Expose regex_engine flag

[utkini]

Change Summary

Pydantic-core 2.10.0 added a new flag regex_engine (pydantic/pydantic-core#983).
This flag is provided in Pydantic and documentation has also been added to it.

Related issue number

fix #7714

Checklist

• The pull request title is a good summary of the changes - it will be used in the changelog
• Unit tests for the changes exist
• Tests pass on CI
• Documentation reflects the changes where applicable
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

Selected Reviewer: @adriangb

[utkini]

Hi @davidhewitt
I think I need your knowledge :)
I added a Python example in the documentation for this feature, but the tests don't work.

I tried to dive deeper but still couldn't figure out exactly how to provide it.
I found in pydantic_core.CoreConfig regex_engine in the description, but I didn't found this attribute in the following in the declaration of class fields.
I tied to add line like regex_engine: Literal['rust-regex', 'python-re'] # default: 'rust-regex' but it didn't solve my problem...

I also tried to pass this parameter here
regex_engine=self.config_dict.get('regex_engine'),
but i got another error:

E   pydantic_core._pydantic_core.SchemaError: Invalid Schema:
E   model.config.regex_engine
E     Extra inputs are not permitted [type=extra_forbidden, input_value='python-re', input_type=str]

Could you help me to understand the whole context? :)
Maybe I missing something about how to provide this parameter to CoreConfig

I also tried to do it through the method in core_schema.str_schema,
but I didn't find any relation between str_schema and ConfigDict class in the documentation.

[davidhewitt]

@utkini thanks for flagging, it's an omission in my part in core - I've pushed pydantic/pydantic-core#1011

Once fixed it should be possible to pass regex_engine in the way you attempted, without getting a SchemaError :)

I'll ping here once pydantic main has this fix merged.

[utkini]

@davidhewitt I'm ready :)
please review

[davidhewitt]

Looks good to me, thanks for pushing this over the line!

[nocturn9x]

I'm still having a hard time understanding exactly where and how CoreConfig should be used to achieve what I need (and the documentation is of no help at all). Any pointers as to where I should look?

[utkini]

Hi @nocturn9x, Could you describe exactly how you want to use this feature?

[nocturn9x]

Hi there, thanks for replying :)

I think I figured it out (I assume it's the __config__ argument of create_model, which is what I am using, unless that expects a ConfigDict?), but the reason why it wasn't "working" as expected was that I hadn't realized Pydantic 2.5 hadn't been released yet, so the regex_engine flag hadn't been exposed, but if things still don't work after it does release, then I'll definitely come back here to ask for more help :))

[utkini]

@nocturn9x, Glad to hear it :)