test(e2e): cover nanobind_extension against the PBS py_cc toolchain

e2e/cases/MODULE.bazel

@@ -9,6 +9,7 @@ bazel_dep(name = "tar.bzl", version = "0.10.1")
 bazel_dep(name = "rules_python", version = "1.9.0")
 bazel_dep(name = "platforms", version = "1.0.0")
 bazel_dep(name = "llvm", version = "0.8.3")
+bazel_dep(name = "nanobind_bazel", version = "2.12.0")
 bazel_dep(name = "rules_oci", version = "2.2.7")
 bazel_dep(name = "rules_rust", version = "0.68.1")
 bazel_dep(name = "rules_shell", version = "0.4.1")

e2e/cases/nanobind-py-cc/BUILD.bazel

@@ -0,0 +1,44 @@
+load("@aspect_rules_py//py:defs.bzl", "py_test")
+load("@bazel_skylib//rules:build_test.bzl", "build_test")
+load("@nanobind_bazel//:build_defs.bzl", "nanobind_extension")
+
+# Regression coverage for https://github.com/aspect-build/rules_py/issues/1095.
+#
+# `python_interpreters` is positioned as a drop-in for rules_python's
+# `python.toolchain()`. For native Python extensions to build, it must register a
+# `@rules_python//python/cc:toolchain_type` (py_cc) toolchain over the PBS
+# interpreter: nanobind and pybind11 resolve their Python headers through
+# `@rules_python//python/cc:current_py_cc_headers`, which consumes that toolchain
+# type. Before the registration landed, analysis of any nanobind_extension in a
+# graph whose only Python toolchains come from `python_interpreters` failed with:
+#
+#   No matching toolchains found for types:
+#     @@rules_python+//python/cc:toolchain_type
+#
+# `pbs-cc-toolchain` already covers the bare `cc_binary` + `current_py_cc_headers`
+# / `current_py_cc_libs` path. This case adds coverage for the nanobind consumer,
+# which is how most real-world native extensions reach `current_py_cc_headers`.
+
+nanobind_extension(
+    name = "example_ext",
+    srcs = ["example_ext.cpp"],
+)
+
+# Core guard: a nanobind_extension only *analyzes* if python_interpreters
+# registers the py_cc toolchain. This build_test fails at analysis otherwise,
+# regardless of runtime import-path details.
+build_test(
+    name = "example_ext_build_test",
+    targets = [":example_ext"],
+)
+
+# End-to-end: compile + link + load + call the extension under a PBS runtime.
+py_test(
+    name = "example_ext_test",
+    size = "small",
+    srcs = ["example_ext_test.py"],
+    imports = ["."],  # put this package dir on sys.path so `import example_ext` finds the .so
+    main = "example_ext_test.py",
+    python_version = "3.13",
+    deps = [":example_ext"],
+)

e2e/cases/nanobind-py-cc/example_ext.cpp

@@ -0,0 +1,12 @@
+#include <nanobind/nanobind.h>
+#include <nanobind/stl/string.h>
+
+// A minimal nanobind extension. nanobind resolves the Python headers it needs
+// through @rules_python//python/cc:current_py_cc_headers, which consumes the
+// @rules_python//python/cc:toolchain_type (py_cc) toolchain. In a graph whose
+// only Python toolchains come from python_interpreters, that toolchain must be
+// registered by python_interpreters itself or this fails to build (issue #1095).
+NB_MODULE(example_ext, m) {
+    m.def("add", [](int a, int b) { return a + b; });
+    m.def("greet", [](const std::string &name) { return "Hello, " + name + "!"; });
+}

e2e/cases/nanobind-py-cc/example_ext_test.py

@@ -0,0 +1,6 @@
+import example_ext
+
+assert example_ext.add(2, 3) == 5, example_ext.add(2, 3)
+assert example_ext.greet("World") == "Hello, World!", example_ext.greet("World")
+
+print("nanobind extension imported and called successfully")