REGR: fix bug in apply when returning a series (#2286)

Author: m-richards

geopandas/geodataframe.py

@@ -1408,7 +1408,10 @@ def apply(self, func, axis=0, raw=False, result_type=None, args=(), **kwargs):
             func, axis=axis, raw=raw, result_type=result_type, args=args, **kwargs
         )
         # Reconstruct gdf if it was lost by apply
-        if self._geometry_column_name in result.columns:
+        if (
+            isinstance(result, DataFrame)
+            and self._geometry_column_name in result.columns
+        ):
             # axis=1 apply will split GeometryDType to object, try and cast back
             try:
                 result = result.set_geometry(self._geometry_column_name)

geopandas/tests/test_pandas_methods.py

@@ -652,6 +652,15 @@ def test_apply_preserves_geom_col_name(df):
     assert result.geometry.name == "geom"
 
 
+def test_df_apply_returning_series(df):
+    # https://github.com/geopandas/geopandas/issues/2283
+    result = df.apply(lambda row: row.geometry, axis=1)
+    assert_geoseries_equal(result, df.geometry, check_crs=False)
+
+    result = df.apply(lambda row: row.value1, axis=1)
+    assert_series_equal(result, df["value1"].rename(None))
+
+
 @pytest.mark.skipif(not compat.PANDAS_GE_10, reason="attrs introduced in pandas 1.0")
 def test_preserve_attrs(df):
     # https://github.com/geopandas/geopandas/issues/1654