Add free-threading support (#39)

* Add support for free-threaded Python

Contains a flag for setting `NB_FREE_THREADED`, and config settings for
each.

* Bump pre-commit buildifier

Via `pre-commit autoupdate`.

* Try again with pinned setuptools in nanobind_example CI

* Add integrity hash to nanobind v2.2.0

.pre-commit-config.yaml

@@ -1,6 +1,6 @@
 repos:
   -   repo: https://github.com/keith/pre-commit-buildifier
-      rev: 6.4.0
+      rev: 7.3.1
       hooks:
       -   id: buildifier
       -   id: buildifier-lint

BUILD

@@ -24,6 +24,21 @@ config_setting(
     flag_values = {":minsize": "False"},
 )
 
+bool_flag(
+    name = "free_threading",
+    build_setting_default = False,
+)
+
+config_setting(
+    name = "with_free_threading",
+    flag_values = {":free_threading": "True"},
+)
+
+config_setting(
+    name = "without_free_threading",
+    flag_values = {":free_threading": "False"},
+)
+
 string_flag(
     name = "py-limited-api",
     build_setting_default = "unset",

MODULE.bazel

@@ -5,9 +5,9 @@ module(
 )
 
 bazel_dep(name = "platforms", version = "0.0.10")
-bazel_dep(name = "rules_cc", version = "0.0.9")
-bazel_dep(name = "rules_python", version = "0.32.2")
-bazel_dep(name = "bazel_skylib", version = "1.6.1")
+bazel_dep(name = "rules_cc", version = "0.0.10")
+bazel_dep(name = "rules_python", version = "0.36.0")
+bazel_dep(name = "bazel_skylib", version = "1.7.1")
 
 # Creates a `http_archive` for nanobind and robin-map.
 internal_configure = use_extension("//:internal_configure.bzl", "internal_configure_extension")

helpers.bzl

@@ -54,3 +54,10 @@ def extension_name(name):
         "@nanobind_bazel//:stable-abi-unix": name + ".abi3.so",
         "@nanobind_bazel//:unstable-abi-unix": name + ".so",
     })
+
+# Optionally add a define for free-threaded nanobind builds.
+def nb_free_threading():
+    return select({
+        "@nanobind_bazel//:with_free_threading": ["NB_FREE_THREADED"],
+        "@nanobind_bazel//:without_free_threading": [],
+    })

internal_configure.bzl

@@ -17,12 +17,12 @@ def _internal_configure_extension_impl(_):
         urls = ["https://github.com/Tessil/robin-map/archive/refs/tags/v%s.tar.gz" % robin_map_version],
     )
 
-    nanobind_version = "2.0.0"
+    nanobind_version = "2.2.0"
     http_archive(
         name = "nanobind",
         build_file = "//:nanobind.BUILD",
         strip_prefix = "nanobind-%s" % nanobind_version,
-        integrity = "sha256-LnBydITtt6hkXSb2qfZzUqZoZXw03npgO/nGjly/j/k=",
+        integrity = "sha256-v7/H5XWfFmnk3bSHUrHdxWR9FDDpRhTW+GJt8dUI5lo=",
         urls = ["https://github.com/wjakob/nanobind/archive/refs/tags/v%s.tar.gz" % nanobind_version],
     )
 

nanobind.BUILD

@@ -9,6 +9,7 @@ load(
     "@nanobind_bazel//:helpers.bzl",
     "maybe_compact_asserts",
     "nb_common_opts",
+    "nb_free_threading",
     "nb_sizeopts",
     "nb_stripopts",
     "py_limited_api",
@@ -29,7 +30,7 @@ cc_library(
         "//conditions:default": [],
     }),
     copts = nb_common_opts(mode = "library") + nb_sizeopts(),
-    defines = py_limited_api(),
+    defines = py_limited_api() + nb_free_threading(),
     includes = ["include"],
     linkopts = select({
         "@platforms//os:linux": ["-Wl,--gc-sections"],