[ARROW-10996] [Rust] Return error messages via Result for get_arrow_schema_from_metadata

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.0.0
• Component/s: Rust
• Labels: beginner-friendly pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/26917
• Assignee: Qingyou Meng
• Reporter: Andrew Lamb
• Created: 21/Dec/20 12:56
• Updated: 11/Jan/23 08:16
• Resolved: 01/Jan/21 14:13

Description

While converting from the parquet schema to arrow schema some errors, including those during flatbuffer decoding, can be lost.

This is due to get_arrow_schema_from_metadata returning `Option` rather than `Result`

https://github.com/apache/arrow/pull/8936/files# improved the situation by printing the error to stdout, so the error isn't entirely lost, but this message should be propagated up the call chain as a proper Rust error via a Result.

            match arrow::ipc::root_as_message(slice) {
                Ok(message) => message
                    .header_as_schema()
                    .map(arrow::ipc::convert::fb_to_schema),
                Err(err) => {
                    // The flatbuffers implementation returns an error on verification error.
                    // TODO: return error to caller?
                    eprintln!(
                        "Unable to get root as message stored in {}: {:?}",
                        super::ARROW_SCHEMA_META_KEY,
                        err
                    );
                    None
                }
            }

Issue Links

• links to: GitHub Pull Request #9058