fix: DuckDBLazyFrame.rename using python API (#2382)

* fix: DuckDBLazyFrame.rename using python API

* rm hypothesis test

Author: FBruzzesi

narwhals/_duckdb/dataframe.py

@@ -249,11 +249,11 @@ def group_by(self: Self, *keys: str, drop_null_keys: bool) -> DuckDBGroupBy:
 
     def rename(self: Self, mapping: Mapping[str, str]) -> Self:
         df = self.native
-        selection = [
-            f"{name} as {mapping[name]}" if name in mapping else name
+        selection = (
+            col(name).alias(mapping[name]) if name in mapping else col(name)
             for name in df.columns
-        ]
-        return self._with_native(df.select(", ".join(selection)))
+        )
+        return self._with_native(self.native.select(*selection))
 
     def join(
         self: Self,

tests/frame/rename_test.py

@@ -8,6 +8,6 @@
 def test_rename(constructor: Constructor) -> None:
     data = {"a": [1, 3, 2], "b": [4, 4, 6], "z": [7.0, 8.0, 9.0]}
     df = nw.from_native(constructor(data))
-    result = df.rename({"a": "x", "b": "y"})
-    expected = {"x": [1, 3, 2], "y": [4, 4, 6], "z": [7.0, 8.0, 9.0]}
+    result = df.rename({"a": "foo-bar", "b": "foo bar"})
+    expected = {"foo-bar": [1, 3, 2], "foo bar": [4, 4, 6], "z": [7.0, 8.0, 9.0]}
     assert_equal_data(result, expected)