No Sync Fn In Async Fn - Denoland

Disallow sync function inside async function.

Using sync functions like Deno.readTextFileSync blocks the deno event loop so it's not recommended to use it inside of an async function, because it stops progress of all other async tasks.

Invalid:

javascript

async function foo() {
  Deno.readTextFileSync("");
}

const fooFn = async function foo() {
  Deno.readTextFileSync("");
};

const fooFn = async () => {
  Deno.readTextFileSync("");
};

Valid:

javascript

async function foo() {
  await Deno.readTextFile("");
}

function foo() {
  Deno.readTextFileSync("");
}

const fooFn = function foo() {
  Deno.readTextFileSync("");
};

const fooFn = () => {
  Deno.readTextFileSync("");
};