From 463536e15c2b26da7d9ed7ba5d46fd1c47dd7d5e Mon Sep 17 00:00:00 2001
From: Marco Gorelli <33491632+MarcoGorelli@users.noreply.github.com>
Date: Tue, 20 Feb 2024 18:05:04 +0000
Subject: [PATCH] dont increase depth for alias close #1

---
 narwhals/pandas_like/__init__.py | 4 ++--
 narwhals/utils.py                | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/narwhals/pandas_like/__init__.py b/narwhals/pandas_like/__init__.py
index 953c56966..a2ff11535 100644
--- a/narwhals/pandas_like/__init__.py
+++ b/narwhals/pandas_like/__init__.py
@@ -354,13 +354,13 @@ def sample(self, n: int, fraction: float, *, with_replacement: bool) -> ExprT:
 
     def alias(self, name: str) -> ExprT:
         # Define this one manually, so that we can
-        # override `output_names`
+        # override `output_names` and not increase depth
         if self._depth is None:
             msg = "Unreachable code, please report a bug"
             raise AssertionError(msg)
         return Expr(
             lambda df: [series.alias(name) for series in self.call(df)],
-            depth=self._depth + 1,
+            depth=self._depth,
             function_name=self._function_name,
             root_names=self._root_names,
             output_names=[name],
diff --git a/narwhals/utils.py b/narwhals/utils.py
index 942599dae..e5078109a 100644
--- a/narwhals/utils.py
+++ b/narwhals/utils.py
@@ -229,7 +229,7 @@ def is_simple_aggregation(expr: Expr) -> bool:
     return (
         expr._function_name is not None  # type: ignore[attr-defined]
         and expr._depth is not None  # type: ignore[attr-defined]
-        and expr._depth <= 2  # type: ignore[attr-defined]
+        and expr._depth < 2  # type: ignore[attr-defined]
         # todo: avoid this one?
         and expr._root_names is not None  # type: ignore[attr-defined]
     )