dataloader-error-progagation.ts

import DataLoader from 'dataloader';

async function main() {
  const loader = new DataLoader(
    // eslint-disable-next-line require-await
    async (keys: readonly string[]) => {
      const results = keys.map(key => {
        if (key === 'return error') {
          return new Error('"returned error"');
        } else if (key === 'throw error') {
          throw new Error('"thrown error"');
        } else {
          return `Ok: ${key}`;
        }
      });
      return results;
    },
    { cache: false },
  );

  console.log('loadOneOkValue');
  const loadOneOkValue = await loader.load('1');
  console.log(loadOneOkValue);

  console.log('\n-------------\n');

  console.log('loadManyOkValue');
  const loadManyOkValue = await loader.loadMany(['1', '2', '3']);
  console.log(loadManyOkValue);

  console.log('\n-------------\n');

  console.log('loadOkAndError');
  const loadOkAndError = await loader.loadMany(['1', 'return error', '2']);
  console.log(loadOkAndError);

  console.log('\n-------------\n');

  try {
    console.log('loadOneError');
    const loadOneError = await loader.load('return error');
    console.log(loadOneError);
  } catch (error) {
    console.log('it threw', error);
  }

  console.log('\n-------------\n');

  try {
    console.log('loadOneErrorWhereLoaderThrows');
    const loadOneErrorWhereLoaderThrows = await loader.load('throw error');
    console.log(loadOneErrorWhereLoaderThrows);
  } catch (error) {
    console.log('it threw', error);
  }

  console.log('\n-------------\n');

  try {
    console.log('loadManyWhereLoaderThrows');
    const loadManyWhereLoaderThrows = await loader.loadMany([
      '1',
      'throw error',
      '2',
    ]);
    console.log(loadManyWhereLoaderThrows);
  } catch (error) {
    console.log('it threw', error);
  }
}

main();