From 98e42ccc9194ed03de8a2b104167faa63fc49fcd Mon Sep 17 00:00:00 2001
From: ritchie <ritchie46@gmail.com>
Date: Fri, 18 Oct 2024 10:27:28 +0200
Subject: [PATCH] fix: Fix struct reshape fast path

---
 crates/polars-core/src/series/ops/reshape.rs      | 15 +++++----------
 .../unit/operations/namespaces/list/test_list.py  | 15 +++++++++++++++
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/crates/polars-core/src/series/ops/reshape.rs b/crates/polars-core/src/series/ops/reshape.rs
index 642faafbfdf8..3bf4898c5bc7 100644
--- a/crates/polars-core/src/series/ops/reshape.rs
+++ b/crates/polars-core/src/series/ops/reshape.rs
@@ -12,16 +12,11 @@ use crate::datatypes::{DataType, ListChunked};
 use crate::prelude::{IntoSeries, Series, *};
 
 fn reshape_fast_path(name: PlSmallStr, s: &Series) -> Series {
-    let mut ca = match s.dtype() {
-        #[cfg(feature = "dtype-struct")]
-        DataType::Struct(_) => {
-            ListChunked::with_chunk(name, array_to_unit_list(s.array_ref(0).clone()))
-        },
-        _ => ListChunked::from_chunk_iter(
-            name,
-            s.chunks().iter().map(|arr| array_to_unit_list(arr.clone())),
-        ),
-    };
+    let mut ca = ListChunked::from_chunk_iter(
+        name,
+        s.chunks().iter().map(|arr| array_to_unit_list(arr.clone())),
+    );
+
     ca.set_inner_dtype(s.dtype().clone());
     ca.set_fast_explode();
     ca.into_series()
diff --git a/py-polars/tests/unit/operations/namespaces/list/test_list.py b/py-polars/tests/unit/operations/namespaces/list/test_list.py
index 966fee3ea5ac..dfe6adad08d0 100644
--- a/py-polars/tests/unit/operations/namespaces/list/test_list.py
+++ b/py-polars/tests/unit/operations/namespaces/list/test_list.py
@@ -885,3 +885,18 @@ def test_list_get_with_null() -> None:
 def test_list_sum_bool_schema() -> None:
     q = pl.LazyFrame({"x": [[True, True, False]]})
     assert q.select(pl.col("x").list.sum()).collect_schema()["x"] == pl.UInt32
+
+
+def test_list_concat_struct_19279() -> None:
+    df = pl.select(
+        pl.struct(s=pl.lit("abcd").str.split("").explode(), i=pl.int_range(0, 4))
+    )
+    df = pl.concat([df[:2], df[-2:]])
+    assert df.select(pl.concat_list("s")).to_dict(as_series=False) == {
+        "s": [
+            [{"s": "a", "i": 0}],
+            [{"s": "b", "i": 1}],
+            [{"s": "c", "i": 2}],
+            [{"s": "d", "i": 3}],
+        ]
+    }