feat: remove snowfall and use flake-parts (#12)

- Snowfall lib is a bit opinionated and its better to rely on something less intrusive.
- We now use `flake-parts` where we load all `.parts.nix` modules with `import-tree`.
- Toolchain files can be placed in the folder `./tools/nix/toolchains` which then can be used to define 
  `devShells` in `./tools/nix/shells` . Each `toolchain-*.nix` file returns an attrset of devenv modules (can 
  be functions or pure attrsets, currently only attrsets are used).
- The `perSystem` flake-parts config receives two additional parameters `pkgs` and `pkgsStable` which
  are the imported `nixpkgs` and `nixpkgs-stable` inputs.
- `just/nix.just` is introduced to outsource some stuff.
- python env in `setup` only calls `uv sync` which is better, respecting the set 
  variables `UV_PROJECT_ENVIRONMENT` etc.

Author: gabyx

.github/actions/setup-nix/action.yaml

@@ -12,10 +12,10 @@ inputs:
 runs:
   using: "composite"
   steps:
-    - uses: cachix/install-nix-action@v30
+    - uses: cachix/install-nix-action@v31
       with:
         nix_path: nixpkgs=channel:nixos-unstable
-    - uses: cachix/cachix-action@v15
+    - uses: cachix/cachix-action@v16
       with:
         name: "${{ inputs.cachix_cache_name }}"
         authToken: "${{ inputs.cachix_auth_token }}"

justfile

@@ -6,6 +6,7 @@ output_dir := root_dir / ".output"
 flake_dir := root_dir / "./tools/nix"
 
 mod maintenance "./tools/just/maintenance.just"
+mod nix "./tools/just/nix.just"
 
 # Default target if you do not specify a target.
 default:
@@ -38,20 +39,8 @@ nix-list *args:
 
 # Enter the default Nix development shell.
 develop *args:
-    just nix-develop default "$@"
+    just nix::develop default "$@"
 
 # Enter the CI Nix development shell.
 ci *args:
-    just nix-develop ci "$@"
-
-# Enter the Nix development shell `$1` and execute the command `${@:2}`.
-[private]
-nix-develop *args:
-    #!/usr/bin/env bash
-    set -eu
-    cd "{{root_dir}}"
-    shell="$1"; shift 1;
-    args=("$@") && [ "${#args[@]}" != 0 ] || args="$SHELL"
-    nix develop --no-pure-eval --accept-flake-config \
-        "{{flake_dir}}#$shell" \
-        --command "${args[@]}"
+    just nix::develop ci "$@"

src/.jinja/common/justfile

@@ -6,13 +6,15 @@ flake_dir := root_dir / "tools/nix"
 output_dir := root_dir / ".output"
 build_dir := output_dir / "build"
 
+mod nix "./tools/just/nix.just"
+
 # Default target if you do not specify a target.
 default:
     just --list --unsorted
 
 # Enter the default Nix development shell and execute the command `"$@`.
 develop *args:
-    just nix-develop "default" "$@"
+    just nix::develop "default" "$@"
 
 # Format the project.
 format *args:
@@ -25,22 +27,10 @@ setup *args:
 
 # Run commands over the ci development shell.
 ci *args:
-    just nix-develop "ci" "$@"
+    just nix::develop "ci" "$@"
 
 ## Nix Stuff ==================================================================
 # Show all packages configured in the Nix `flake.nix`.
 nix-list *args:
     cd tools/nix && nix flake --no-pure-eval show
-
-# Enter the Nix `devShell` with name `$1` and execute the command `${@:2}` (default command is '$SHELL')
-[private]
-nix-develop *args:
-    #!/usr/bin/env bash
-    set -eu
-    cd "{{root_dir}}"
-    shell="$1"; shift 1;
-    args=("$@") && [ "${#args[@]}" != 0 ] || args="$SHELL"
-    nix develop --no-pure-eval --accept-flake-config \
-        "{{flake_dir}}#$shell" --command "${args[@]}"
-## ============================================================================
 {%- endraw -%}

src/generic/tools/ci/general.sh

@@ -67,13 +67,13 @@ function ci::setup_python_venv() {
     root_dir=$(git rev-parse --show-toplevel)
 
     # If VIRTUAL_ENV is set use it.
-    local venv_dir="${VIRTUAL_ENV:-$root_dir/.venv}"
-    ci::print_info "Python virtual env. dir '$venv_dir' set."
-    if [ ! -d "$venv_dir" ]; then
-        ci::print_info "Setting up venv environment in '$venv_dir'."
-        uv venv "$venv_dir" &>/dev/null
-    fi
+    export VIRTUAL_ENV="${VIRTUAL_ENV:-$root_dir/.venv}"
+    export UV_PROJECT_ENVIRONMENT="$VIRTUAL_ENV"
+
+    ci::print_info "Python virtual env. dir '$UV_PROJECT_ENVIRONMENT' set."
 
-    ci::print_info "Installing pip dependencies..."
-    uv pip install -r "$root_dir/pyproject.toml" &>/dev/null
+    if [ ! -d "$UV_PROJECT_ENVIRONMENT" ]; then
+        ci::print_info "Setting up venv environment in '$UV_PROJECT_ENVIRONMENT'."
+        uv sync
+    fi
 }

src/generic/tools/just/nix.just

@@ -0,0 +1,72 @@
+set positional-arguments
+set shell := ["bash", "-cue"]
+
+default:
+    just --list --unsorted -f "{{source_file()}}"
+
+# Enter the Nix development shell `$1` and execute the command `${@:2}`.
+[no-cd]
+develop *args:
+    #!/usr/bin/env bash
+    set -eu
+    root_dir=$(git rev-parse --show-toplevel) || exit 1
+    flake_dir="$root_dir/tools/nix"
+
+    shell="$1"; shift 1;
+    args=("$@") && [ "${#args[@]}" != 0 ] ||
+        args=(env SHELL="$SHELL" "$SHELL")
+
+    nix_args=("--no-pure-eval")
+
+    nix develop \
+        "${nix_args[@]}" \
+        --accept-flake-config \
+        "$flake_dir#$shell" \
+        --command "${args[@]}"
+
+# Start an Nix interpreter with loaded flake.
+[no-cd]
+repl *args:
+    #!/usr/bin/env bash
+    set -eu
+
+    root_dir=$(git rev-parse --show-toplevel) || exit 1
+    flake_dir="$root_dir/tools/nix"
+    nix_args=("--no-pure-eval" "$@")
+
+    nix repl \
+        "${nix_args[@]}" \
+        --accept-flake-config \
+        "$flake_dir"
+
+# Build a package in the `packages` output of `flake.nix`
+alias build := package
+[no-cd]
+package attrname *args:
+    #!/usr/bin/env bash
+    set -eu
+    root_dir=$(git rev-parse --show-toplevel) || exit 1
+    flake_dir="$root_dir/tools/nix"
+    nix_args=("${@:2}")
+
+    mkdir -p .output/package
+    outlink=".output/package/{{attrname}}"
+    nix build \
+        --accept-flake-config \
+        "${nix_args[@]}" \
+        -L "$flake_dir#{{attrname}}" \
+        --out-link "$outlink" --json
+
+# Show all packages.
+[no-cd]
+package-show:
+    #!/usr/bin/env bash
+    set -eu
+    root_dir=$(git rev-parse --show-toplevel) || exit 1
+    flake_dir="$root_dir/tools/nix"
+
+    # We cannot use `nix flake show` due to other systems where
+    # IFD (import-from-derivation -> from-yaml Nix derivation)
+    # does not work.
+    system=$(nix eval --impure --raw --expr builtins.currentSystem)
+    nix eval --json "$flake_dir#packages.$system" | jq