Show the errored path on JsonDataError

[dahlia]

Motivation

Previously, it was difficult to find out the path in the deep JSON tree at which a deserialization error occurred.

Solution

This patch makes an error message to contain the errored path. In order to find out the path, I added serde_path_to_error, a new optional dependency.

[davidpdrsn]

Thanks! I think it looks good.

Worth nothing that this changes the inner error of a JsonRejection from serde_json::Error to serde_path_to_error::Error<serde_json::Error>. Thats not considered a breaking change but I think we should mention it in the changelog regardless.

[davidpdrsn]

Wanna change this to match on the whole text, instead of using contains? Then its easier to see what the final result actually is.

[dahlia]

Amended!

[jplatte]

I wonder whether this has significant performance implications for parsing. Maybe it should only be part of axum-extra (for now) if that is the case?

[davidpdrsn]

Good point. I ran the benchmark:

main

  Beginning round 1...
  Benchmarking 10 connections @ http://0.0.0.0:49942 for 10 second(s)
    Latencies:
      Avg      Stdev    Min      Max
      0.07ms   0.02ms   0.02ms   2.63ms
    Requests:
      Total: 1490865 Req/Sec: 149077.94
    Transfer:
      Total: 106.63 MB Transfer Rate: 10.66 MB/Sec

json-error-path branch

  Benchmarking 10 connections @ http://0.0.0.0:49918 for 10 second(s)
    Latencies:
      Avg      Stdev    Min      Max
      0.07ms   0.02ms   0.02ms   0.67ms
    Requests:
      Total: 1517780 Req/Sec: 151771.58
    Transfer:
      Total: 108.56 MB Transfer Rate: 10.86 MB/Sec

This branch is faster, which is odd so might just be noise and no loss of performance.

[jplatte]

That's the receive-json bench? Seems good if there's no (measureable) slowdown.

[davidpdrsn]

That's the receive-json bench?

Yes

[dahlia]

@davidpdrsn I amended the commit. Could you take a look again?

[davidpdrsn]

Thanks! Just a couple of minor things.

[dahlia]

@davidpdrsn Fixed the changelogs!

[davidpdrsn]

Thanks!