fix: support StringConstraints metadata in SQLAlchemy type generation

Author: Sujit-1509

sqlmodel/_compat.py

@@ -20,6 +20,7 @@
 from pydantic import VERSION as P_VERSION
 from pydantic import BaseModel
 from pydantic import ConfigDict as ConfigDict
+from pydantic import StringConstraints as StringConstraints
 from pydantic._internal._fields import PydanticMetadata
 from pydantic._internal._model_construction import ModelMetaclass as ModelMetaclass
 from pydantic._internal._repr import Representation as Representation
@@ -200,7 +201,7 @@ def get_sa_type_from_field(field: Any) -> Any:
 
 def get_field_metadata(field: Any) -> Any:
     for meta in field.metadata:
-        if isinstance(meta, (PydanticMetadata, MaxLen)):
+        if isinstance(meta, (PydanticMetadata, MaxLen, StringConstraints)):
             return meta
     return FakeMetadata()
 

tests/test_main.py

@@ -216,3 +216,14 @@ class Hero(SQLModel, table=True):
     assert len(foreign_keys) == 1
     assert foreign_keys[0].ondelete == "CASCADE"
     assert team_id_column.nullable is False
+
+
+def test_string_constraints_max_length(clear_sqlmodel):
+    from typing import Annotated
+    from pydantic import StringConstraints
+
+    class Item(SQLModel, table=True):
+        id: int | None = Field(default=None, primary_key=True)
+        name: Annotated[str, StringConstraints(max_length=50)]
+
+    assert Item.__table__.c.name.type.length == 50