kuzzle/no-then #

Enforce async/await syntax over Promise chains.

Rationale #

.then() / .catch() chains and async/await express the same thing, and mixing both in one codebase makes control flow harder to follow: a .catch() attached below an await does not catch what a reader expects, and a forgotten return inside a .then() silently swallows the rest of the chain.

Kuzzle backend code is async/await throughout. This rule keeps it that way.

Incorrect #

function loadUser(id) {
  return sdk.document
    .get('app', 'users', id)
    .then((user) => enrich(user))
    .catch((error) => {
      context.log.error(error);
      throw error;
    });
}

Correct #

async function loadUser(id) {
  try {
    const user = await sdk.document.get('app', 'users', id);

    return enrich(user);
  } catch (error) {
    context.log.error(error);
    throw error;
  }
}

Enabling #

// eslint.config.mjs
import kuzzle from 'eslint-plugin-kuzzle';

export default [
  ...kuzzle.configs.default,
  ...kuzzle.configs.node,
  {
    rules: {
      'kuzzle/no-then': 'warn',
    },
  },
];

Start at warn, see what it reports on your codebase, then promote it to error.

Known limitation #

The rule matches any member expression named then or catch, without checking that the receiver is a Promise. A try { … } catch (error) { … } statement is fine — that is not a member expression — but these are all reported:

• emitter.catch, or a domain object that happens to expose a .then() method;
• a then property on a plain object or a mock;
• the places where a chain is genuinely clearer, such as a deliberate fire-and-forget .catch(context.log.error) on a promise you do not await.

Silence those inline:

// eslint-disable-next-line kuzzle/no-then -- deliberate fire-and-forget
refreshCache().catch(context.log.error);

Configuration #

The rule takes no options. The two messages it reports are Prefer async/await to Promise.then() and Prefer async/await to Promise.catch().