Add support for formatter specification

compose.go

@@ -123,6 +123,7 @@ type Generator struct {
 	RemoveVolumes           bool
 	NoCreateRootTarget      bool
 	AutoFormat              bool
+	Formatter 				string
 	WriteHeader             bool
 	NoWriteNixSetup         bool
 	DefaultStopTimeout      time.Duration
@@ -210,6 +211,7 @@ func (g *Generator) Run(ctx context.Context) (*NixContainerConfig, error) {
 		Networks:         networks,
 		Volumes:          volumes,
 		CreateRootTarget: !g.NoCreateRootTarget,
+		Formatter:        g.Formatter,
 		AutoStart:        g.AutoStart,
 		WriteNixSetup:    !g.NoWriteNixSetup,
 		AutoFormat:       g.AutoFormat,

flake.nix

@@ -5,9 +5,12 @@
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
     onchg.url = "github:aksiksi/onchg-rs";
     onchg.inputs.nixpkgs.follows = "nixpkgs";
+
+    alejandra.url = "github:kamadorueda/alejandra/3.1.0";
+    alejandra.inputs.nixpkgs.follows = "nixpkgs";
   };
 
-  outputs = { self, nixpkgs, onchg, ... }: let
+  outputs = { self, nixpkgs, onchg, alejandra, ... }: let
     supportedSystems = [ "x86_64-linux" "x86_64-darwin" "aarch64-linux" "aarch64-darwin" ];
     forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
     pkgsFor = system: nixpkgs.legacyPackages.${system};
@@ -17,6 +20,8 @@
     version = "0.3.2-pre";
     # LINT.ThenChange(main.go:version)
   in {
+    # Formatter to be used by helped func
+
     # Nix package
     packages = forAllSystems (system:
       let pkgs = pkgsFor system; in {
@@ -33,7 +38,7 @@
     devShells = forAllSystems (system:
       let pkgs = pkgsFor system; in {
         default = pkgs.mkShell {
-          buildInputs = [ pkgs.go pkgs.gopls pkgs.nixfmt-rfc-style ];
+          buildInputs = [ pkgs.go pkgs.gopls pkgs.nixfmt-rfc-style alejandra.defaultPackage.${system} ];
           # Add a Git pre-commit hook.
           shellHook = onchg.shellHook.${system};
         };

helpers.go

@@ -76,14 +76,15 @@
 
 // formatNixCode will format Nix code by calling 'nixfmt' and passing in the
 // given code via stdin.
-func formatNixCode(contents []byte) ([]byte, error) {
+func formatNixCode(contents []byte, formatter string) ([]byte, error) {
+	//
 	// Check for existence of 'nixfmt' in $PATH.
-	nixfmtPath, err := exec.LookPath("nixfmt")
+	formatterPath, err := exec.LookPath(formatter)
 	if err != nil {
-		return nil, fmt.Errorf("'nixfmt' not found in $PATH: %w", err)
+		return nil, fmt.Errorf("%w not found in $PATH: %w", formatter, err)
 	}
 
-	cmd := exec.Command(nixfmtPath)
+	cmd := exec.Command(formatterPath)
 	cmd.Stdin = bytes.NewBuffer(contents)
 
 	// Overwrite contents with formatted output.

main.go

@@ -40,7 +40,7 @@ var createRootTarget = flag.Bool("create_root_target", true, "if set, a root sys
 var defaultStopTimeout = flag.Duration("default_stop_timeout", defaultSystemdStopTimeout, "default stop timeout for generated container services.")
 var build = flag.Bool("build", false, "if set, generated container build systemd services will be enabled.")
 var writeNixSetup = flag.Bool("write_nix_setup", true, "if true, Nix setup code is written to output (runtime, DNS, autoprune, etc.)")
-var autoFormat = flag.Bool("auto_format", false, `if true, Nix output will be formatted using "nixfmt" (must be present in $PATH).`)
+var formatter = flag.String("formatter", "", `if specified, Nix output will be formatted by formatter specified, supported are nixfmt and alejandra (must be present in $PATH).`)
 var version = flag.Bool("version", false, "display version and exit")
 
 type OsGetWd struct{}
@@ -51,7 +51,7 @@ func (*OsGetWd) GetWd() (string, error) {
 
 func main() {
 	flag.Parse()
-
+	fmt.Println(*formatter)
 	if *version {
 		fmt.Printf("compose2nix v%s\n", appVersion)
 		return
@@ -90,6 +90,9 @@ func main() {
 		}
 		serviceIncludeRegexp = pat
 	}
+	if *formatter != "" && (strings.TrimSpace(*formatter) != "nixfmt" && strings.TrimSpace(*formatter) != "alejandra") {
+		log.Fatal("Invalid formatter provided, needs to be either nixfmt or alejandra")
+	}
 
 	start := time.Now()
 	g := Generator{
@@ -112,7 +115,8 @@ func main() {
 		NoCreateRootTarget:      !*createRootTarget,
 		WriteHeader:             true,
 		NoWriteNixSetup:         !*writeNixSetup,
-		AutoFormat:              *autoFormat,
+		AutoFormat:              *formatter != "",
+		Formatter:               *formatter,
 		DefaultStopTimeout:      *defaultStopTimeout,
 		IncludeBuild:            *build,
 		GetWorkingDir:           &OsGetWd{},

nix.go

@@ -281,6 +281,7 @@ type NixContainerConfig struct {
 	Volumes          []*NixVolume
 	CreateRootTarget bool
 	WriteNixSetup    bool
+	Formatter        string
 	AutoFormat       bool
 	AutoStart        bool
 	IncludeBuild     bool
@@ -310,7 +311,7 @@ func (c *NixContainerConfig) Write(out io.Writer) error {
 	config := []byte(c.String())
 
 	if c.AutoFormat {
-		formatted, err := formatNixCode(config)
+		formatted, err := formatNixCode(config, c.Formatter)
 		if err != nil {
 			return err
 		}