Function local ownership where references are required - elasticsearch

Question

I am currently trying to build a request to ElasticSearch using the elasticsearch dependency.
Below, find the simplified version of the code I have written:
fn test<'a>(client: &'a Elasticsearch) -> BoxFuture<'a, std::result::Result<Bytes, elasticsearch::Error>> {
let index_parts = ["foo", "bar"]; // Imagine this list being computed and not literal
let search_response = client
.search(SearchParts::Index(&index_parts))
.from(0)
.size(1000)
.body(json!(
{ "query": { "match_all": { } } }
))
.send();
search_response
.and_then(|resp| resp.bytes())
.boxed()
}
The error I get:
cannot return value referencing local variable index_parts
returns a value referencing data owned by the current function
I totally understand why I get this error - I create a new array inside of test, but SearchParts::Index expects only a &'b [&'b str], so I have no way of giving ownership to it. So I am stuck with it.
Of course there are a couple of simple solutions to this, first and foremost simply inlining test instead of creating a separate function, or somehow returning index_parts with the Future, but those solutions leak implementation details and we all know that this is bad.
So, how do I fix this error without breaking encapsulation?

Answer 1

A colleague of mine suggested the following solution:
async fn test<'a>(client: &'a Elasticsearch) -> std::result::Result<Bytes, elasticsearch::Error> {
let index_parts = vec!["foo", "bar"]; // Imagine this list being computed and not literal
let search_response = client
.search(SearchParts::Index(&index_parts))
.from(0)
.size(1000)
.body(json!(
{ "query": { "match_all": { } } }
))
.send()
.await?;
search_response.bytes().await
}
Although I understand that with async, everything inside of the function body is effectively a closure, I feel like there should be a way of doing this without using async as well, but I am not sure.
There is a further problem with this solution though - the returned Future has a lifetime bound to the lifetime of the Elasticsearch reference which leads to issues down the line.
To fix this:
async fn test(client: & Elasticsearch) -> std::result::Result<Bytes, elasticsearch::Error> {
let client = client.clone();
async move {
let index_parts = ["foo", "bar"];
let search_response = client
.search(SearchParts::Index(&index_parts))
.from(0)
.size(1000)
.body(json!(
{ "query": { "match_all": { } } }
))
.send()
.await?;
Ok(search_response.bytes().await?)
}.await
}