fix(rust): Prevent panic on sample_n with replacement from empty df (#…

…10731)

crates/polars-core/src/chunked_array/random.rs

@@ -9,6 +9,9 @@ use crate::random::get_global_random_u64;
 use crate::utils::{CustomIterTools, NoNull};
 
 fn create_rand_index_with_replacement(n: usize, len: usize, seed: Option<u64>) -> IdxCa {
+    if len == 0 {
+        return IdxCa::new_vec("", vec![]);
+    }
     let mut rng = SmallRng::seed_from_u64(seed.unwrap_or_else(get_global_random_u64));
     let dist = Uniform::new(0, len as IdxSize);
     (0..n as IdxSize)

py-polars/tests/unit/operations/test_random.py

@@ -54,6 +54,19 @@ def test_sample_df() -> None:
     assert df.sample(fraction=0.4, seed=0).shape == (1, 3)
 
 
+def test_sample_empty_df() -> None:
+    df = pl.DataFrame({"foo": []})
+
+    # // If with replacement, then expect empty df
+    assert df.sample(n=3, with_replacement=True).shape == (0, 1)
+    assert df.sample(fraction=0.4, with_replacement=True).shape == (0, 1)
+
+    # // If without replacement, then expect shape mismatch on sample_n not sample_frac
+    with pytest.raises(pl.ShapeError):
+        df.sample(n=3, with_replacement=False)
+    assert df.sample(fraction=0.4, with_replacement=False).shape == (0, 1)
+
+
 def test_sample_series() -> None:
     s = pl.Series("a", [1, 2, 3, 4, 5])