No Error on DNS/network failure about mongo-rust-driver HOT 2 CLOSED

Thanks, that makes sense!

from mongo-rust-driver.

So the reason this behaves the way that it does is that std::result::Result implements IntoIterator via an iterator over the Ok value (if any), and Collection::find returns a Result<Cursor>. What's happening here is that collection.find is returning Err(<a server selection error>) so the for in loop doesn't execute its body because there are no Ok values to iterate over. If you replace the for in loop with collection.find(doc! {}, None).await.unrwrap() you should see the error.

Note that async for in loops aren't yet a part of the language, so you'll need to use a while loop in conjunction with the methods provided by StreamExt / TryStreamExt to iterate over cursors, like so:

use mongodb::{Client, Collection};
use mongodb::bson::{doc, Document};
use futures::stream::TryStreamExt;

#[tokio::main]
async fn main() {
    let client = Client::with_uri_str("mongodb://obvious_garbage/?serverSelectionTimeoutMS=1000").await.unwrap();
    let db = client.database("");
    let collection: Collection<Document> = db.collection("");
    let mut cursor = collection.find(doc! {}, None).await.unwrap();
    while let Some(doc) = cursor.try_next().await.unwrap() {
        println!("{:?}", doc);
    }
}

Hope that makes sense; please let us know if you have any further questions!

from mongo-rust-driver.