MAINT Parameters validation for sklearn.utils.gen_even_slices (scikit-learn#26682)

Co-authored-by: Guillaume Lemaitre <g.lemaitre58@gmail.com>

Author: Charlie-XIAO

sklearn/tests/test_public_functions.py

@@ -307,6 +307,8 @@ def _check_function_param_validation(
     "sklearn.tree.export_text",
     "sklearn.tree.plot_tree",
     "sklearn.utils.gen_batches",
+    "sklearn.utils.gen_even_slices",
+    "sklearn.utils.graph.single_source_shortest_path_length",
     "sklearn.utils.resample",
     "sklearn.utils.safe_mask",
     "sklearn.utils.extmath.randomized_svd",

sklearn/utils/__init__.py

@@ -19,7 +19,7 @@
 from . import _joblib, metadata_routing
 from ._bunch import Bunch
 from ._estimator_html_repr import estimator_html_repr
-from ._param_validation import Interval, validate_params
+from ._param_validation import Integral, Interval, validate_params
 from .class_weight import compute_class_weight, compute_sample_weight
 from .deprecation import deprecated
 from .discovery import all_estimators
@@ -796,6 +796,14 @@ def gen_batches(n, batch_size, *, min_batch_size=0):
         yield slice(start, n)
 
 
+@validate_params(
+    {
+        "n": [Interval(Integral, 1, None, closed="left")],
+        "n_packs": [Interval(Integral, 1, None, closed="left")],
+        "n_samples": [Interval(Integral, 1, None, closed="left"), None],
+    },
+    prefer_skip_nested_validation=True,
+)
 def gen_even_slices(n, n_packs, *, n_samples=None):
     """Generator to create `n_packs` evenly spaced slices going up to `n`.
 
@@ -835,8 +843,6 @@ def gen_even_slices(n, n_packs, *, n_samples=None):
     [slice(0, 4, None), slice(4, 7, None), slice(7, 10, None)]
     """
     start = 0
-    if n_packs < 1:
-        raise ValueError("gen_even_slices got n_packs=%s, must be >=1" % n_packs)
     for pack_num in range(n_packs):
         this_n = n // n_packs
         if pack_num < n % n_packs:

sklearn/utils/tests/test_utils.py

@@ -545,11 +545,6 @@ def test_gen_even_slices():
     joined_range = list(chain(*[some_range[slice] for slice in gen_even_slices(10, 3)]))
     assert_array_equal(some_range, joined_range)
 
-    # check that passing negative n_chunks raises an error
-    slices = gen_even_slices(10, -1)
-    with pytest.raises(ValueError, match="gen_even_slices got n_packs=-1, must be >=1"):
-        next(slices)
-
 
 @pytest.mark.parametrize(
     ("row_bytes", "max_n_rows", "working_memory", "expected"),