PostgreSQL querys don't support nullable output arrays correctly

[C0D3-M4513R]

I have found these related issues/pull requests

#3775

Description

When having a query that returns an array with nullable values, it is assumed, that the entire array contents are non-nullable.

Reproduction steps

Code:

    let v = sqlx::query!(r#"Select ARRAY[null, false, true] as "test!""#)
        .fetch_one(get_mysql().await).await.expect("test");
    let test:Vec<Option<bool>> = v.test;

Error message:

error[E0308]: mismatched types
  --> app/src/main.rs:56:34
   |
56 |     let test:Vec<Option<bool>> = v.test;
   |              -----------------   ^^^^^^ expected `Vec<Option<bool>>`, found `Vec<bool>`
   |              |
   |              expected due to this
   |
   = note: expected struct `Vec<std::option::Option<bool>>`
              found struct `Vec<bool>`

SQLx version

0.8.3

Enabled SQLx features

["postgres", "runtime-tokio-rustls"]

Database server and version

postgres (PostgreSQL) 16.6

Operating system

Linux nixos-pc 6.12.16 #1-NixOS SMP PREEMPT_DYNAMIC Fri Feb 21 13:01:47 UTC 2025 x86_64 GNU/Linux

Rust version

rustc 1.85.0 (4d91de4e4 2025-02-17)

[abonander]

Null-checking the contents of arrays is nearly impossible given the current architecture of the macros. There's no standard constraint we can use to assert that the array cannot contain NULL. The default assumption is that the elements should not be NULL because it would be much more annoying to deal with if it always inferred Vec<Option<T>>. This is one of the situations where you're meant to use a type override: https://docs.rs/sqlx/latest/sqlx/macro.query.html#force-a-differentcustom-type