Allow hybrid_property, hybrid_method and association_proxy on SQLModel classes

[alvinttang]

Summary

Defining a SQLModel class with a SQLAlchemy descriptor (hybrid_property, hybrid_method, or association_proxy) crashes at class-construction time with:

pydantic.errors.PydanticUserError: A non-annotated attribute was detected: `area = <sqlalchemy.ext.hybrid.hybrid_property object at 0x...>`. ... code='model-field-missing-annotation'

This is the long-standing #299 (20 reactions / 13 comments). The issue was mass-closed on 2026-05-18 alongside many other un-triaged bugs, but the bug is still present on main and community workarounds (subclass SQLModel and set model_config['ignored_types'] yourself) remain the only path. Reopening for review.

Root cause

Pydantic v2's inspect_namespace rejects every non-dunder, non-annotated attribute. hybrid_property / hybrid_method / association_proxy are SQLAlchemy descriptors users add without Python type annotations — that's the whole point of these descriptors. SQLModel never told Pydantic to treat them as ignored types via model_config['ignored_types'], so class construction crashes before SQLModel's metaclass even sees the column logic.

Fix

sqlmodel/main.py (+11 / -1):

• Import AssociationProxy from sqlalchemy.ext.associationproxy and hybrid_method/hybrid_property from sqlalchemy.ext.hybrid.
• Set SQLModel.model_config = SQLModelConfig(from_attributes=True, ignored_types=(hybrid_property, hybrid_method, AssociationProxy)).

Production diff is 10 net LOC.

This is intentionally disjoint and minimal: it stops the crash so users can define these descriptors on SQLModel classes. It does NOT implement DDL/expression generation for hybrid properties (a separate concern that PR #801 attempts in a much larger ~4400-line patch). Most users hitting #299 just want the descriptor to work at the Python level, which this PR enables.

Tests

tests/test_hybrid_property.py (new, 110 LOC, 4 tests):

• test_table_model_allows_hybrid_property — table model + @hybrid_property ; instance returns the computed value.
• test_table_model_allows_hybrid_method — table model + @hybrid_method.
• test_table_model_allows_association_proxy — table model + association_proxy(...).
• test_non_table_model_allows_hybrid_property — non-table model.

RED proof on main (4/4 fail):

pydantic.errors.PydanticUserError: A non-annotated attribute was detected: `area = <sqlalchemy.ext.hybrid.hybrid_property object ...>`

GREEN after patch: 4/4 pass; broader sweep pytest tests/ → 88 passed. ruff check / ruff format --check clean.

Risk notes

• Behaviour change for non-table models that intentionally used hybrid_property as an unannotated raw attribute hoping Pydantic would treat it as a field: vanishingly unlikely, since hybrid_property is meaningless outside an ORM context.
• No SQL-expression support added — leaves that scope to user code or to PR Support hybrid_property, column_property, declared_attr #801.
• Test does not stress the SQL-expression code path of hybrids, only the Python-side descriptor / instance-attribute path that the issue actually reports.

Refs #299

[alvinttang]

Friendly bump: this PR has a required check-labels CI gate that needs a maintainer to apply the bug label (#299 is the underlying bug; tests are RED-on-main / GREEN-with-patch). Happy to address any review feedback in the meantime.