fix: Incorrect broadcasting on list-of-string set ops (#18918)

crates/polars-ops/src/chunked_array/list/sets.rs

@@ -303,7 +303,10 @@ fn binary(
         let offset = if broadcast_rhs {
             // going via skip iterator instead of slice doesn't heap alloc nor trigger a bitcount
             let a_iter = a.into_iter().skip(start_a).take(end_a - start_a);
-            let b_iter = b.into_iter();
+            let b_iter = b
+                .into_iter()
+                .skip(first_b as usize)
+                .take(second_b as usize - first_b as usize);
             set_operation(
                 &mut set,
                 &mut set2,
@@ -314,7 +317,10 @@ fn binary(
                 true,
             )
         } else if broadcast_lhs {
-            let a_iter = a.into_iter();
+            let a_iter = a
+                .into_iter()
+                .skip(first_a as usize)
+                .take(second_a as usize - first_a as usize);
             let b_iter = b.into_iter().skip(start_b).take(end_b - start_b);
             set_operation(
                 &mut set,

py-polars/tests/unit/operations/namespaces/list/test_set_operations.py

@@ -163,6 +163,28 @@ def test_list_set_operations_binary() -> None:
     ]
 
 
+def test_list_set_operations_broadcast_binary() -> None:
+    df = pl.DataFrame(
+        {
+            "a": [["2", "3", "3"], ["3", "1"], ["1", "2", "3"]],
+            "b": [["1", "2"], ["4"], ["5"]],
+        }
+    )
+
+    assert df.select(pl.col("a").list.set_intersection(pl.col.b.first())).to_dict(
+        as_series=False
+    ) == {"a": [["2"], ["1"], ["1", "2"]]}
+    assert df.select(pl.col("a").list.set_union(pl.col.b.first())).to_dict(
+        as_series=False
+    ) == {"a": [["2", "3", "1"], ["3", "1", "2"], ["1", "2", "3"]]}
+    assert df.select(pl.col("a").list.set_difference(pl.col.b.first())).to_dict(
+        as_series=False
+    ) == {"a": [["3"], ["3"], ["3"]]}
+    assert df.select(pl.col.b.first().list.set_difference("a")).to_dict(
+        as_series=False
+    ) == {"b": [["1"], ["2"], []]}
+
+
 def test_set_operations_14290() -> None:
     df = pl.DataFrame(
         {