refactor: Migration of json utilities from core

[eyalezer]

SUMMARY

initial step of refactoring JSON utilities

• migration of all json utils from utils.core to utils.json
• refactored all referenced usage of those utils to the new json module
• added and fixed some tests
• removed unused code
• following fix: utf-16 json encoder support #28486 more instances discovered and fixed at:
  • Sqllab results api
  • Charts data api

[eyalezer]

@mistercrunch - tests from last commit #28486 still covers for the encoding part.

[codecov]

Codecov Report

Attention: Patch coverage is 86.76471% with 18 lines in your changes missing coverage. Please review.

Project coverage is 83.50%. Comparing base (76d897e) to head (929fc12).
Report is 1094 commits behind head on master.

Files with missing lines	Patch %	Lines
superset/utils/json.py	86.95%	12 Missing ⚠️
superset/views/chart/views.py	33.33%	2 Missing ⚠️
superset/models/core.py	66.66%	1 Missing ⚠️
superset/views/api.py	50.00%	1 Missing ⚠️
superset/views/tags.py	66.66%	1 Missing ⚠️
superset/viz.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #28522       +/-   ##
===========================================
+ Coverage   60.48%   83.50%   +23.01%     
===========================================
  Files        1931      522     -1409     
  Lines       76236    37485    -38751     
  Branches     8568        0     -8568     
===========================================
- Hits        46114    31301    -14813     
+ Misses      28017     6184    -21833     
+ Partials     2105        0     -2105     

Flag	Coverage Δ
hive	49.11% <50.00%> (-0.06%)	⬇️
javascript	?
mysql	77.18% <83.82%> (?)
postgres	77.29% <84.55%> (?)
presto	53.66% <50.73%> (-0.15%)	⬇️
python	83.50% <86.76%> (+20.01%)	⬆️
sqlite	76.74% <84.55%> (?)
unit	58.96% <65.44%> (+1.34%)	⬆️

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[mistercrunch]

Starting to feel like we need a refactor of some kind here as this isn't DRY, maybe moving some things to a new superset/utils/json.py, taking all the json-related stuff in superset/utils/core.py, and moving all this recent utf-16 handling in there too.

I think I started this refactor before in a branch but never carried though. Let me push the branch for reference. Are you interested in taking this on?

[mistercrunch]

Here's the branch https://github.com/apache/superset/compare/refactor_json?expand=1, looks like I lost the json.py file along the way.... For now the goal would be to move the json-related function from utils/core to utils/json, and refactor the recent utf-16 handling in there. Eventually I'd like to also make sure all usage of json.(load|dump)(s)() would go through this module and use the proper encoders.

[eyalezer]

definitely felt the same seeing things being repeated more than once while dealing with this non UTF-8 bytes.
for starters lets try to move all of those recent UTF-16 handling to this module and then see how goes.

[mistercrunch]

If you git grep json.dumps you'll see there's quite a bit to centralize, we don't have to do it all at once though.

[eyalezer]

@mistercrunch - i've tried to keep it as small as possible for this first phase but it ended up with 30 files changed after all 😏

next phase (as mentioned) needs to be the refactoring of any json.(load/s|dump/s) to use this module which looks like it's gonna be a huge refactoring ~250+ files at least. so probably it's better to split it up anyway.

[mistercrunch]

Did a quick pass and overall LGTM, looking to do another thorough pass on it, but seems safe overall

[mistercrunch]

Did another, more thorough pass and everything LGTM. Thanks for the refactor!

[eyalezer]

@mistercrunch - with pleasure.
since i got my head into this I have begun working on the subsequent stage of the refactoring. It is likely that I will submit another pull request regarding this matter in the near future.