allthewaypromises.pl

Controller::method {
    my $promise = Utils::get_me_promise;
    return $promise->then(sub ($inner_promise) {
        say 'method outer resolved';
        return $inner_promise->then(sub ($something) {
            say 'method inner resolved';
            render $something;
        }, sub {
            log_error
        }
    }, sub {
        log_error
    });
}

Utils::get_me_promise {
    my @promises;
    for (...) {
        push @promises, $ua->post_p->then(sub ($tx) {
            return _get_data_from($tx)
        });
    }
    # @promises always non empty
    
    return Mojo::Promise->all(@promises)->then(sub (@data) {
        say 'get_me_promise resolved';
        return Utils::_get_inner_promise(@data)
    });
}

Utils::_get_inner_promise (@data) {
    my @promises;
    for (...) {
        ...
    }
    # @promises could be empty
    
    my $promise = @promises ? Mojo::Promise->all(@promises) : Mojo::Promise->new->resolve;
    return $promise->then(sub {
        say '_get_inner_promise resolved';
        return something-that-should-return-to-controller-method;
    });
}

# so, when @promises in _get_inner_promise empty, I get:
# get_me_promise resolved
# _get_inner_promise resolved
# method outer resolved

# I expect:
# get_me_promise resolved
# method outer resolved
# _get_inner_promise resolved
# method inner resolved