Add formatter targets and pre-commit hooks

.agents/codebase-insights.txt

@@ -0,0 +1 @@
+flake.nix defines a pre-commit check using git-hooks.nix. Run 'nix develop' to install git hooks.

.agents/codex-setup

@@ -10,6 +10,8 @@ sudo apt-get install -y --no-install-recommends \
   libclang-dev \
   capnproto libcapnp-dev
 
+rustup component add rustfmt
+
 pushd ..
   just build-extension
 popd

.agents/tasks/2025/06/29-1712-add-format-and-precommit

@@ -0,0 +1 @@
+Add just targets for running auto formatters (e.g just format). Setup a git pre commit that checks that lints pass using the same technique employed by the Blocksense-network blocksense repo

.agents/tasks/2025/06/29-1757-format-lint-subcommands

@@ -0,0 +1 @@
+Break format and lint tasks into per-language subcommands

.gitignore

@@ -7,6 +7,9 @@ reports/
 test/benchmarks/tmp/
 .direnv/
 .idea/
+
+# Generated by git-hooks.nix
+.pre-commit-config.yaml
 pkg/
 
 # Built ruby gems

Justfile

@@ -8,3 +8,33 @@ bench pattern="*" write_report="console":
 
 build-extension:
     cargo build --release --manifest-path gems/codetracer-ruby-recorder/ext/native_tracer/Cargo.toml
+
+format-rust:
+    cargo fmt --manifest-path gems/codetracer-ruby-recorder/ext/native_tracer/Cargo.toml
+
+format-nix:
+    if command -v nixfmt >/dev/null; then find . -name '*.nix' -print0 | xargs -0 nixfmt; fi
+
+format-ruby:
+    if command -v bundle >/dev/null && bundle exec rubocop -v >/dev/null 2>&1; then bundle exec rubocop -A; else echo "Ruby formatter not available; skipping"; fi
+
+format:
+    just format-rust
+    just format-ruby
+    just format-nix
+
+lint-rust:
+    cargo fmt --check --manifest-path gems/codetracer-ruby-recorder/ext/native_tracer/Cargo.toml
+
+lint-nix:
+    if command -v nixfmt >/dev/null; then find . -name '*.nix' -print0 | xargs -0 nixfmt --check; fi
+
+lint-ruby:
+    find . -name '*.rb' -print0 | xargs -0 -n 1 ruby -wc
+
+lint:
+    just lint-rust
+    just lint-ruby
+    just lint-nix
+
+alias fmt := format

README.md

@@ -129,6 +129,25 @@ We'd be very happy if the community finds this useful, and if anyone wants to:
 
 For maintainer instructions, see [MAINTAINERS.md](MAINTAINERS.md).
 
+### Development workflow
+
+Use [just](https://github.com/casey/just) for common tasks:
+
+```bash
+just build-extension  # compile native extension
+just test             # run the test suite
+just format           # apply automatic formatting for all languages
+just lint             # run all linters
+
+# Language-specific tasks
+just format-rust      # Rust code
+just format-ruby      # Ruby code (requires rubocop)
+just format-nix       # Nix files
+just lint-rust        # Rust formatting check
+just lint-ruby        # Ruby syntax check
+just lint-nix         # Nix formatting check
+```
+
 ### Legal info
 
 LICENSE: MIT

flake.nix

@@ -2,16 +2,34 @@
   description = "Development environment for codetracer-ruby-recorder";
 
   inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
+  inputs.pre-commit-hooks.url = "github:cachix/git-hooks.nix";
 
   outputs = {
     self,
     nixpkgs,
+    pre-commit-hooks,
   }: let
     systems = ["x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin"];
     forEachSystem = nixpkgs.lib.genAttrs systems;
   in {
+    checks = forEachSystem (system: {
+      pre-commit-check = pre-commit-hooks.lib.${system}.run {
+        src = ./.;
+        hooks = {
+          lint = {
+            enable = true;
+            name = "Lint";
+            entry = "just lint";
+            language = "system";
+            pass_filenames = false;
+          };
+        };
+      };
+    });
+
     devShells = forEachSystem (system: let
-      pkgs = import nixpkgs {inherit system;};
+      pkgs = import nixpkgs { inherit system; };
+      preCommit = self.checks.${system}.pre-commit-check;
       isLinux = pkgs.stdenv.isLinux;
       isDarwin = pkgs.stdenv.isDarwin;
     in {
@@ -43,7 +61,7 @@
           # Required for Ruby C extension compilation on macOS
           darwin.apple_sdk.frameworks.CoreFoundation
           darwin.apple_sdk.frameworks.Security
-        ];
+        ] ++ preCommit.enabledPackages;
 
         # Environment variables required to fix build issues with rb-sys/bindgen
 
@@ -56,6 +74,8 @@
         CLANG_PATH = "${pkgs.llvmPackages.clang}/bin/clang";
         CC = "${pkgs.llvmPackages.clang}/bin/clang";
         CXX = "${pkgs.llvmPackages.clang}/bin/clang++";
+
+        inherit (preCommit) shellHook;
       } // pkgs.lib.optionalAttrs isLinux {
         # BINDGEN_EXTRA_CLANG_ARGS: Additional clang arguments for bindgen when parsing Ruby headers
         # Includes system header paths that are not automatically discovered in NixOS