Additional fixes and expansions on field dependencies. Still a WIP.

crudkit/core/base.py

@@ -1,8 +1,21 @@
-from sqlalchemy import Column, Integer, DateTime, Boolean, String, JSON, func
-from sqlalchemy.orm import declarative_mixin, declarative_base
+from sqlalchemy import Column, Integer, DateTime, Boolean, String, JSON, func, inspect
+from sqlalchemy.orm import declarative_mixin, declarative_base, NO_VALUE
 
 Base = declarative_base()
 
+def _safe_get_loaded_attr(obj, name):
+    try:
+        st = inspect(obj)
+        attr = st.attrs.get(name)
+        if attr is not None:
+            val = attr.loaded_value
+            return None if val is NO_VALUE else val
+        if name in st.dict:
+            return st.dict.get(name)
+        return None
+    except Exception:
+        return None
+
 @declarative_mixin
 class CRUDMixin:
     id = Column(Integer, primary_key=True)

crudkit/core/service.py

@@ -3,6 +3,7 @@ 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, class_mapper, ColumnProperty
 from sqlalchemy.orm.attributes import InstrumentedAttribute
+from sqlalchemy.orm.base import NO_VALUE
 from sqlalchemy.orm.util import AliasedClass
 from sqlalchemy.sql import operators
 from sqlalchemy.sql.elements import UnaryExpression
@@ -12,6 +13,39 @@ from crudkit.core.spec import CRUDSpec
 from crudkit.core.types import OrderSpec, SeekWindow
 from crudkit.backend import BackendInfo, make_backend_info
 
+def _expand_requires(model_cls, fields):
+    out, seen = [], set()
+    def add(f):
+        if f not in seen:
+            seen.add(f); out.append(f)
+
+    for f in fields:
+        add(f)
+        parts = f.split(".")
+        cur_cls = model_cls
+        prefix = []
+
+        for p in parts[:-1]:
+            rel = getattr(cur_cls.__mapper__.relationships, 'get', lambda _: None)(p)
+            if not rel:
+                cur_cls = None
+                break
+            cur_cls = rel.mapper.class_
+            prefix.append(p)
+
+        if cur_cls is None:
+            continue
+
+        leaf = parts[-1]
+        deps = (getattr(cur_cls, "__crudkit_field_requires__", {}) or {}).get(leaf)
+        if not deps:
+            continue
+
+        pre = ".".join(prefix)
+        for dep in deps:
+            add(f"{pre + '.' if pre else ''}{dep}")
+    return out
+
 def _is_rel(model_cls, name: str) -> bool:
     try:
         prop = model_cls.__mapper__.relationships.get(name)
@@ -232,7 +266,10 @@ class CRUDService(Generic[T]):
           - forward/backward seek via `key` and `backward`
         Returns a SeekWindow with items, first/last keys, order spec, limit, and optional total.
         """
-        session = self.session
+        fields = list(params.get("fields", []))
+        if fields:
+            fields = _expand_requires(self.model, fields)
+            params = {**params, "fields": fields}
         query, root_alias = self.get_query()
 
         spec = CRUDSpec(self.model, params or {}, root_alias)