BUG: Join ValueError for DataFrame list

doc/source/whatsnew/v1.5.0.rst

@@ -619,6 +619,7 @@ Styler
 
 Other
 ^^^^^
+- Bug in :meth:`DataFrame.join` with a list when using suffixes to join DataFrames with duplicate column names (:issue:`46396`)
 
 .. ***DO NOT USE THIS SECTION***
 

pandas/core/frame.py

@@ -9576,6 +9576,11 @@ def _join_compat(
                     "Joining multiple DataFrames only supported for joining on index"
                 )
 
+            if rsuffix or lsuffix:
+                raise ValueError(
+                    "Suffixes not supported when joining multiple DataFrames"
+                )
+
             frames = [self] + list(other)
 
             can_concat = all(df.index.is_unique for df in frames)

pandas/tests/frame/methods/test_join.py

@@ -82,6 +82,28 @@ def test_join(left, right, how, sort, expected):
     tm.assert_frame_equal(result, expected)
 
 
+def test_suffix_on_list_join():
+    first = DataFrame({"key": [1, 2, 3, 4, 5]})
+    second = DataFrame({"key": [1, 8, 3, 2, 5], "v1": [1, 2, 3, 4, 5]})
+    third = DataFrame({"keys": [5, 2, 3, 4, 1], "v2": [1, 2, 3, 4, 5]})
+
+    # check proper errors are raised
+    msg = "Suffixes not supported when joining multiple DataFrames"
+    with pytest.raises(ValueError, match=msg):
+        first.join([second], lsuffix="y")
+    with pytest.raises(ValueError, match=msg):
+        first.join([second, third], rsuffix="x")
+    with pytest.raises(ValueError, match=msg):
+        first.join([second, third], lsuffix="y", rsuffix="x")
+    with pytest.raises(ValueError, match="Indexes have overlapping values"):
+        first.join([second, third])
+
+    # no errors should be raised
+    arr_joined = first.join([third])
+    norm_joined = first.join(third)
+    tm.assert_frame_equal(arr_joined, norm_joined)
+
+
 def test_join_index(float_frame):
     # left / right