using ua->get_p in an async helper

[michaelfung]

The only way I can find to get rid of the "Unhandled rejected promise: ..." warning when using an async helper is to use catch:

helper get_site_title => async sub {
  my ($c, $url) = @_;
  my ($tx, $err);
  eval { $tx = await $c->ua->get_p($url)->catch( sub { ($err) = @_; });};
  die "$err" if $err;
  my $result = $tx->result;
  die $result->message if $result->is_error;
  die 'unknown error condition' unless $result->is_success;
  return $result->dom->at('title')->text;
};

Are there any better alternatives?

Edit: a test case to demo the issue:
https://gist.github.com/michaelfung/0ab0624f53d3f5b101e677276179b6ba

[yuki-kimoto]

Thank you for posting.

Sorry, I don't know async/await syntax yet.

[kraih]

Every await throws an exception, like a normal blocking operation. They bubble up through the stack and will need to be caught somewhere. That is exactly how it's supposed to work. Either you add a catch handler to the outermost promise, or you try/catch the thrown exception.

[michaelfung]

For the record, now I resort to:

$app->helper('get_title' => sub($c,$url) {
    return $c->ua->get_p($url)->then(sub ($tx) {
        my $result = $tx->result;
        die $result->message if $result->is_error;
        die 'unknown error condition' unless $result->is_success;
        $result->dom->at('title') or die "no title";
        return $result->dom->at('title')->text;
    });
});

async sub title($c) {
    my $tx = $c->render_later->tx;
    my $url = $c->param('url');
    my $title;
    try {
        $title = await $c->get_title($url);
    } catch ($e) {
        # process $e
    }
    unless ($title) {
        $c->render(text => "error fetching title for $url");
        return;
    }
    # continue process title ...
    $c->render(text => "processed result for $title is ...");
}