build: add Bazel Rust workflow

.gitignore

@@ -17,6 +17,9 @@ Thumbs.db
 # logs
 *.log
 
+# Bazel convenience symlinks
+/bazel-*
+
 # language package-manager caches and outputs
 node_modules/
 dist/

AGENTS.md

@@ -34,3 +34,6 @@
 
 - When materializing an external specification, standard, or project-maintained convention, use the upstream source instead of reconstructing it from memory.
   Preserve local policy separately from copied upstream text.
+- After an explicit squash or rewrite request on a pull request, subsequent pull-request updates still use follow-up commits unless the user explicitly asks for another rewrite.
+- Starlark top-level rule and extension declarations cannot reference implementation functions before those functions are assigned.
+  Keep executable public interface declarations after their implementation symbols, or validate before committing a top-down rewrite.

MODULE.bazel

@@ -0,0 +1,8 @@
+module(name = "alexion", version = "0.1.0")
+
+bazel_dep(name = "rules_rust", version = "0.74.0")
+
+rust = use_extension("//bazel:rust.bzl", "rust")
+use_repo(rust, "rust")
+
+register_toolchains("@rust//:rust")

bazel/BUILD

@@ -0,0 +1,5 @@
+exports_files([
+    "rust.BUILD.template",
+    "rust.bzl",
+    "utils.bzl",
+])

bazel/rust.BUILD.template

@@ -0,0 +1,117 @@
+filegroup(
+    name = "rustc",
+    srcs = ["toolchain/bin/rustc"],
+    visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "rustdoc",
+    srcs = ["toolchain/bin/rustdoc"],
+    visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "cargo",
+    srcs = ["toolchain/bin/cargo"],
+    visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "cargo_clippy",
+    srcs = ["toolchain/bin/cargo-clippy"],
+    visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "clippy_driver",
+    srcs = ["toolchain/bin/clippy-driver"],
+    visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "rustfmt",
+    srcs = ["toolchain/bin/rustfmt"],
+    visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "cc",
+    srcs = ["toolchain/bin/cc"],
+    visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "rustc_lib",
+    srcs = glob(
+        [
+            "rust/lib/*.so*",
+            "rust/lib/rustlib/{host_triple}/codegen-backends/*.so",
+            "rust/lib/rustlib/{host_triple}/lib/*.so*",
+            "rust/lib/rustlib/{host_triple}/lib/*.rmeta",
+        ],
+        allow_empty = True,
+    ),
+    visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "rust_objcopy",
+    srcs = glob(
+        ["rust/lib/rustlib/{host_triple}/bin/rust-objcopy"],
+        allow_empty = True,
+    ),
+    visibility = ["//visibility:public"],
+)
+
+load("@rules_rust//rust:toolchain.bzl", "rust_stdlib_filegroup")
+
+rust_stdlib_filegroup(
+    name = "rust_std",
+    srcs = glob(
+        [
+            "rust/lib/rustlib/{host_triple}/lib/*.rlib",
+            "rust/lib/rustlib/{host_triple}/lib/*.rmeta",
+            "rust/lib/rustlib/{host_triple}/lib/*.so*",
+            "rust/lib/rustlib/{host_triple}/lib/*.a",
+            "rust/lib/rustlib/{host_triple}/lib/self-contained/**",
+        ],
+        allow_empty = True,
+    ),
+    visibility = ["//visibility:public"],
+)
+
+load("@rules_rust//rust:toolchain.bzl", "rust_toolchain")
+
+rust_toolchain(
+    name = "toolchain_impl",
+    rust_doc = ":rustdoc",
+    rust_std = ":rust_std",
+    rustc = ":rustc",
+    linker = ":cc",
+    linker_type = "indirect",
+    rust_objcopy = ":rust_objcopy",
+    rustfmt = ":rustfmt",
+    cargo = ":cargo",
+    clippy_driver = ":clippy_driver",
+    cargo_clippy = ":cargo_clippy",
+    rustc_lib = ":rustc_lib",
+    allocator_library = None,
+    global_allocator_library = None,
+    binary_ext = "",
+    staticlib_ext = ".a",
+    dylib_ext = ".so",
+    stdlib_linkflags = ["-ldl", "-lpthread"],
+    default_edition = "2024",
+    exec_triple = "{host_triple}",
+    target_triple = "{host_triple}",
+    version = "{release}",
+    channel = "stable",
+    visibility = ["//visibility:public"],
+)
+
+toolchain(
+    name = "rust",
+    toolchain = ":toolchain_impl",
+    toolchain_type = "@rules_rust//rust:toolchain_type",
+    visibility = ["//visibility:public"],
+)

bazel/rust.bzl

@@ -0,0 +1,51 @@
+load("//bazel:utils.bzl", "execute", "require_env")
+
+
+def _rust_repository_impl(repository_ctx):
+    root = repository_ctx.path(require_env(repository_ctx, "RUST_TOOLCHAIN_ROOT"))
+    rustc = root.get_child("bin/rustc")
+
+    sysroot = execute(repository_ctx, [str(rustc), "--print", "sysroot"])
+    verbose_version = execute(repository_ctx, [str(rustc), "-vV"])
+
+    host_triple = None
+    release = None
+    for line in verbose_version.splitlines():
+        if line.startswith("host: "):
+            host_triple = line.removeprefix("host: ")
+        if line.startswith("release: "):
+            release = line.removeprefix("release: ")
+
+    if host_triple == None:
+        fail("rustc -vV did not report a host triple")
+    if release == None:
+        fail("rustc -vV did not report a release")
+
+    repository_ctx.symlink(root, "toolchain")
+    repository_ctx.symlink(sysroot, "rust")
+
+    repository_ctx.file("WORKSPACE.bazel", "")
+    repository_ctx.template(
+        "BUILD.bazel",
+        Label("//bazel:rust.BUILD.template"),
+        {
+            "{host_triple}": host_triple,
+            "{release}": release,
+        },
+    )
+
+
+rust_repository = repository_rule(
+    implementation = _rust_repository_impl,
+    local = True,
+    environ = ["RUST_TOOLCHAIN_ROOT"],
+)
+
+
+def _rust_impl(module_ctx):
+    rust_repository(name = "rust")
+
+
+rust = module_extension(
+    implementation = _rust_impl,
+)

bazel/utils.bzl

@@ -0,0 +1,12 @@
+def require_env(repository_ctx, variable):
+    value = repository_ctx.os.environ.get(variable)
+    if not value:
+        fail("{} must be set.".format(variable))
+    return value
+
+
+def execute(repository_ctx, arguments):
+    result = repository_ctx.execute(arguments)
+    if result.return_code != 0:
+        fail("command failed: {}\n{}".format(" ".join(arguments), result.stderr))
+    return result.stdout.strip()

configs/nixos/hosts/neogaia/default.nix

@@ -40,6 +40,7 @@
   modules.network.ssh.hostKeys.sopsFile = ../../secrets/neogaia.yaml;
   modules.network.ssh.userKey.sopsFile = ../../secrets/neogaia.yaml;
 
+  modules.monorepo.enable = true;
   modules.shell.herdr.enable = true;
   modules.agents.tools.gitea-axi.enable = true;
   modules.agents.pi.enable = true;

configs/nixos/modules/default.nix

@@ -120,7 +120,6 @@ in
     modules.shell.tmux.enable = lib.mkDefault true;
     modules.shell.nvim.enable = lib.mkDefault true;
     modules.shell.git.enable = lib.mkDefault true;
-    modules.shell.direnv.enable = lib.mkDefault true;
     modules.shell.yazi.enable = lib.mkDefault true;
   };
 }

configs/nixos/modules/monorepo.nix

@@ -0,0 +1,17 @@
+{
+  config,
+  lib,
+  ...
+}:
+# Tools for developing this monorepo.
+let
+  cfg = config.modules.monorepo;
+in
+{
+  options.modules.monorepo.enable = lib.mkEnableOption "tools for developing this monorepo";
+
+  config = lib.mkIf cfg.enable {
+    modules.shell.bazel.enable = true;
+    modules.shell.rust.enable = true;
+  };
+}

configs/nixos/modules/shell/bazel.nix

@@ -0,0 +1,18 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+# Bazel for the primary user's shell environment.
+let
+  cfg = config.modules.shell.bazel;
+  user = config.user.name;
+in
+{
+  options.modules.shell.bazel.enable = lib.mkEnableOption "Bazel for the primary user's shell environment";
+
+  config = lib.mkIf cfg.enable {
+    home-manager.users.${user}.home.packages = [ pkgs.bazel ];
+  };
+}

configs/nixos/modules/shell/rust.nix

@@ -0,0 +1,35 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+# Rust tools for the primary user's shell environment.
+let
+  cfg = config.modules.shell.rust;
+  user = config.user.name;
+  toolchain = pkgs.symlinkJoin {
+    name = "rust-toolchain";
+    paths = with pkgs; [
+      cargo
+      clippy
+      gcc
+      rustc
+      rustfmt
+    ];
+  };
+in
+{
+  options.modules.shell.rust.enable = lib.mkEnableOption "Rust tools for the primary user's shell environment";
+
+  config = lib.mkIf cfg.enable {
+    home-manager.users.${user} = {
+      home.packages = [
+        toolchain
+        pkgs.rust-analyzer
+      ];
+
+      home.sessionVariables.RUST_TOOLCHAIN_ROOT = "${toolchain}";
+    };
+  };
+}

flake.nix

@@ -55,12 +55,14 @@
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
+    # TODO: deprecate / remove
     # Agent-ergonomic CLI for Gitea, with a home-manager module for the agent context.
     gitea-axi = {
       url = "git+https://git.alexion.dev/alexion/gitea-axi";
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
+    # TODO: deprecate / remove
     # Personal agent skills, packaged as per-skill derivations with a home-manager module.
     skills = {
       url = "git+https://git.alexion.dev/alexion/skills";

src/machoke/BUILD

@@ -0,0 +1,13 @@
+load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_library")
+
+rust_library(
+    name = "machoke_lib",
+    crate_name = "machoke",
+    srcs = ["lib.rs"],
+)
+
+rust_binary(
+    name = "machoke",
+    srcs = ["main.rs"],
+    deps = [":machoke_lib"],
+)

src/machoke/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "machoke"
+version = "0.1.0"

src/machoke/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "machoke"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+path = "lib.rs"
+
+[[bin]]
+name = "machoke"
+path = "main.rs"
+
+[dependencies]

src/machoke/lib.rs

@@ -0,0 +1,3 @@
+pub fn greeting() -> &'static str {
+    "Hello from machoke"
+}

src/machoke/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("{}", machoke::greeting());
+}