None behaviour

[samuelcolvin]

Checklist

• Unit tests for the changes exist
• Tests pass on CI and coverage remains at 100%
• Documentation reflects the changes where applicable
• changes/<pull request or issue id>-<github username>.rst file added describing change
  (see changes/README.md for details)

[codecov]

Codecov Report

Merging #803 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #803   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          17     17           
  Lines        2985   2989    +4     
  Branches      580    583    +3     
=====================================
+ Hits         2985   2989    +4

Impacted Files	Coverage Δ
pydantic/color.py	100% <ø> (ø)	⬆️
pydantic/main.py	100% <100%> (ø)	⬆️
pydantic/types.py	100% <100%> (ø)	⬆️
pydantic/schema.py	100% <100%> (ø)	⬆️
pydantic/fields.py	100% <100%> (ø)	⬆️
pydantic/class_validators.py	100% <100%> (ø)	⬆️
pydantic/networks.py	100% <100%> (ø)	⬆️
pydantic/validators.py	100% <100%> (ø)	⬆️
pydantic/error_wrappers.py	100% <100%> (ø)	⬆️

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[samuelcolvin]

This is ready for review.

@dmontagu @tiangolo and anyone else interested: would be great if you could review.

Significant changes:

• validators keyword argument whole has been replaced by each_item, inverse meaning and default to False, eg. now by default validators apply to the whole field not each item. whole is currently still supported with a depreciation warning.
• when using Optional[str] or similar, the None case is now handled explicitly and subfields are not populated, this:
  • improves performance
  • simplifies errors, by remove "value is not None" from appearing in many situations
  • simplifies schema generation that had to explicitly remove the None option from unions
• The custom behaviour for the Json type has been replaced by adding a pre_validator

There are a few other tweaks, but nothing that should effect end users.

[tiangolo]

LGTM 🚀 🎉