[RUST] Fix #22356 / Introduce useSerdePathToError option to improve JSON error messages

[Levilutz]

This PR contains the proposed solution to #22356 - introducing an optional useSerdePathToError config option for the Rust generator (defaulting to false) that adds the serde_path_to_error library for improving Serde error responses. The linked issue contains an example before / after error message.

Change breakdown:

• Add a useSerdePathToError config option to the Rust generator
• Add a conditional serde_path_to_error = "^0.1" dependency
• Add a conditional SerdePathToError error type and all appropriate methods
• Conditionally switch the main API response parse between serde_json::from_str and the appropriate serde_path_to_error equivalent
• Add a new sample: samples/client/petstore/rust/reqwest/petstore-serde-path-to-error

Notably, I'm leaving the 4XX/5XX-path serde_json::from_str untouched. This path will include the both the received raw response body and (if parseable) the JSON response body. This should improve debug-ability sufficiently to not need this additional library.

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[Levilutz]

👋 @frol @farcaller @richardwhiuk @paladinzh @jacob-pro @dsteeley let me know if this looks good to you, any and all feedback would be appreciated 🙇

[wing328]

thanks for the PR

This is a broad issue people have with the serde library, and thankfully there's an established library addressing this gap - serde_path_to_error.

if that's the case, shall we add this feature without the option to start with as it should benefit everyone using the auto-generated Rust SDK?

[Levilutz]

thanks for the PR

This is a broad issue people have with the serde library, and thankfully there's an established library addressing this gap - serde_path_to_error.

if that's the case, shall we add this feature without the option to start with as it should benefit everyone using the auto-generated Rust SDK?

@wing328 Thanks for the quick response!

I was considering that as well. I'm erring on the conservative side for three reasons:

• It's "one more dependency" that's not strictly necessary
• It introduces another possible error signature - users may have their own custom handling for Serde errors, and not want a new SerdePathToError type that they have to add code to handle. This constitutes a breaking API change imo
• The issue at serde-rs/json#173 has been open for ~9 years, indicating some reluctance to include this functionality in the Serde standard library as-is. While the reasons aren't clarified, I still want to take that as an indicator of something.

[wing328]

looks good to me

let's give it a try

thanks for your contribution