More field and form rendering logic.

crudkit/ui/fragments.py

@@ -26,6 +26,24 @@ def get_env():
         loader=ChoiceLoader([app.jinja_loader, fallback_loader])
     )
 
+def _get_loaded_attr(obj: Any, name: str) -> Any:
+    """
+    Return obj.<name> only if it is already loaded.
+    Never triggers a lazy load. Returns None if missing/unloaded.
+    Works for both column and relationship attributes.
+    """
+    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 getattr(obj, name, None)
+    except Exception:
+        return getattr(obj, name, None)
+
 def _normalize_rows_layout(layout: Optional[List[dict]]) -> Dict[str, dict]:
     """
     Create node dicts for each row and link parent->children.
@@ -173,6 +191,69 @@ def _sanitize_attrs(attrs: Any) -> dict[str, Any]:
 
     return out
 
+def _resolve_rel_obj(values: dict, instance, base: str):
+    rel = None
+    if isinstance(values, dict) and base in values:
+        rel = values[base]
+        if isinstance(rel, dict):
+            class _DictObj:
+                def __init__(self, d): self._d = d
+                def __getattr__(self, k): return self._d.get(k)
+            rel = _DictObj(rel)
+
+    if rel is None and instance is not None:
+        try:
+            st = inspect(instance)
+            ra = st.attrs.get(base)
+            if ra is not None and ra.loaded_value is not NO_VALUE:
+                rel  = ra.loaded_value
+        except Exception:
+            pass
+
+    return rel
+
+def _value_label_for_field(field: dict, mapper, values_map: dict, instance, session):
+    """
+    If field targets a MANYTOONE (foo or foo_id), compute a human-readable label.
+    No lazy loads. Optional single-row lean fetch if we only have the id.
+    """
+    base, rel_prop = _rel_for_id_name(mapper, field["name"])
+    if not rel_prop:
+        return None
+
+    rid = _coerce_fk_value(values_map, instance, base)
+    rel_obj = _resolve_rel_obj(values_map, instance, base)
+
+    label_spec = (
+        field.get("label_spec")
+        or getattr(rel_prop.mapper.class_, "__crud_label__", None)
+        or "id"
+    )
+
+    if rel_obj is not None and not _has_label_bits_loaded(rel_obj, label_spec) and session is not None and rid is not None:
+            mdl = rel_prop.mapper.class_
+            simple_cols, rel_paths = _extract_label_requirements(label_spec)
+            q = session.query(mdl)
+            cols = [getattr(mdl, "id")]
+            for c in simple_cols:
+                if hasattr(mdl, c):
+                    cols.append(getattr(mdl, c))
+            if cols:
+                q = q.options(load_only(*cols))
+            for rel_name, col_name in rel_paths:
+                try:
+                    t_rel = mdl.__mapper__.relationships[rel_name]
+                    t_cls = t_rel.mapper.class_
+                    col_attr = getattr(t_cls, col_name, None)
+                    opt = selectinload(getattr(mdl, rel_name))
+                    q = q.options(opt.load_only(col_attr) if col_attr is not None else opt)
+                except Exception:
+                    q = q.options(selectinload(getattr(mdl, rel_name)))
+            rel_obj = q.get(rid)
+    if rel_obj is not None:
+        return _label_from_obj(rel_obj, label_spec)
+    return str(rid) if rid is not None else None
+
 class _SafeObj:
     """Attribute access that returns '' for missing/None instead of exploding."""
     __slots__ = ("_obj",)
@@ -181,10 +262,8 @@ class _SafeObj:
     def __getattr__(self, name):
         if self._obj is None:
             return ""
-        val = getattr(self._obj, name, None)
+        val = _get_loaded_attr(self._obj, name)
-        if val is None:
+        return "" if val is None else _SafeObj(val)
-            return ""
-        return _SafeObj(val)
 
 def _coerce_fk_value(values: dict | None, instance: Any, base: str):
     """
@@ -314,6 +393,7 @@ def _normalize_field_spec(spec, mapper, session, label_specs_model_default):
         "template": spec.get("template"),
         "template_name": spec.get("template_name"),
         "template_ctx": spec.get("template_ctx"),
+        "label_spec": spec.get("label_spec")
     }
 
     if rel_prop:
@@ -387,41 +467,24 @@ def _extract_label_requirements(spec: Any) -> tuple[list[str], list[tuple[str, s
 
     return simple_cols, rel_paths
 
-def _attrs_from_label_spec(spec: Any) -> list[str]:
-    """
-    Return a list of attribute names needed from the related model to compute the label.
-    Only simple attribute names are returned; dotted paths return just the first segment.
-    """
-    if spec is None:
-        return []
-    if callable(spec):
-        return []
-    if isinstance(spec, (list, tuple)):
-        return [str(a).split(".", 1)[0] for a in spec]
-    if isinstance(spec, str):
-        if "{" in spec and "}" in spec:
-            names = re.findall(r"{\s*([^}:\s]+)", spec)
-            return [n.split(".", 1)[0] for n in names]
-        return [spec.split(".", 1)[0]]
-    return []
-
 def _label_from_obj(obj: Any, spec: Any) -> str:
+    if obj is None:
+        return ""
+
     if spec is None:
         for attr in ("label", "name", "title", "description"):
-            if hasattr(obj, attr):
+            val = _get_loaded_attr(obj, attr)
-                val = getattr(obj, attr)
+            if val is not None:
-                if not callable(val) and val is not None:
+                return str(val)
-                    return str(val)
+        vid = _get_loaded_attr(obj, "id")
-        if hasattr(obj, "id"):
+        return str(vid) if vid is not None else object.__repr__(obj)
-            return str(getattr(obj, "id"))
-        return object.__repr__(obj)
 
     if isinstance(spec, (list, tuple)):
         parts = []
         for a in spec:
             cur = obj
             for part in str(a).split("."):
-                cur = getattr(cur, part, None)
+                cur = _get_loaded_attr(cur, part) if cur is not None else None
                 if cur is None:
                     break
             parts.append("" if cur is None else str(cur))
@@ -433,9 +496,7 @@ def _label_from_obj(obj: Any, spec: Any) -> str:
         for f in fields:
             root = f.split(".", 1)[0]
             if root not in data:
-                val = getattr(obj, root, None)
+                data[root] = _SafeObj(_get_loaded_attr(obj, root))
-                data[root] = _SafeObj(val)
-
         try:
             return spec.format(**data)
         except Exception:
@@ -443,7 +504,7 @@ def _label_from_obj(obj: Any, spec: Any) -> str:
 
     cur = obj
     for part in str(spec).split("."):
-        cur = getattr(cur, part, None)
+        cur = _get_loaded_attr(cur, part) if cur is not None else None
         if cur is None:
             return ""
     return str(cur)
@@ -572,6 +633,28 @@ def _format_value(val: Any, fmt: Optional[str]) -> Any:
         return val
     return val
 
+def _has_label_bits_loaded(obj: Any, label_spec: Any) -> bool:
+    try:
+        st = inspect(obj)
+    except Exception:
+        return True
+
+    simple_cols, rel_paths = _extract_label_requirements(label_spec)
+    for c in simple_cols:
+        if c not in st.dict:
+            return False
+    for rel, col in rel_paths:
+        ra = st.attrs.get(rel)
+        if ra is None or ra.loaded_value is NO_VALUE or ra.loaded_value is None:
+            return False
+        try:
+            t_st = inspect(ra.loaded_value)
+            if col not in t_st.dict:
+                return False
+        except Exception:
+            return False
+    return True
+
 def _class_for(val: Any, classes: Optional[Dict[str, str]]) -> Optional[str]:
     if not classes:
         return None
@@ -642,6 +725,7 @@ def get_crudkit_template(env, name):
 
 def render_field(field, value):
     env = get_env()
+    print(field)
 
     # 1) custom template field
     field_type = field.get('type', 'text')
@@ -668,6 +752,7 @@ def render_field(field, value):
         attrs=_sanitize_attrs(field.get('attrs') or {}),
         label_attrs=_sanitize_attrs(field.get('label_attrs') or {}),
         help=field.get('help'),
+        value_label=field.get('value_label'),
     )
 
 
@@ -825,6 +910,11 @@ def render_form(
                 base.update(f.get("template_ctx") or {})
                 f["template_ctx"] = base
 
+    for f in fields:
+        vl = _value_label_for_field(f, mapper, values_map, instance, session)
+        if vl is not None:
+            f["value_label"] = vl
+
     # Build rows (supports nested layout with parents)
     rows_map = _normalize_rows_layout(layout)
     rows_tree = _assign_fields_to_rows(fields, rows_map)

crudkit/ui/templates/field.html

@@ -30,7 +30,7 @@
   <textarea name="{{ field_name }}" id="{{ field_name }}"
             {% if attrs %}{% for k,v in attrs.items() %}
               {{k}}{% if v is not sameas true %}="{{ v }}"{% endif %}
-            {% endfor %}{% endif %}>{{ value }}</textarea>
+            {% endfor %}{% endif %}>{{ value if value else "" }}</textarea>
 
 {% elif field_type == 'checkbox' %}
   <input type="checkbox" name="{{ field_name }}" id="{{ field_name }}" value="1"
@@ -40,15 +40,15 @@
          {% endfor %}{% endif %}>
 
 {% elif field_type == 'hidden' %}
-  <input type="hidden" name="{{ field_name }}" id="{{ field_name }}" value="{{ value }}">
+  <input type="hidden" name="{{ field_name }}" id="{{ field_name }}" value="{{ value if value else "" }}">
 
 {% elif field_type == 'display' %}
   <div {% if attrs %}{% for k,v in attrs.items() %}
          {{k}}{% if v is not sameas true %}="{{ v }}"{% endif %}
-       {% endfor %}{% endif %}>{{ value }}</div>
+       {% endfor %}{% endif %}>{{ value_label if value_label else (value if value else "") }}</div>
 
 {% else %}
-  <input type="text" name="{{ field_name }}" id="{{ field_name }}" value="{{ value }}"
+  <input type="text" name="{{ field_name }}" id="{{ field_name }}" value="{{ value if value else "" }}"
          {% if attrs %}{% for k,v in attrs.items() %}
            {{k}}{% if v is not sameas true %}="{{ v }}"{% endif %}
          {% endfor %}{% endif %}>