fix: merge field constraints across all metadata items

get_field_metadata returned the first field.metadata item matching
(PydanticMetadata, MaxLen) and stopped. Pydantic v2 spreads constraints
across several metadata items, so when a matching item without the
length or precision (for example a pattern or allow_inf_nan constraint)
precedes the item that carries max_length, max_digits, or decimal_places,
those values were silently dropped and the generated SQLAlchemy column
was unbounded (VARCHAR / NUMERIC with no length or precision).

Scan all matching metadata items and merge max_length, max_digits, and
decimal_places into a single result, keeping the first non-None value for
each attribute. Single-metadata fields are unaffected. Add a regression
test covering the order-dependent str and Decimal cases.

Signed-off-by: Anas Khan <83116240+anxkhn@users.noreply.github.com>

Author: anxkhn

sqlmodel/_compat.py

@@ -199,10 +199,15 @@ def get_sa_type_from_field(field: Any) -> Any:
 
 
 def get_field_metadata(field: Any) -> Any:
+    result = FakeMetadata()
     for meta in field.metadata:
         if isinstance(meta, (PydanticMetadata, MaxLen)):
-            return meta
-    return FakeMetadata()
+            for attr in ("max_length", "max_digits", "decimal_places"):
+                if getattr(result, attr, None) is None:
+                    value = getattr(meta, attr, None)
+                    if value is not None:
+                        setattr(result, attr, value)
+    return result
 
 
 def sqlmodel_table_construct(

tests/test_main.py

@@ -216,3 +216,26 @@ 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_metadata_constraints_not_shadowed_by_earlier_metadata(clear_sqlmodel):
+    from decimal import Decimal
+
+    from pydantic import Field as PydanticField
+
+    class Item(SQLModel, table=True):
+        id: int | None = Field(default=None, primary_key=True)
+        code: Annotated[
+            str, PydanticField(pattern=r"^[a-z]+$"), PydanticField(max_length=10)
+        ]
+        price: Annotated[
+            Decimal,
+            PydanticField(allow_inf_nan=False),
+            PydanticField(max_digits=8, decimal_places=2),
+        ]
+
+    code_column = Item.__table__.c.code  # type: ignore[attr-defined]
+    price_column = Item.__table__.c.price  # type: ignore[attr-defined]
+    assert code_column.type.length == 10
+    assert price_column.type.precision == 8
+    assert price_column.type.scale == 2