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

crudkit/projection.py

@@ -0,0 +1,236 @@
+# crudkit/projection.py
+from __future__ import annotations
+from typing import Iterable, List, Tuple, Dict, Set
+from sqlalchemy.orm import selectinload
+from sqlalchemy.orm.attributes import InstrumentedAttribute
+from sqlalchemy.orm.properties import ColumnProperty, RelationshipProperty
+from sqlalchemy import inspect
+
+# ----------------------
+# small utilities
+# ----------------------
+
+def _is_column_attr(a) -> bool:
+    try:
+        return isinstance(a, InstrumentedAttribute) and isinstance(a.property, ColumnProperty)
+    except Exception:
+        return False
+
+def _is_relationship_attr(a) -> bool:
+    try:
+        return isinstance(a, InstrumentedAttribute) and isinstance(a.property, RelationshipProperty)
+    except Exception:
+        return False
+
+def _split_path(field: str) -> List[str]:
+    return [p for p in str(field).split(".") if p]
+
+def _model_requires_map(model_cls) -> Dict[str, List[str]]:
+    # apps declare per-model deps, e.g. {"label": ["first_name","last_name","title"]}
+    return getattr(model_cls, "__crudkit_field_requires__", {}) or {}
+
+def _relationships_of(model_cls) -> Dict[str, RelationshipProperty]:
+    try:
+        return dict(model_cls.__mapper__.relationships)
+    except Exception:
+        return {}
+
+def _attr_on(model_cls, name: str):
+    return getattr(model_cls, name, None)
+
+# ----------------------
+# EXPAND: add required deps for leaf attributes at the correct class
+# ----------------------
+
+def _expand_requires_for_field(model_cls, pieces: List[str]) -> List[str]:
+    """
+    Given a dotted path like ["owner","label"], walk relationships to the leaf *container* class,
+    pull its __crudkit_field_requires__ for that leaf attr ("label"), and yield prefixed deps:
+      owner.label -> ["owner.first_name", "owner.last_name", ...] if User requires so.
+    If leaf is a column (or has no requires), returns [].
+    """
+    if not pieces:
+        return []
+
+    # walk relationships to the leaf container (class that owns the leaf attr)
+    container_cls = model_cls
+    prefix_parts: List[str] = []
+    for part in pieces[:-1]:
+        a = _attr_on(container_cls, part)
+        if not _is_relationship_attr(a):
+            return []  # can't descend; invalid or scalar in the middle
+        container_cls = a.property.mapper.class_
+        prefix_parts.append(part)
+
+    leaf = pieces[-1]
+    requires = _model_requires_map(container_cls).get(leaf) or []
+    if not requires:
+        return []
+
+    prefix = ".".join(prefix_parts)
+    out: List[str] = []
+    for dep in requires:
+        # dep may itself be dotted relative to container (e.g. "room_function.description")
+        if prefix:
+            out.append(f"{prefix}.{dep}")
+        else:
+            out.append(dep)
+    return out
+
+def _expand_requires(model_cls, fields: Iterable[str]) -> List[str]:
+    """
+    Dedup + stable expansion of requires for all fields.
+    """
+    seen: Set[str] = set()
+    out: List[str] = []
+
+    def add(f: str):
+        if f not in seen:
+            seen.add(f)
+            out.append(f)
+
+    # first pass: add original
+    queue: List[str] = []
+    for f in fields:
+        f = str(f)
+        if f not in seen:
+            seen.add(f)
+            out.append(f)
+            queue.append(f)
+
+    # BFS-ish: when we add deps, they may trigger further deps downstream
+    while queue:
+        f = queue.pop(0)
+        deps = _expand_requires_for_field(model_cls, _split_path(f))
+        for d in deps:
+            if d not in seen:
+                seen.add(d)
+                out.append(d)
+                queue.append(d)
+
+    return out
+
+# ----------------------
+# BUILD loader options tree with selectinload + load_only on real columns
+# ----------------------
+
+def _insert_leaf(loader_tree: dict, path: List[str]):
+    """
+    Build nested dict structure keyed by relationship names.
+    Each node holds:
+      {
+        "__cols__": set(column_names_to_load_only),
+        "<child_rel>": { ... }
+      }
+    """
+    node = loader_tree
+    for rel in path[:-1]:  # only relationship hops
+        node = node.setdefault(rel, {"__cols__": set()})
+    # leaf may be a column or a virtual/hybrid; only columns go to __cols__
+    node.setdefault("__cols__", set())
+
+def _attach_column(loader_tree: dict, path: List[str], model_cls):
+    """
+    If the leaf is a real column on the target class, record its name into __cols__ at that level.
+    """
+    # descend to target class to test column-ness
+    container_cls = model_cls
+    node = loader_tree
+    for rel in path[:-1]:
+        a = _attr_on(container_cls, rel)
+        if not _is_relationship_attr(a):
+            return  # invalid path, ignore
+        container_cls = a.property.mapper.class_
+        node = node.setdefault(rel, {"__cols__": set()})
+
+    leaf = path[-1]
+    a_leaf = _attr_on(container_cls, leaf)
+    node.setdefault("__cols__", set())
+    if _is_column_attr(a_leaf):
+        node["__cols__"].add(leaf)
+
+def _build_loader_tree(model_cls, fields: Iterable[str]) -> dict:
+    """
+    For each dotted field:
+      - walk relationships -> create nodes
+      - if leaf is a column: record it for load_only
+      - if leaf is not a column (hybrid/descriptor): no load_only; still ensure rel hops exist
+    """
+    tree: Dict[str, dict] = {"__cols__": set()}
+    for f in fields:
+        parts = _split_path(f)
+        if not parts:
+            continue
+        # ensure relationship nodes exist
+        _insert_leaf(tree, parts)
+        # attach column if applicable
+        _attach_column(tree, parts, model_cls)
+    return tree
+
+def _loader_options_from_tree(model_cls, tree: dict):
+    """
+    Convert the loader tree into SQLAlchemy loader options:
+      selectinload(<rel>)[.load_only(cols)] recursively
+    """
+    opts = []
+
+    rels = _relationships_of(model_cls)
+    for rel_name, child in tree.items():
+        if rel_name == "__cols__":
+            continue
+        rel_prop = rels.get(rel_name)
+        if not rel_prop:
+            continue
+        rel_attr = getattr(model_cls, rel_name)
+        opt = selectinload(rel_attr)
+
+        # apply load_only on the related class (only real columns recorded at child["__cols__"])
+        cols = list(child.get("__cols__", []))
+        if cols:
+            rel_model = rel_prop.mapper.class_
+            # map column names to attributes
+            col_attrs = []
+            for c in cols:
+                a = getattr(rel_model, c, None)
+                if _is_column_attr(a):
+                    col_attrs.append(a)
+            if col_attrs:
+                opt = opt.load_only(*col_attrs)
+
+        # recurse to grandchildren
+        sub_opts = _loader_options_from_tree(rel_prop.mapper.class_, child)
+        for so in sub_opts:
+            opt = opt.options(so)
+
+        opts.append(opt)
+
+    # root-level columns (rare in our compile; kept for completeness)
+    root_cols = list(tree.get("__cols__", []))
+    if root_cols:
+        # NOTE: call-site can add a root load_only(...) if desired;
+        # we purposely return only relationship options here to keep
+        # the API simple and avoid mixing Load(model_cls) contexts.
+        pass
+
+    return opts
+
+# ----------------------
+# PUBLIC API
+# ----------------------
+
+def compile_projection(model_cls, fields: Iterable[str]) -> Tuple[List[str], List]:
+    """
+    Returns:
+      expanded_fields: List[str]            # original + declared dependencies
+      loader_options: List[Load]            # apply via query = query.options(*loader_options)
+
+    Behavior:
+      - Expands __crudkit_field_requires__ at the leaf container class for every field.
+      - Builds a selectinload tree; load_only only includes real columns (no hybrids).
+      - Safe for nested paths: e.g. "owner.label" pulls owner deps from User.__crudkit_field_requires__.
+    """
+    fields = list(fields or [])
+    expanded = _expand_requires(model_cls, fields)
+    tree = _build_loader_tree(model_cls, expanded)
+    options = _loader_options_from_tree(model_cls, tree)
+    return expanded, options