[c-api] check number of features when retrieving number of bins (micr…

…osoft#5183)

* check number of features when retrieving number of bins

* check for negative values

* lint

src/c_api.cpp

@@ -1555,6 +1555,11 @@ int LGBM_DatasetGetFeatureNumBin(DatasetHandle handle,
                                  int* out) {
   API_BEGIN();
   auto dataset = reinterpret_cast<Dataset*>(handle);
+  int num_features = dataset->num_total_features();
+  if (feature < 0 || feature >= num_features) {
+    Log::Fatal("Tried to retrieve number of bins for feature index %d, "
+               "but the valid feature indices are [0, %d].", feature, num_features - 1);
+  }
   int inner_idx = dataset->InnerFeatureIndex(feature);
   if (inner_idx >= 0) {
     *out = dataset->FeatureNumBin(inner_idx);

tests/python_package_test/test_basic.py

@@ -674,6 +674,16 @@ def test_feature_num_bin(min_data_in_bin):
     ]
     actual_num_bins = [ds.feature_num_bin(i) for i in range(X.shape[1])]
     assert actual_num_bins == expected_num_bins
+    # check for feature indices outside of range
+    num_features = X.shape[1]
+    with pytest.raises(
+        lgb.basic.LightGBMError,
+        match=(
+            f'Tried to retrieve number of bins for feature index {num_features}, '
+            f'but the valid feature indices are \\[0, {num_features - 1}\\].'
+        )
+    ):
+        ds.feature_num_bin(num_features)
 
 
 def test_feature_num_bin_with_max_bin_by_feature():