push_attr fixes

- don't raise exception if mods is used together with common or prefixed
  there is nothing in the logic preventing it
- don't raise if columns is used together with common or prefixed, warn
  instead
- minor code cleanup

Author: ilia-kats

src/mudata/_core/mudata.py

@@ -2242,8 +2242,6 @@ def _push_attr(
                 raise ValueError("All mods should be present in mdata.mod")
             elif len(mods) == self.n_mod:
                 mods = None
-            for k, v in {"common": common, "prefixed": prefixed}.items():
-                assert v is None, f"Cannot use mods with {k}."
 
         if only_drop:
             drop = True
@@ -2252,15 +2250,22 @@ def _push_attr(
 
         if columns is not None:
             for k, v in {"common": common, "prefixed": prefixed}.items():
-                assert v is None, f"Cannot use columns with {k}."
+                if v:
+                    warnings.warn(
+                        f"Both columns and {k} given. Columns take precedence, {k} will be ignored",
+                        RuntimeWarning,
+                        stacklevel=2,
+                    )
 
             # - modname1:column -> [modname1:column]
             # - column -> [modname1:column, modname2:column, ...]
-            cols = [col for col in cols if col["name"] in columns or col["derived_name"] in columns]
-
             # preemptively drop columns from other modalities
-            if mods is not None:
-                cols = [col for col in cols if col["prefix"] in mods or col["prefix"] == ""]
+            cols = [
+                col
+                for col in cols
+                if (col["name"] in columns or col["derived_name"] in columns)
+                and (col["prefix"] == "" or mods is not None and col["prefix"] in mods)
+            ]
         else:
             if common is None:
                 common = True

src/mudata/_core/utils.py

@@ -122,30 +122,17 @@ def _classify_prefixed_columns(
     res: list[dict[str, str]] = []
 
     for name in names:
-        name_common = {
-            "name": name,
-            "prefix": "",
-            "derived_name": name,
-        }
-        name_split = name.split(":", 1)
-
-        if len(name_split) < 2:
-            res.append(name_common)
+        if len(name_split := name.split(":", 1)) < 2 or name_split[0] not in prefixes:
+            res.append({"name": name, "prefix": "", "derived_name": name, "class": "common"})
         else:
-            maybe_modname, derived_name = name_split
-
-            if maybe_modname in prefixes:
-                name_prefixed = {
+            res.append(
+                {
                     "name": name,
-                    "prefix": maybe_modname,
-                    "derived_name": derived_name,
+                    "prefix": name_split[0],
+                    "derived_name": name_split[1],
+                    "class": "prefixed",
                 }
-                res.append(name_prefixed)
-            else:
-                res.append(name_common)
-
-    for name_res in res:
-        name_res["class"] = "common" if name_res["prefix"] == "" else "prefixed"
+            )
 
     return res