How to use assert within async functions? (Typescript)

Question

I have a block like below, which is a function using async If I add an assert statement in there, it will stop the code executing at that line, but no error is thrown. It just dies silently :(

async function testMongo() {
  let db = await dbConnect();

  await db.collection("stories").remove({});
  let c = await count("stories", {} );
  assert.strictEqual(c, 999);   // should fail
  console.log("moving on...");  /// will never get reached.

}

Is there some reason that the assertion maybe gets swallowed up? I've had problems like these before with errors inside event emitters, and it seems the immediate return of the async function is some type of event emitter/Promise.

Amid · Accepted Answer · 2016-03-02 13:29:55Z

1

console.log() call can be skipped is if async db.connection() or count() will reject their promises. It this case your should try wrapping those calls in try/catch:

try
{
    await db.collection("stories").remove({});
}
catch(e)
{
    //...    
}

Or catch error using promise:

await db.collection("stories").remove({}).catch((e) => {//...});

[EDIT]

The generic wrapper that will execute async function and continue even on rejection can look something like this:

async function Do<T>(func: ()=>Promise<T>)
{
    try
    {
        await func();
    }
    catch(e)
    {
        console.log(e);  
    }
}

edited Mar 2, 2016 at 13:29

answered Mar 2, 2016 at 7:57

Amid

22.5k6 gold badges63 silver badges59 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

dcsan Over a year ago

i wonder if there's a way to push than into a generic wrapper for all awaited functions?

Collectives™ on Stack Overflow

How to use assert within async functions? (Typescript)

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related