return-await.md

return-await

Enforces consistent returning of awaited values.

Returning an awaited promise can make sense for better stack trace information as well as for consistent error handling (returned promises will not be caught in an async function try/catch).

Rule Details

This rule builds on top of the eslint/no-return-await rule. It expands upon the base rule to add support for optionally requiring return await in certain cases.

How to Use

{
  // note you must disable the base rule as it can report incorrect errors
  "no-return-await": "off",
  "@typescript-eslint/return-await": "error"
}

Options

type Options = 'in-try-catch' | 'always' | 'never';

const defaultOptions: Options = 'in-try-catch';

in-try-catch

Requires that a returned promise must be awaited in try-catch-finally blocks, and disallows it elsewhere. Specifically:

• if you return a promise within a try, then it must be awaited.
• if you return a promise within a catch, and there is no finally, then it must not be awaited.
• if you return a promise within a catch, and there is a finally, then it must be awaited.
• if you return a promise within a finally, then it must not be awaited.

Examples of code with in-try-catch:

❌ Incorrect

async function invalidInTryCatch1() {
  try {
    return Promise.resolve('try');
  } catch (e) {}
}

async function invalidInTryCatch2() {
  try {
    throw new Error('error');
  } catch (e) {
    return await Promise.resolve('catch');
  }
}

async function invalidInTryCatch3() {
  try {
    throw new Error('error');
  } catch (e) {
    return Promise.resolve('catch');
  } finally {
    console.log('cleanup');
  }
}

async function invalidInTryCatch4() {
  try {
    throw new Error('error');
  } catch (e) {
    throw new Error('error2');
  } finally {
    return await Promise.resolve('finally');
  }
}

async function invalidInTryCatch5() {
  return await Promise.resolve('try');
}

async function invalidInTryCatch6() {
  return await 'value';
}

✅ Correct

async function validInTryCatch1() {
  try {
    return await Promise.resolve('try');
  } catch (e) {}
}

async function validInTryCatch2() {
  try {
    throw new Error('error');
  } catch (e) {
    return Promise.resolve('catch');
  }
}

async function validInTryCatch3() {
  try {
    throw new Error('error');
  } catch (e) {
    return await Promise.resolve('catch');
  } finally {
    console.log('cleanup');
  }
}

async function validInTryCatch4() {
  try {
    throw new Error('error');
  } catch (e) {
    throw new Error('error2');
  } finally {
    return Promise.resolve('finally');
  }
}

async function validInTryCatch5() {
  return Promise.resolve('try');
}

async function validInTryCatch6() {
  return 'value';
}

always

Requires that all returned promises are awaited.

Examples of code with always:

❌ Incorrect

async function invalidAlways1() {
  try {
    return Promise.resolve('try');
  } catch (e) {}
}

async function invalidAlways2() {
  return Promise.resolve('try');
}

async function invalidAlways3() {
  return await 'value';
}

✅ Correct

async function validAlways1() {
  try {
    return await Promise.resolve('try');
  } catch (e) {}
}

async function validAlways2() {
  return await Promise.resolve('try');
}

async function validAlways3() {
  return 'value';
}

never

Disallows all awaiting any returned promises.

Examples of code with never:

❌ Incorrect

async function invalidNever1() {
  try {
    return await Promise.resolve('try');
  } catch (e) {}
}

async function invalidNever2() {
  return await Promise.resolve('try');
}

async function invalidNever3() {
  return await 'value';
}

✅ Correct

async function validNever1() {
  try {
    return Promise.resolve('try');
  } catch (e) {}
}

async function validNever2() {
  return Promise.resolve('try');
}

async function validNever3() {
  return 'value';
}

Attributes

• ✅ Recommended
• 🔧 Fixable
• 💭 Requires type information