feat: improve error message on check_columns_exist (#1799)

* improve check column exists message

* remove join

* order missing

narwhals/utils.py

@@ -1062,6 +1062,6 @@ def generate_repr(header: str, native_repr: str) -> str:
 
 
 def check_column_exists(columns: list[str], subset: list[str] | None) -> None:
-    if subset is not None and any(x not in columns for x in subset):
-        msg = f"Column(s) {subset} not found in {columns}"
+    if subset is not None and (missing := set(subset).difference(columns)):
+        msg = f"Column(s) {sorted(missing)} not found in {columns}"
         raise ColumnNotFoundError(msg)

tests/utils_test.py

@@ -291,9 +291,9 @@ def test_parse_version(version: str, expected: tuple[int, ...]) -> None:
 
 def test_check_column_exists() -> None:
     columns = ["a", "b", "c"]
-    subset = ["a", "d"]
+    subset = ["d", "f"]
     with pytest.raises(
         ColumnNotFoundError,
-        match=re.escape("Column(s) ['a', 'd'] not found in ['a', 'b', 'c']"),
+        match=re.escape("Column(s) ['d', 'f'] not found in ['a', 'b', 'c']"),
     ):
         check_column_exists(columns, subset)