Allow binding list of options in `query!` macro

[frxstrem]

I'm using sqlx 0.6.0 against a Postgres database.

If I try to bind to a Vec<Option<_>>, then the query! macro fails to compile:

let inputs: Vec<Option<i32>> = vec![Some(1), Some(2), None];

sqlx::query!(
        r#"
            SELECT * FROM UNNEST($1::int[])
        "#,
// error[E0308]: mismatched types
        &inputs,
//      ^
//      |
//      expected slice `[i32]`, found struct `Vec`
//      expected due to the type of this binding
//
// = note: expected reference `&[i32]`
//            found reference `&Vec<Option<i32>>`
);

If I instead use a Vec<_>, the code compiles without any issue.

If I instead use the sqlx::query function, the code compiles and runs without issue, however this obviously comes with the downside of no compile-time query validation:

let inputs: Vec<Option<i32>> = vec![Some(1), Some(2), None];

let results = sqlx::query(
        r#"
            SELECT * FROM UNNEST($1::int[])
        "#,
    )
    .bind(&inputs)
    .fetch_all(&pool)
    .await?
    .into_iter()
    .map(|row| row.try_get::<Option<i32>, _>(0))
    .collect::<Result<Vec<_>, _>>()?;

println!("{results:?"); // [Some(1), Some(2), None]

Would it be possible to fix this so that the query! macro can also accept vectors of options?

[abonander]

This is supported, sort of. The problem is that the codegen for typechecking bind parameters is very flaky and needs to be rewritten.

You can override typechecking for individual parameters using type hints or casts:

sqlx::query!(
        r#"
            SELECT * FROM UNNEST($1::int[])
        "#,
        &inputs: &[Option<i32>],
);

Wildcards are also supported (this causes typechecking for the parameter to be omitted entirely):

sqlx::query!(
        r#"
            SELECT * FROM UNNEST($1::int[])
        "#,
        // Bindings are always by-reference so an explicit ref isn't usually needed
        inputs: _,
);

[frxstrem]

Thanks, that seems to work!