From dd6c8de3787cf9238fd6bcb8d654452a55288519 Mon Sep 17 00:00:00 2001
From: Tomasz Kalinowski <kalinowskit@gmail.com>
Date: Fri, 7 Mar 2025 08:28:52 -0500
Subject: [PATCH] fix coerce in `py_slice()`

---
 src/python.cpp                               | 28 ++++++++++++++------
 tests/testthat/test-python-base-r-generics.R |  2 +-
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/src/python.cpp b/src/python.cpp
index cbdd0242..fccded54 100644
--- a/src/python.cpp
+++ b/src/python.cpp
@@ -4619,22 +4619,34 @@ PyObjectRef py_capsule(SEXP x) {
 PyObjectRef py_slice(SEXP start = R_NilValue, SEXP stop = R_NilValue, SEXP step = R_NilValue) {
   GILScope _gil;
 
-  PyObjectPtr start_, stop_, step_;
+  auto coerce_slice_arg = [](SEXP x) -> PyObject* {
+    if (x == R_NilValue) {
+      return NULL;
+    }
+    if (TYPEOF(x) == INTSXP || TYPEOF(x) == REALSXP) {
+      return PyLong_FromLong(Rf_asInteger(x));
+    }
+    if (is_py_object(x)) {
+      PyObject* pyobj = PyObjectRef(x, false).get();
+      Py_IncRef(pyobj);
+      return pyobj;
+    }
+    return r_to_py(x, false);
+  };
 
-  if (start != R_NilValue)
-    start_.assign(PyLong_FromLong(Rf_asInteger(start)));
-  if (stop != R_NilValue)
-    stop_.assign(PyLong_FromLong(Rf_asInteger(stop)));
-  if (step != R_NilValue)
-    step_.assign(PyLong_FromLong(Rf_asInteger(step)));
+  PyObjectPtr start_(coerce_slice_arg(start));
+  PyObjectPtr  stop_(coerce_slice_arg(stop));
+  PyObjectPtr  step_(coerce_slice_arg(step));
 
-  PyObject* out(PySlice_New(start_, stop_, step_));
+  PyObject* out = PySlice_New(start_, stop_, step_);
   if (out == NULL)
     throw PythonException(py_fetch_error());
+
   return py_ref(out, false);
 }
 
 
+
 //' @rdname iterate
 //' @export
 // [[Rcpp::export]]
diff --git a/tests/testthat/test-python-base-r-generics.R b/tests/testthat/test-python-base-r-generics.R
index c2858786..c011d492 100644
--- a/tests/testthat/test-python-base-r-generics.R
+++ b/tests/testthat/test-python-base-r-generics.R
@@ -173,7 +173,7 @@ test_that("[ can infer slices, multiple args", {
 
 test_that("[ passes through python objects", {
 
-  skip_if_no_numpy("numpy")
+  skip_if_no_numpy()
 
   np <- import("numpy", convert = FALSE)