refactor: Centralize JSON SerDe into helper functions

[BuzzCutNorman]

I was wondering if it made sense to move all the serialize and deserialize functions into a helper library that we could reference in other areas. I thought singer_sdk.helper._util could be a place for it.

[codspeed-hq]

CodSpeed Performance Report

Merging #2259 will not alter performance

_{Comparing BuzzCutNorman:refactor-move-json-serde-to-helpers (f848370) with main (b065e5e)}

Summary

✅ 6 untouched benchmarks

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.41%. Comparing base (b065e5e) to head (362ad22).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2259      +/-   ##
==========================================
+ Coverage   89.23%   89.41%   +0.18%     
==========================================
  Files          54       58       +4     
  Lines        4782     4779       -3     
  Branches      935      933       -2     
==========================================
+ Hits         4267     4273       +6     
+ Misses        359      353       -6     
+ Partials      156      153       -3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[BuzzCutNorman]

@edgarrmondragon when you get a chance, please take a look and let me know what you think of this idea. I was working on the msgspec pr and found I had to copy the json encoder code over from io_base to _flattening. After doing that I thought it might make sense to move these functions into the helpers.

[edgarrmondragon]

So we currently have this

$ rg -. serde singer_sdk
singer_sdk/helpers/_flattening.py
13:from singer_sdk._singerlib.serde import serialize_json

singer_sdk/contrib/batch_encoder_jsonl.py
9:from singer_sdk._singerlib.serde import serialize_json

singer_sdk/_singerlib/messages.py
11:from singer_sdk._singerlib.serde import serialize_json

singer_sdk/tap_base.py
13:from singer_sdk._singerlib.serde import serialize_json

singer_sdk/io_base.py
14:from singer_sdk._singerlib.serde import deserialize_json

singer_sdk/connectors/sql.py
15:from singer_sdk._singerlib import CatalogEntry, MetadataMapping, Schema, serde
1167:        return serde.serialize_json(obj)
1183:        return serde.deserialize_json(json_str)

singer_sdk/sinks/core.py
19:from singer_sdk._singerlib.serde import deserialize_json

And I think not all of these need to factor out SerDe. In particular, tap_base.py only uses json.dumps to print the discovered catalog. That operation doesn't need to be extremely performant nor does it need (so far as a I know) special decimal or NaN handling.

The others, I'm not sure currently:

• Flattening may benefit since it's done to all records in a stream.
• JSONL Batch reading/writing could also benefit, maybe greatly
• Anything to do with Singer message writing and reading does certainly benefit
• SQL JSON column reading/writing is an interesting case. I think it might benefit.

These four cases still architecturally benefit from having a centralized approach that was missing previously, and it was causing inconsistent handling of whitespace and decimals.

[edgarrmondragon]

These are the only breaking API changes in this PR according to griffe:

singer_sdk/mapper_base.py:0: InlineMapper.format_message: Public object was removed
singer_sdk/mapper_base.py:0: InlineMapper.write_message: Public object was removed
singer_sdk/mapper_base.py:0: InlineMapper.listen: Public object was removed
singer_sdk/mapper_base.py:0: InlineMapper.deserialize_json: Public object was removed
singer_sdk/tap_base.py:0: SQLTap.format_message: Public object was removed
singer_sdk/tap_base.py:0: SQLTap.write_message: Public object was removed
singer_sdk/tap_base.py:0: Tap.format_message: Public object was removed
singer_sdk/tap_base.py:0: Tap.write_message: Public object was removed
singer_sdk/target_base.py:0: SQLTarget.listen: Public object was removed
singer_sdk/target_base.py:0: SQLTarget.deserialize_json: Public object was removed
singer_sdk/target_base.py:0: Target.listen: Public object was removed
singer_sdk/target_base.py:0: Target.deserialize_json: Public object was removed
singer_sdk/io_base.py:0: logger: Public object was removed
singer_sdk/io_base.py:0: SingerReader: Public object was removed
singer_sdk/io_base.py:0: SingerWriter: Public object was removed

I think these are acceptable. The plugin class methods weren't really removed, but the superclass now lives in the private _singerlib submodule. The important singer_sdk.io_base members are not really removed thanks to the __all__ declaration in singer_sdk._singerlib._encoding.

[edgarrmondragon]

Thanks @BuzzCutNorman!