rroelke opened a new issue, #15860:
URL: https://github.com/apache/datafusion/issues/15860
Minimal reproducer:
Cargo.toml
```
[package]
name = "datafusion-bug-repro"
edition = "2024"
[dependencies]
datafusion-common = { version = "47", features = ["avro"] }
```
src/lib.rs
```
use datafusion_common::error::DataFusionError;
pub fn foo() -> Result<(), DataFusionError> {
Ok(())
}
```
And then:
```
$ rustc --version
rustc 1.88.0-nightly (d7ea436a0 2025-04-24)
$ cargo clippy
warning: the `Err`-variant returned from this function is very large
--> src/lib.rs:3:17
|
3 | pub fn foo() -> Result<(), DataFusionError> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the `Err`-variant is at
least 256 bytes
|
= help: try reducing the size of `datafusion_common::DataFusionError`, for
example by boxing large elements or replacing it with
`Box<datafusion_common::DataFusionError>`
= help: for further information visit
https://rust-lang.github.io/rust-clippy/master/index.html#result_large_err
= note: `#[warn(clippy::result_large_err)]` on by default
warning: `datafusion-bug-repro` (lib) generated 1 warning
```
From the [lint
documentation](https://rust-lang.github.io/rust-clippy/master/index.html#result_large_err):
> Why is this bad?
A Result is at least as large as the Err-variant. While we expect that
variant to be seldom used, the compiler needs to reserve and move that much
memory every single time. Furthermore, errors are often simply passed up the
call-stack, making use of the ?-operator and its type-conversion mechanics. If
the Err-variant further up the call-stack stores the Err-variant in question
(as library code often does), it itself needs to be at least as large,
propagating the problem.
This is probably reason enough to fix this, but the reason I'm filing it is
actually because of the impact it has on downstream projects. Downstream
projects which can return `Result<T, DataFusionError>` (very likely) will also
see this lint in their own projects, and disabling it is undesirable for the
reasons stated above.
**Exit criteria**
This issue can be closed when this lint is fixed (not ignored).
Specifically `DataFusionError` must have a small size.
**Investigation and recommended fix**
This lint only appears when `features = ["avro"]` is used. This enables the
[`AvroError`
variant](https://rust-lang.github.io/rust-clippy/master/index.html#result_large_err)
of `DataFusionError`. The easiest thing to do would be to box the AvroError
as the lint suggests.
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