Improve performance of json lookups in case of errors

[vdebergue]

Pull Request Checklist

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• Have you updated the documentation?
• Have you added tests for any changed functionality?

Purpose

Improve performance of json lookup \ when encountering bad json.

Background Context

When a bad json was encountered, the json object was copied in the error message. This message could often be discarded, when using asOpt for instance.
The issue was especially present when parsing big json objects (> 10MB). As the program was busy serializing the json into a string.
Here we still give the user the available keys in the object to be helpful.

# BEFORE

[info] Benchmark                 (size)   Mode  Cnt      Score      Error   Units
[info] JsLookupBench.badLookup        1  thrpt   10    981.947 ±  443.761  ops/ms
[info] JsLookupBench.badLookup       20  thrpt   10    360.393 ±   39.503  ops/ms
[info] JsLookupBench.badLookup      100  thrpt   10     94.659 ±    9.231  ops/ms
[info] JsLookupBench.goodLookup       1  thrpt   10  32872.983 ± 2745.549  ops/ms
[info] JsLookupBench.goodLookup      20  thrpt   10  25447.611 ± 7564.005  ops/ms
[info] JsLookupBench.goodLookup     100  thrpt   10  30841.130 ±  984.572  ops/ms

# AFTER

[info] JsLookupBench.badLookup        1  thrpt   10   6949.590 ± 770.618  ops/ms
[info] JsLookupBench.badLookup       20  thrpt   10   1644.751 ±  12.360  ops/ms
[info] JsLookupBench.badLookup      100  thrpt   10    393.848 ±   5.391  ops/ms
[info] JsLookupBench.goodLookup       1  thrpt   10  35988.524 ± 645.783  ops/ms
[info] JsLookupBench.goodLookup      20  thrpt   10  33995.451 ± 504.901  ops/ms
[info] JsLookupBench.goodLookup     100  thrpt   10  31899.440 ± 477.421  ops/ms

References

Are there any relevant issues / PRs / mailing lists discussions?

[mkurz]

LGTM