stop clone-ing serializers

[davidhewitt]

Change Summary

In general, cloning serializers is a potentially expensive runtime operation; we should instead store Arc<CombinedSerializer> and cheaply clone that where needed.

Related issue number

N/A

Checklist

• Unit tests for the changes exist
• Documentation reflects the changes where applicable
• Pydantic tests pass with this pydantic-core (except for expected changes)
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.53%. Comparing base (ab503cb) to head (99b8e85).
Report is 143 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1402      +/-   ##
==========================================
- Coverage   90.21%   89.53%   -0.69%     
==========================================
  Files         106      109       +3     
  Lines       16339    17345    +1006     
  Branches       36       41       +5     
==========================================
+ Hits        14740    15529     +789     
- Misses       1592     1796     +204     
- Partials        7       20      +13     

Files	Coverage Δ
src/serializers/computed_fields.rs	97.84% <ø> (+0.16%)	⬆️
src/serializers/fields.rs	96.29% <ø> (+0.65%)	⬆️
src/serializers/infer.rs	94.06% <100.00%> (-1.06%)	⬇️
src/serializers/shared.rs	79.03% <ø> (-0.19%)	⬇️
src/serializers/type_serializers/any.rs	100.00% <100.00%> (ø)
src/serializers/type_serializers/bytes.rs	100.00% <ø> (ø)
src/serializers/type_serializers/dataclass.rs	85.44% <ø> (+0.61%)	⬆️
src/serializers/type_serializers/datetime_etc.rs	100.00% <ø> (ø)
src/serializers/type_serializers/decimal.rs	95.23% <ø> (ø)
src/serializers/type_serializers/definitions.rs	85.00% <ø> (-15.00%)	⬇️
... and 22 more

... and 34 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update fd81a75...99b8e85. Read the comment docs.

[codspeed-hq]

CodSpeed Performance Report

Merging #1402 will not alter performance

_{Comparing davidhewitt:dh/no-clone-serializers (99b8e85) with main (fd81a75)}

Summary

✅ 155 untouched benchmarks

[sydney-runkle]

Great! It's cool to learn about new rust concepts through reviewing your PRs.

I'd be happy to open a PR like this tomorrow for validators, if you think that would help as well :).

[davidhewitt]

While the offer is welcome, actually I did a similar change already for validators in 5f14973

Though in the same line, what we should try to work towards is resolving this TODO:

pydantic-core/Cargo.toml

Lines 30 to 32 in 7368c1f

	# TODO it would be very nice to remove the "py-clone" feature as it can panic,
	# but needs a bit of work to make sure it's not used in the codebase
	pyo3 = { version = "0.22.2", features = ["generate-import-lib", "num-bigint", "py-clone"] }

Last I checked the hard bit is that we clone error values; we might be able to restructure errors to remove the need.