Requires any function or method that returns a Promise to be marked async (promise-function-async)

Requires any function or method that returns a Promise to be marked async. Ensures that each function is only capable of:

• returning a rejected promise, or
• throwing an Error object.

In contrast, non-async Promise - returning functions are technically capable of either. Code that handles the results of those functions will often need to handle both cases, which can get complex. This rule's practice removes a requirement for creating code to handle both cases.

Rule Details

Examples of code for this rule

❌ Incorrect

const arrowFunctionReturnsPromise = () => Promise.resolve('value');

function functionReturnsPromise() {
  return Promise.resolve('value');
}

✅ Correct

const arrowFunctionReturnsPromise = async () => Promise.resolve('value');

async function functionReturnsPromise() {
  return Promise.resolve('value');
}

Options

Options may be provided as an object with:

• allowAny to indicate that any or unknown shouldn't be considered Promises (true by default).
• allowedPromiseNames to indicate any extra names of classes or interfaces to be considered Promises when returned.

In addition, each of the following properties may be provided, and default to true:

• checkArrowFunctions
• checkFunctionDeclarations
• checkFunctionExpressions
• checkMethodDeclarations

{
  "@typescript-eslint/promise-function-async": [
    "error",
    {
      "allowedPromiseNames": ["Thenable"],
      "checkArrowFunctions": true,
      "checkFunctionDeclarations": true,
      "checkFunctionExpressions": true,
      "checkMethodDeclarations": true
    }
  ]
}

Related To

• TSLint: promise-function-async

Attributes

• ✅ Recommended
• 🔧 Fixable
• 💭 Requires type information