Using jest with files with glob imports

Question

I utilize webpack with webpack-import-glob-loader to import files using glob pattern. So in one of my files (src/store/resources/module.ts) I have a line:

import '../../modules/resources/providers/**/*.resource.ts';

When I run a test with ts-jest it fails and reports the following message:

Cannot find module '../../modules/resources/providers/**/*.resource.ts' from 'src/store/resources/module.ts`

I assume it complains because it can't recognize this import syntax.

How to make jest work for project with glob imports?

Answer 1

I solved this by manually handling the globs inside of a jest preprocessor. Since you need to control processing of the files to handle globs in this approach, you have to manually initialize your processor.

// config.js
module.exports = {
  transform: {
    '.': `./path/to/your/processor.js`

// processor.js
const path = require(`path`);
const glob = require(`glob`).sync;
const yourProcessor = // require your processor code - ts-jest, babel-jest, esbuild-jest, etc

module.exports = {
  process(src, filename, config, opts) {
    const dir = path.dirname(filename);
    src = processGlob(src, dir);
    return yourProcessor(src, filename, config, opts);
  },
};

function processGlob(src, dir) {
  // This will match things like
  //   import './**/*';
  //   import '../../modules/resources/providers/**/*.resource.ts';
  // Takes inspiration from https://github.com/excid3/esbuild-rails/blob/main/src/index.js
  return src.replace(/^import\s'(.*\*.*)';$/m, (_match, pathCapture) => {
    const matcher = /.+\..+/; // Handles '.' results
    const files = glob(pathCapture, {
      cwd: dir,
    })
      .sort()
      .filter((path) => matcher.test(path));

    return `${files.map((module, index) => `import * as module${index} from '${module}'`).join(`;`)}`;
  });
}

In this approach you can only glob once per file (because it uses the .map indexes to add numbers to each import module name). You could keep track of a global count variable instead, if you wanted to have several glob imports in one file.