Add crudkit!

crudkit/eager.py

@@ -0,0 +1,42 @@
+from typing import List
+from sqlalchemy.inspection import inspect
+from sqlalchemy.orm import Load, joinedload, selectinload
+
+def default_eager_policy(Model, expand: List[str]) -> List[Load]:
+    """
+    Heuristic:
+      - many-to-one / one-to-one: joinedload
+      - one-to-many / many-to-many: selectinload
+    Accepts dotted paths like "author.publisher".
+    """
+    if not expand:
+        return []
+
+    opts: List[Load] = []
+
+    for path in expand:
+        parts = path.split(".")
+        current_model = Model
+        current_inspect = inspect(current_model)
+
+        # first hop
+        rel = current_inspect.relationships.get(parts[0])
+        if not rel:
+            continue  # silently skip bad names
+        attr = getattr(current_model, parts[0])
+        loader: Load = selectinload(attr) if rel.uselist else joinedload(attr)
+        current_model = rel.mapper.class_
+
+        # nested hops, if any
+        for name in parts[1:]:
+            current_inspect = inspect(current_model)
+            rel = current_inspect.relationships.get(name)
+            if not rel:
+                break
+            attr = getattr(current_model, name)
+            loader = loader.selectinload(attr) if rel.uselist else loader.joinedload(attr)
+            current_model = rel.mapper.class_
+
+        opts.append(loader)
+
+    return opts