rollup plugin for wrapping a JSON file in a module with a default export only. This avoids the issue of fields being invalid names.

json.js

// An as-simple-as-possible JSON plugin for rollup. This plugin turns a JSON
// file into a module with a default export. No named exports are given since
// field names are not always valid names.

// Originally drawn from the official JSON plugin.

function buildAst(code) {
  return {
    type: 'Program',
    sourceType: 'module',
    start: 0,
    end: code.length,
    body: [
      {
        type: 'ExportDefaultDeclaration',
        start: 0,
        end: code.length,
        declaration: {
          type: 'Literal',
          start: 15,
          end: code.length - 1,
          value: null,
          raw: 'null'
        }
      }
    ]
  };
}

function transform(untrimmed, id) {
  if (!id.endsWith('.json')) {
    return null;
  }

  // Trim leading and trailing whitespace.
  const json = untrimmed.replace(/^\s+|\s+$/g, '');

  // Ensure JSON parses.
  JSON.parse(json);

  const code = `export default ${json};`;
  const ast = buildAst(code);

  return { ast, code, map: { mappings: '' } };
}

module.exports = function json() {
  return { name: 'json', transform };
};