allow Config.field to update a Field

[samuelcolvin]

Change Summary

Allow element of Config.field to update elements of a Field

Example of usage:

Related issue number

fix #2426

supersedes #2437

Questions

• could this break any assumed existing behaviour?
• do any docs need to be updated? If so, what?

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>.md file added describing change

[codecov]

Codecov Report

Merging #2461 (9826145) into master (3f84d14) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master     #2461   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           25        25           
  Lines         5100      5109    +9     
  Branches      1048      1050    +2     
=========================================
+ Hits          5100      5109    +9     

Impacted Files	Coverage Δ
pydantic/main.py	100.00% <ø> (ø)
pydantic/fields.py	100.00% <100.00%> (ø)

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[PrettyWood]

LGTM otherwise! Just a question on constraints attributes that don't have None as default value

[PrettyWood]

Suggested change

	if current_value is None:
	if current_value is self.__field_constraints__.get(attr_name, None):

I wonder if we should do this to support

from pydantic import BaseModel, Field


class Foo(BaseModel):
    a: str = Field(...)

    class Config:
        validate_assignment = True
        fields = {'a': {'allow_mutation': False}}

f = Foo(a='x')
f.a = 'y'  # should fail

[PrettyWood]

LOL 😄 just saw your last commit

[samuelcolvin]

ha, I was just writing a comment about allow_mutation.

[samuelcolvin]

For me this is now ready, I'll merge once passing.

@PrettyWood are you okay for me to release v1.8.1 after this? I think we have fixed everything that has been reported.

[PrettyWood]

@samuelcolvin Yes!