Expose nanobind's stubgen as a py_binary

Adds `typing_extensions` as a unconditional dependency
for the stubgen target.

The plan is to wrap the py_binary into a nanobind stubgen
rule that lives in the same file as all other rules.

BUILD

@@ -149,3 +149,10 @@ selects.config_setting_group(
         ":with_sizeopts",
     ],
 )
+
+py_binary(
+    name = "nanobind_stubgen",
+    srcs = ["@nanobind//:src/stubgen.py"],
+    main = "@nanobind//:src/stubgen.py",
+    deps = ["@pypi__typing_extensions//:lib"],
+)

MODULE.bazel

@@ -11,4 +11,4 @@ bazel_dep(name = "bazel_skylib", version = "1.6.1")
 
 # Creates a `http_archive` for nanobind and robin-map.
 internal_configure = use_extension("//:internal_configure.bzl", "internal_configure_extension")
-use_repo(internal_configure, "nanobind")
+use_repo(internal_configure, "nanobind", "pypi__typing_extensions")

internal_configure.bzl

@@ -26,4 +26,12 @@ def _internal_configure_extension_impl(_):
         urls = ["https://github.com/wjakob/nanobind/archive/refs/tags/v%s.tar.gz" % nanobind_version],
     )
 
+    typing_extensions_version = "4.12.2"
+    http_archive(
+        name = "pypi__typing_extensions",
+        build_file = "//:typing_extensions.BUILD",
+        strip_prefix = "typing_extensions-%s" % typing_extensions_version,
+        urls = ["https://files.pythonhosted.org/packages/df/db/f35a00659bc03fec321ba8bce9420de607a1d37f8342eee1863174c69557/typing_extensions-%s.tar.gz" % typing_extensions_version],
+    )
+
 internal_configure_extension = module_extension(implementation = _internal_configure_extension_impl)

nanobind.BUILD

@@ -52,3 +52,5 @@ cc_library(
         "@rules_python//python/cc:current_py_cc_headers",
     ],
 )
+
+exports_files(["src/stubgen.py"])

typing_extensions.BUILD

@@ -0,0 +1,38 @@
+"""
+A version of the Python sdist Bazel template found in
+https://github.com/bazelbuild/rules_python/blob/main/python/private/pypi/deps.bzl ,
+specialized on the ``typing_extensions`` package.
+
+# Copyright 2023 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+
+load("@rules_python//python:defs.bzl", "py_library")
+
+package(default_visibility = ["//visibility:public"])
+
+py_library(
+    name = "lib",
+    srcs = ["src/typing_extensions.py"],
+    data = [
+        "CHANGELOG.md",
+        "LICENSE",
+        "PKG-INFO",
+        "README.md",
+        "pyproject.toml",
+    ],
+    # This makes the source directory a top-level in the Python import
+    # search path for anything that depends on this.
+    imports = ["src"],
+)