output);
    await fs.promises.writeFile(actualPathOut, rendered);
  };

  return {
    name: PLUGIN_NAME,
    async buildStart() {
      this.addWatchFile(actualPath(input));
    },
    async writeBundle(bundle) {
      const { file: bundlePath } = bundle;

      const actualPathIn = actualPath(input);
      const templateContent = await fs.promises.readFile(actualPathIn, 'utf-8');
      await handleTemplateContent(templateContent, bundlePath);
    }
  };
}

To use it:

import nunjucks from 'nunjucks';

export default {
  plugins: [
    NunjucksPlugin({
      input: 'whatever.html',
      output: 'whatever.html',
      loaders: [
        new nunjucks.FileSystemLoader('some/directory')
      ]
    })
  ]
}