Convert the python toolchain example to bzlmod

examples/toolchains/python/.bazeliskrc

@@ -0,0 +1 @@
+USE_BAZEL_VERSION=7.x

examples/toolchains/python/.bazelrc

@@ -1,3 +1,4 @@
 import %workspace%/../../../.bazelrc.remote-cache
 
-build:nix --host_platform=@io_tweag_rules_nixpkgs//nixpkgs/platforms:host
+build:nix --host_platform=@rules_nixpkgs_core//platforms:host
+build:nix --crosstool_top=@nixpkgs_config_cc//:toolchain

examples/toolchains/python/.gitignore

@@ -0,0 +1 @@
+MODULE.bazel.lock

examples/toolchains/python/BUILD

@@ -1,3 +1,5 @@
+load("@rules_python//python:py_binary.bzl", "py_binary")
+
 py_binary(
     name = "hello",
     srcs = ["hello.py"],

examples/toolchains/python/MODULE.bazel

@@ -0,0 +1,54 @@
+module(
+    name = "hello_world_python",
+    version = "0.0.0",
+)
+
+bazel_dep(name = "rules_nixpkgs_core")
+local_path_override(
+    module_name = "rules_nixpkgs_core",
+    path = "../../../core/",
+)
+
+bazel_dep(name = "rules_nixpkgs_cc")
+local_path_override(
+    module_name = "rules_nixpkgs_cc",
+    path = "../../../toolchains/cc",
+)
+
+bazel_dep(name = "rules_nixpkgs_python")
+local_path_override(
+    module_name = "rules_nixpkgs_python",
+    path = "../../../toolchains/python",
+)
+
+bazel_dep(name = "platforms", version = "1.0.0")
+bazel_dep(name = "rules_python", version = "1.7.0")
+bazel_dep(name = "rules_cc", version = "0.2.14")
+
+#
+# Nixpkgs
+#
+
+nix_repo = use_extension("@rules_nixpkgs_core//extensions:repository.bzl", "nix_repo")
+nix_repo.file(
+    name = "nixpkgs",
+    file = "//:nixpkgs.nix",
+    file_deps = [
+        "//:nixpkgs.json",
+    ],
+)
+use_repo(nix_repo, "nixpkgs")
+
+#
+# Toolchains
+#
+
+extension_configure = use_extension("//:extension.bzl", "extension_configure")
+use_repo(extension_configure, "nixpkgs_config_cc")
+use_repo(extension_configure, "nixpkgs_config_cc_toolchains")
+use_repo(extension_configure, "nixpkgs_config_cc_info")
+use_repo(extension_configure, "nixpkgs_python_toolchain")
+use_repo(extension_configure, "nixpkgs_python_toolchain_python3")
+
+register_toolchains("@nixpkgs_config_cc_toolchains//:all")
+register_toolchains("@nixpkgs_python_toolchain//:all")

examples/toolchains/python/README.md

@@ -12,4 +12,4 @@ To run the example with Nix, issue the following command:
 nix-shell --command 'bazel run --config=nix :hello'
 ```
 
-To specify Python version or modules, change the `python3_attribute_path` parameter in the `nixpkgs_python_configure` call in the `WORKSPACE` file.
+To specify Python version or modules, change the `python3_attribute_path` parameter in the `nixpkgs_python_configure` call in the `extension.bzl` file.

examples/toolchains/python/extension.bzl

@@ -0,0 +1,19 @@
+load("@rules_nixpkgs_cc//:cc.bzl", "nixpkgs_cc_configure")
+load("@rules_nixpkgs_python//:python.bzl", "nixpkgs_python_configure")
+
+def _extension_configure_impl(module_ctx):
+    nixpkgs_cc_configure(
+        name = "nixpkgs_config_cc",
+        repository = "@nixpkgs",
+        register = False,
+    )
+
+    nixpkgs_python_configure(
+        python3_attribute_path = "python312.withPackages(ps: with ps; [ numpy opencv4 ])",
+        repository = "@nixpkgs",
+        register = False,
+    )
+
+extension_configure = module_extension(
+    implementation = _extension_configure_impl,
+)

examples/toolchains/python/nixpkgs.json

@@ -1,7 +1,7 @@
 {
   "owner": "NixOS",
   "repo": "nixpkgs",
-  "branch": "nixos-23.11",
-  "rev": "b2cf36f43f9ef2ded5711b30b1f393ac423d8f72",
-  "sha256": "07mmgn752nzh8fish8ff5ar9dbdbiv79qb3hl4sazbckqkw38avc"
+  "branch": "25.05",
+  "rev": "11cb3517b3af6af300dd6c055aeda73c9bf52c48",
+  "sha256": "1915r28xc4znrh2vf4rrjnxldw2imysz819gzhk9qlrkqanmfsxd"
 }

examples/toolchains/python/shell.nix

@@ -1,6 +1,6 @@
 { pkgs ? import ./nixpkgs.nix { } }:
 
 pkgs.mkShellNoCC {
-  nativeBuildInputs = [ pkgs.nix pkgs.bazel_6 ];
+  nativeBuildInputs = [ pkgs.nix pkgs.bazel_7 ];
   env.BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN = "1";
 }