Starting to get nested loading working. Still a WIP.

crudkit/core/base.py

@@ -1,6 +1,6 @@
-from typing import Any, Dict, Iterable, List, Tuple
+from typing import Any, Dict, Iterable, List, Tuple, Set
 from sqlalchemy import Column, Integer, DateTime, Boolean, String, JSON, func, inspect
-from sqlalchemy.orm import declarative_mixin, declarative_base, NO_VALUE
+from sqlalchemy.orm import declarative_mixin, declarative_base, NO_VALUE, RelationshipProperty
 
 Base = declarative_base()
 
@@ -17,6 +17,69 @@ def _safe_get_loaded_attr(obj, name):
     except Exception:
         return None
 
+def _identity_key(obj) -> Tuple[type, Any]:
+    try:
+        st = inspect(obj)
+        return (type(obj), st.identity_key[1][0] if st.identity_key else id(obj))
+    except Exception:
+        return (type(obj), id(obj))
+
+def _is_collection_rel(prop: RelationshipProperty) -> bool:
+    try:
+        return prop.uselist is True
+    except Exception:
+        return False
+
+def _serialize_simple_obj(obj) -> Dict[str, Any]:
+    """Columns only (no relationships)."""
+    out: Dict[str, Any] = {}
+    for cls in obj.__class__.__mro__:
+        if hasattr(cls, "__table__"):
+            for col in cls.__table__.columns:
+                name = col.name
+                try:
+                    out[name] = getattr(obj, name)
+                except Exception:
+                    out[name] = None
+    return out
+
+def _serialize_loaded_rel(obj, name, *, depth: int, seen: Set[Tuple[type, Any]], embed: Set[str]) -> Any:
+    """
+    Serialize relationship 'name' already loaded on obj.
+    - If in 'embed' (or depth > 0 for depth-based walk), recurse.
+    - Else, return None (don’t lazy-load).
+    """
+    val = _safe_get_loaded_attr(obj, name)
+    if val is None:
+        return None
+
+    # Decide whether to recurse into this relationship
+    should_recurse = (depth > 0) or (name in embed)
+
+    if isinstance(val, list):
+        if not should_recurse:
+            # Emit a light list of child primary data (id + a couple columns) without recursion.
+            return [_serialize_simple_obj(child) for child in val]
+        out = []
+        for child in val:
+            ik = _identity_key(child)
+            if ik in seen:  # cycle guard
+                out.append({"id": getattr(child, "id", None)})
+                continue
+            seen.add(ik)
+            out.append(child.as_tree(embed_depth=max(depth - 1, 0), embed=embed, _seen=seen))
+        return out
+
+    # Scalar relationship
+    child = val
+    if not should_recurse:
+        return _serialize_simple_obj(child)
+    ik = _identity_key(child)
+    if ik in seen:
+        return {"id": getattr(child, "id", None)}
+    seen.add(ik)
+    return child.as_tree(embed_depth=max(depth - 1, 0), embed=embed, _seen=seen)
+
 def _split_field_tokens(fields: Iterable[str]) -> Tuple[List[str], Dict[str, List[str]]]:
     """
     Split requested fields into:
@@ -116,6 +179,49 @@ class CRUDMixin:
     created_at = Column(DateTime, default=func.now(), nullable=False)
     updated_at = Column(DateTime, default=func.now(), nullable=False, onupdate=func.now())
 
+    def as_tree(
+            self,
+            *,
+            embed_depth: int = 0,
+            embed: Iterable[str] | None = None,
+            _seen: Set[Tuple[type, Any]] | None = None,
+        ) -> Dict[str, Any]:
+            """
+            Recursive, NON-LAZY serializer.
+              - Always includes mapped columns.
+              - For relationships: only serializes those ALREADY LOADED.
+              - Recurses either up to embed_depth or for specific names in 'embed'.
+              - Keeps *_id columns alongside embedded objects.
+              - Cycle-safe via _seen.
+            """
+            seen = _seen or set()
+            ik = _identity_key(self)
+            if ik in seen:
+                return {"id": getattr(self, "id", None)}
+            seen.add(ik)
+
+            data = _serialize_simple_obj(self)
+
+            # Determine which relationships to consider
+            try:
+                st = inspect(self)
+                mapper = st.mapper
+                embed_set = set(str(x).split(".", 1)[0] for x in (embed or []))  # top-level names
+                for name, prop in mapper.relationships.items():
+                    # Only touch relationships that are already loaded; never lazy-load here.
+                    rel_loaded = st.attrs.get(name)
+                    if rel_loaded is None or rel_loaded.loaded_value is NO_VALUE:
+                        continue
+
+                    data[name] = _serialize_loaded_rel(
+                        self, name, depth=embed_depth, seen=seen, embed=embed_set
+                    )
+            except Exception:
+                # If inspection fails, we just return columns.
+                pass
+
+            return data
+
     def as_dict(self, fields: list[str] | None = None):
         """
         Serialize the instance.
@@ -140,25 +246,34 @@ class CRUDMixin:
 
             out: Dict[str, Any] = {}
 
-            # Always include id unless user explicitly listed fields and included id already
+            # Always include id unless the caller explicitly listed fields containing id
             if "id" not in req_list and hasattr(self, "id"):
                 try:
                     out["id"] = getattr(self, "id")
                 except Exception:
                     pass
 
+            # Handle scalar tokens (may be columns, hybrids/properties, or relationships)
             for name in scalars:
                 # Try loaded value first (never lazy-load)
                 val = _safe_get_loaded_attr(self, name)
 
-                # if still None, allow a final-hop getattr for root scalars
-                # so hybrids / @property can compute (they won't traverse relationships).
+                # Final-hop getattr for root scalars (hybrids/@property) so they can compute.
                 if val is None:
                     try:
                         val = getattr(self, name)
                     except Exception:
                         val = None
 
+                # If it's a scalar ORM object (relationship), serialize its columns
+                try:
+                    st = inspect(val)  # will raise if not an ORM object
+                    if getattr(st, "mapper", None) is not None:
+                        out[name] = _serialize_simple_obj(val)
+                        continue
+                except Exception:
+                    pass
+
                 # If it's a collection and no subfields were requested, emit a light list
                 if isinstance(val, (list, tuple)):
                     out[name] = [_serialize_leaf(v) for v in val]
@@ -169,7 +284,7 @@ class CRUDMixin:
             for root, tails in groups.items():
                 root_val = _safe_get_loaded_attr(self, root)
                 if isinstance(root_val, (list, tuple)):
-                    # one-to-many collection
+                    # one-to-many collection → list of dicts with the requested tails
                     out[root] = _serialize_collection(root_val, tails)
                 else:
                     # many-to-one or scalar dotted; place each full dotted path as key
@@ -177,6 +292,7 @@ class CRUDMixin:
                         dotted = f"{root}.{tail}"
                         out[dotted] = _deep_get_loaded(self, dotted)
 
+            # ← This was the placeholder before. We return the dict we just built.
             return out
 
         # Fallback: all mapped columns on this class hierarchy

crudkit/core/service.py

@@ -243,22 +243,32 @@ class CRUDService(Generic[T]):
         if only_cols:
             query = query.options(Load(root_alias).load_only(*only_cols))
 
-        # JOIN all resolved paths; for collections use selectinload (never join)
+        # Detect first hops that have deeper, nested tails requested (e.g. "contact.supervisor")
+        nested_first_hops = { path[0] for path in (rel_field_names or {}).keys() if len(path) > 1 }
+
         used_contains_eager = False
         for base_alias, rel_attr, target_alias in join_paths:
             is_collection = bool(getattr(getattr(rel_attr, "property", None), "uselist", False))
-            if is_collection:
+            is_nested_firsthop = rel_attr.key in nested_first_hops
+
+            if is_collection or is_nested_firsthop:
+                # Use selectinload so deeper hops can chain cleanly (and to avoid
+                # contains_eager/loader conflicts on nested paths).
                 opt = selectinload(rel_attr)
-                # narroe child columns it requested (e.g., updates.id,updates.timestamp)
-                child_names = (collection_field_names or {}).get(rel_attr.key, [])
-                if child_names:
-                    target_cls = rel_attr.property.mapper.class_
-                    cols = [getattr(target_cls, n, None) for n in child_names]
-                    cols = [c for c in cols if isinstance(c, InstrumentedAttribute)]
-                    if cols:
-                        opt = opt.load_only(*cols)
+
+                # Narrow columns for collections if we know child scalar names
+                if is_collection:
+                    child_names = (collection_field_names or {}).get(rel_attr.key, [])
+                    if child_names:
+                        target_cls = rel_attr.property.mapper.class_
+                        cols = [getattr(target_cls, n, None) for n in child_names]
+                        cols = [c for c in cols if isinstance(c, InstrumentedAttribute)]
+                        if cols:
+                            opt = opt.load_only(*cols)
+
                 query = query.options(opt)
             else:
+                # Simple first-hop scalar rel with no deeper tails: safe to join + contains_eager
                 query = query.join(target_alias, rel_attr.of_type(target_alias), isouter=True)
                 query = query.options(contains_eager(rel_attr, alias=target_alias))
                 used_contains_eager = True
@@ -453,19 +463,23 @@ class CRUDService(Generic[T]):
         if only_cols:
             query = query.options(Load(root_alias).load_only(*only_cols))
 
-        # JOIN non-collections only; collections via selectinload
+        nested_first_hops = { path[0] for path in (rel_field_names or {}).keys() if len(path) > 1 }
+
         used_contains_eager = False
         for base_alias, rel_attr, target_alias in join_paths:
             is_collection = bool(getattr(getattr(rel_attr, "property", None), "uselist", False))
-            if is_collection:
+            is_nested_firsthop = rel_attr.key in nested_first_hops
+
+            if is_collection or is_nested_firsthop:
                 opt = selectinload(rel_attr)
-                child_names = (collection_field_names or {}).get(rel_attr.key, [])
-                if child_names:
-                    target_cls = rel_attr.property.mapper.class_
-                    cols = [getattr(target_cls, n, None) for n in child_names]
-                    cols = [c for c in cols if isinstance(c, InstrumentedAttribute)]
-                    if cols:
-                        opt = opt.load_only(*cols)
+                if is_collection:
+                    child_names = (collection_field_names or {}).get(rel_attr.key, [])
+                    if child_names:
+                        target_cls = rel_attr.property.mapper.class_
+                        cols = [getattr(target_cls, n, None) for n in child_names]
+                        cols = [c for c in cols if isinstance(c, InstrumentedAttribute)]
+                        if cols:
+                            opt = opt.load_only(*cols)
                 query = query.options(opt)
             else:
                 query = query.join(target_alias, rel_attr.of_type(target_alias), isouter=True)
@@ -548,19 +562,23 @@ class CRUDService(Generic[T]):
             if only_cols:
                 query = query.options(Load(root_alias).load_only(*only_cols))
 
-            # JOIN non-collection paths; selectinload for collections
+            nested_first_hops = { path[0] for path in (rel_field_names or {}).keys() if len(path) > 1 }
+
             used_contains_eager = False
             for _base_alias, rel_attr, target_alias in join_paths:
                 is_collection = bool(getattr(getattr(rel_attr, "property", None), "uselist", False))
-                if is_collection:
+                is_nested_firsthop = rel_attr.key in nested_first_hops
+
+                if is_collection or is_nested_firsthop:
                     opt = selectinload(rel_attr)
-                    child_names = (collection_field_names or {}).get(rel_attr.key, [])
-                    if child_names:
-                        target_cls = rel_attr.property.mapper.class_
-                        cols = [getattr(target_cls, n, None) for n in child_names]
-                        cols = [c for c in cols if isinstance(c, InstrumentedAttribute)]
-                        if cols:
-                            opt = opt.load_only(*cols)
+                    if is_collection:
+                        child_names = (collection_field_names or {}).get(rel_attr.key, [])
+                        if child_names:
+                            target_cls = rel_attr.property.mapper.class_
+                            cols = [getattr(target_cls, n, None) for n in child_names]
+                            cols = [c for c in cols if isinstance(c, InstrumentedAttribute)]
+                            if cols:
+                                opt = opt.load_only(*cols)
                     query = query.options(opt)
                 else:
                     query = query.join(target_alias, rel_attr.of_type(target_alias), isouter=True)