Lots of form code done!

crudkit/core/service.py

@@ -1,7 +1,7 @@
 from typing import Any, Callable, Dict, Iterable, List, Tuple, Type, TypeVar, Generic, Optional, Protocol, runtime_checkable, cast
 from sqlalchemy import and_, func, inspect, or_, text
 from sqlalchemy.engine import Engine, Connection
-from sqlalchemy.orm import Load, Session, raiseload, selectinload, with_polymorphic, Mapper, RelationshipProperty
+from sqlalchemy.orm import Load, Session, raiseload, selectinload, with_polymorphic, Mapper, RelationshipProperty, class_mapper
 from sqlalchemy.orm.attributes import InstrumentedAttribute
 from sqlalchemy.orm.util import AliasedClass
 from sqlalchemy.sql import operators
@@ -12,6 +12,35 @@ from crudkit.core.spec import CRUDSpec
 from crudkit.core.types import OrderSpec, SeekWindow
 from crudkit.backend import BackendInfo, make_backend_info
 
+def _loader_options_for_fields(root_alias, model_cls, fields: list[str]) -> list[Load]:
+    """
+    For bare MANYTOONE names in fields (e.g. "location"), selectinload the relationship
+    and only fetch the related PK. This is enough for preselecting <select> inputs
+    without projecting the FK column on the root model.
+    """
+    opts: list[Load] = []
+    if not fields:
+        return opts
+
+    mapper = class_mapper(model_cls)
+    for name in fields:
+        prop = mapper.relationships.get(name)
+        if not isinstance(prop, RelationshipProperty):
+            continue
+        if prop.direction.name != "MANYTOONE":
+            continue
+
+        rel_attr = getattr(root_alias, name)
+        target_cls = prop.mapper.class_
+        # load_only PK if present; else just selectinload
+        id_attr = getattr(target_cls, "id", None)
+        if id_attr is not None:
+            opts.append(selectinload(rel_attr).load_only(id_attr))
+        else:
+            opts.append(selectinload(rel_attr))
+
+    return opts
+
 @runtime_checkable
 class _HasID(Protocol):
     id: int
@@ -358,6 +387,11 @@ class CRUDService(Generic[T]):
         if params:
             root_fields, rel_field_names, root_field_names = spec.parse_fields()
 
+        fields = (params or {}).get("fields") if isinstance(params, dict) else None
+        if fields:
+            for opt in _loader_options_for_fields(root_alias, self.model, fields):
+                query = query.options(opt)
+
         only_cols = [c for c in root_fields if isinstance(c, InstrumentedAttribute)]
         if only_cols:
             query = query.options(Load(root_alias).load_only(*only_cols))
@@ -365,6 +399,11 @@ class CRUDService(Generic[T]):
         for eager in spec.get_eager_loads(root_alias, fields_map=rel_field_names):
             query = query.options(eager)
 
+        if params:
+            fields = params.get("fields") or []
+            for opt in _loader_options_for_fields(root_alias, self.model, fields):
+                query = query.options(opt)
+
         obj = query.first()
 
         proj = []
@@ -422,6 +461,11 @@ class CRUDService(Generic[T]):
             for eager in spec.get_eager_loads(root_alias, fields_map=rel_field_names):
                 query = query.options(eager)
 
+            if params:
+                fields = params.get("fields") or []
+                for opt in _loader_options_for_fields(root_alias, self.model, fields):
+                    query = query.options(opt)
+
             if filters:
                 query = query.filter(*filters)