More verbose error

[vustef]

In exception like:

Unexpected => Failed to load manifest list in cache, source: Unexpected => Failure in doing io operation, source: Unexpected (persistent) at read, context: { url: https://nsh-ibt.s3.us-east-1.amazonaws.com/customer_iceberg.5Et4fZvD/metadata/snap-5057205298355132429-1-92c679c0-2a3c-4fc5-9422-7c1736682697.avro, called: http_util::Client::send, service: s3, path: customer_iceberg.5Et4fZvD/metadata/snap-5057205298355132429-1-92c679c0-2a3c-4fc5-9422-7c1736682697.avro, range: 0- } => send http request, source: error sending request for url (https://nsh-ibt.s3.us-east-1.amazonaws.com/customer_iceberg.5Et4fZvD/metadata/snap-5057205298355132429-1-92c679c0-2a3c-4fc5-9422-7c1736682697.avro)

root cause is being swallowed. The error ends at error sending request for url (...) without saying why (DNS failure? TLS error? timeout? connection refused?).

The iceberg Display implementation recurses through sources:

// error.rs:167
if let Some(source) = &self.source {
write!(f, ", source: {source}")?; // {source} = anyhow Display = inner error's Display
}

This works for iceberg and opendal errors because they both include source: in their Display. But at the bottom of the chain, reqwest::Error::Display only shows "error sending request for url (...)" - it does not include its own .source() (which would be the actual hyper/DNS/TLS error).

The chain stops because reqwest::Error follows the standard Rust convention where Display only shows the current error, not the source.

Now for the original error, the output would look something like:

Unexpected => Failure in doing io operation (hidden sources: hyper::Error(...): dns error: failed to lookup address information: Name or service not  known), source: Unexpected (persistent) at read, context: { ... } => send http request, source: error sending request for url (...)

The (hidden sources: ...) part surfaces the details that reqwest's Display was hiding, while the structured source: chain remains unchanged.

[gbrgr]

LGTM!