Adding full support for Pydantic 2, dropping support for Pydantic 1 in 0.3.0

[eyurtsev]

We’re considering dropping support for Pydantic 1 in the 0.3.x release, and migrating to Pydantic 2 proper. Pydantic 2 now accounts for 50% of pydantic downloads, so it’ll soon account for the majority of Pydantic usage. The timeline for the migration is TBD, but will likely be around July-Sep. Please vote 👍 / 👎 if you think this is reasonable.

We’ve been providing pseudo support for Pydantic 2 since August of 2023 via the Pydantic v1 namespace. This change allowed users to install either Pydantic 1 or Pydantic 2 in their environment and interact with LangChain APIs via pydantic models constructed using v1 functionality.

This migration would be a breaking change as users will have to upgrade their code bases to use Pydantic 2. Users could adapt a similar strategy to that used by LangChain and upgrade first to the v1 namespace of Pydantic 2.

Please let us know whether this sounds like a reasonable timeline for folks.

[eyurtsev]

For folks 👎 , could you please provide a bit of context about why the timeline does not work?

Does the the gradual transition into v1 namespace in pydantic not work for you? Why not?

[169]

I strongly support the decision to drop support for Pydantic 1 in version 0.3. If we follow the official Migration Guide, it doesn’t seem like it will take much time and effort.

[eyurtsev]

We're looking for any feedback that folks have here: #24405