simplify recursive reference schemas

[samuelcolvin]

fix #60

Turns out I needed this for #127.

ref on any schema type can now be used to make that validator available to be used elsewhere, this involves moving that validator into slots so will be slightly slower than not using ref.

[codecov]

Codecov Report

Merging #130 (1870d3c) into main (0e32399) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #130      +/-   ##
==========================================
+ Coverage   97.30%   97.31%   +0.01%     
==========================================
  Files          40       40              
  Lines        3900     3916      +16     
  Branches       29       28       -1     
==========================================
+ Hits         3795     3811      +16     
  Misses        105      105              

Impacted Files	Coverage Δ
pydantic_core/_types.py	100.00% <100.00%> (ø)
src/validators/mod.rs	98.98% <100.00%> (+0.05%)	⬆️
src/validators/recursive.rs	97.50% <100.00%> (-0.38%)	⬇️

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[adriangb]

Would it be possible to not put it into slots or remove it (haven't dug into the Rust part lately) if it is not used as a recursive ref? That way the schema creators can basically always set ref and not worry about it.

[samuelcolvin]

I guess it might be possible - would involve iterating through the rest of the schema to check.

This would have to be a pre-processing function (in whatever language). I think best to keep it in python when generating the schema, but that opinion might change :-).

[adriangb]

sounds reasonable, at lest it's just performance so it can be optimized later in whatever language

[samuelcolvin]

Would it be possible to not put it into slots or remove it (haven't dug into the Rust part lately) if it is not used as a recursive ref? That way the schema creators can basically always set ref and not worry about it.

This is done in #243 so we can always set ref guilt-free.