Re: [PATCH proxmox] oci: drop unnecessary Result from layer decode_fn

[Wolfgang Bumiller <w.bumiller@proxmox.com>]

On Tue, Oct 13, 2026 at 10:30:37AM +0200, Filip Schauer wrote:
> zstd::Decoder::new cannot fail (see gyscos/zstd-rs#281), so simplify

I don't want to rely on something happening in a dependency's wrapped
library like that.
Let's just wait for `zstd` to drop the `Result` *or* at the very least
make the error case `Infallible`/`!`.

> DecodeFn to return Box<dyn Read> directly.
> 
> Signed-off-by: Filip Schauer <f.schauer@proxmox.com>
> ---
>  proxmox-oci/src/lib.rs | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/proxmox-oci/src/lib.rs b/proxmox-oci/src/lib.rs
> index b274e46a..3b6dbeb0 100644
> --- a/proxmox-oci/src/lib.rs
> +++ b/proxmox-oci/src/lib.rs
> @@ -201,16 +201,17 @@ fn extract_image_rootfs<R: Read + Seek, P: AsRef<Path>>(
>              .open_blob(layer_descriptor.digest())
>              .ok_or(ExtractError::MissingLayerFile(layer_digest))?;
>  
> -        type DecodeFn<T> = Box<dyn for<'a> Fn(&'a mut T) -> io::Result<Box<dyn Read + 'a>>>;
> +        type DecodeFn<T> = Box<dyn for<'a> Fn(&'a mut T) -> Box<dyn Read + 'a>>;
>          let decode_fn: DecodeFn<OciTarImageBlob<R>> = match layer_descriptor.media_type() {
>              MediaType::ImageLayer | MediaType::ImageLayerNonDistributable => {
> -                Box::new(|file| Ok(Box::new(file)))
> +                Box::new(|file| Box::new(file))
>              }
>              MediaType::ImageLayerGzip | MediaType::ImageLayerNonDistributableGzip => {
> -                Box::new(|file| Ok(Box::new(GzDecoder::new(file))))
> +                Box::new(|file| Box::new(GzDecoder::new(file)))
>              }
>              MediaType::ImageLayerZstd | MediaType::ImageLayerNonDistributableZstd => {
> -                Box::new(|file| Ok(Box::new(zstd::Decoder::new(file)?)))
> +                // https://github.com/gyscos/zstd-rs/issues/281
> +                Box::new(|file| Box::new(zstd::Decoder::new(file).expect("infallible")))
>              }
>              // Error on any other non-ImageLayer related media types.
>              // Match explicitly to avoid missing new image layer types when oci-spec updates.
> @@ -226,9 +227,9 @@ fn extract_image_rootfs<R: Read + Seek, P: AsRef<Path>>(
>              }
>          };
>  
> -        apply_whiteouts(&mut decode_fn(&mut layer_file)?, &target_path)?;
> +        apply_whiteouts(&mut decode_fn(&mut layer_file), &target_path)?;
>          layer_file.seek(SeekFrom::Start(0))?;
> -        extract_archive(&mut decode_fn(&mut layer_file)?, &target_path)?;
> +        extract_archive(&mut decode_fn(&mut layer_file), &target_path)?;
>  
>          oci_tar_image = layer_file.into_oci_tar_image();
>      }
> -- 
> 2.47.3