Using the assert statement in asynchronous functions in TypeScript

Question

Using the assert statement in asynchronous functions in TypeScript

I have a block of code similar to the following, which contains a function utilizing async. Whenever I insert an assert statement within this function, it causes the code execution to halt at that specific line without throwing any errors. It simply stops in its tracks.

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.

}

I am perplexed as to why the assertion might be disappearing. This issue reminds me of previous instances where errors got lost within event emitters. It appears that the immediate return of the async function behaves akin to some sort of event emitter or Promise.

typescript async-await assert

Answer 1

Answer №1

To avoid skipping a console.log() call, ensure that async db.connection() or count() will not reject their promises. In the event of rejection, it is recommended to wrap those calls in try/catch blocks:

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

An alternative method is to catch errors using promises:

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

[UPDATE]

A versatile wrapper for executing asynchronous functions and handling rejections can be implemented like this:

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

Answer 2

To avoid skipping a console.log() call, ensure that async db.connection() or count() will not reject their promises. In the event of rejection, it is recommended to wrap those calls in try/catch blocks:

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

An alternative method is to catch errors using promises:

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

[UPDATE]

A versatile wrapper for executing asynchronous functions and handling rejections can be implemented like this:

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

Using the assert statement in asynchronous functions in TypeScript

Answer №1

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