flake.nix

@@ -4,10 +4,9 @@
   # Nixpkgs / NixOS version to use.
   inputs.nixpkgs.url = "nixpkgs/nixos-unstable";
 
-  outputs = {
-    self,
-    nixpkgs,
-  }: let
+  outputs = { self, nixpkgs }:
+    let
+
       # to work with older version of flakes
       lastModifiedDate = self.lastModifiedDate or self.lastModified or "19700101";
 
@@ -15,36 +14,58 @@
       version = builtins.substring 0 8 lastModifiedDate;
 
       # System types to support.
-    supportedSystems = ["x86_64-linux" "aarch64-linux"];
+      supportedSystems = [ "x86_64-linux" "aarch64-linux" ];
 
       # Helper function to generate an attrset '{ x86_64-linux = f "x86_64-linux"; ... }'.
       forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
 
       # Nixpkgs instantiated for supported system types.
-    nixpkgsFor = forAllSystems (system: import nixpkgs {inherit system;});
-  in {
+      nixpkgsFor = forAllSystems (system: import nixpkgs { inherit system; });
+
+    in
+    {
+
       # Provide some binary packages for selected system types.
-    packages = forAllSystems (system: let
+      packages = forAllSystems (system:
+        let
           pkgs = nixpkgsFor.${system};
-    in {
+        in
+        {
           swaysw = pkgs.buildGoModule {
             pname = "swaysw";
             inherit version;
+            # In 'nix develop', we don't need a copy of the source tree
+            # in the Nix store.
             src = ./.;
-        ldFlags = ["-s -w"];
+
+            # This hash locks the dependencies of this package. It is
+            # necessary because of how Go requires network access to resolve
+            # VCS.  See https://www.tweag.io/blog/2021-03-04-gomod2nix/ for
+            # details. Normally one can build with a fake sha256 and rely on native Go
+            # mechanisms to tell you what the hash should be or determine what
+            # it should be "out-of-band" with other tooling (eg. gomod2nix).
+            # To begin with it is recommended to set this, but one must
+            # remeber to bump this hash when your dependencies change.
             vendorSha256 = null;
 
+            #vendorSha256 = "sha256-pQpattmS9VmO3ZIQUFn66az8GSmB4IvYhTTCFn6SUmo=";
           };
         });
       
-    devShells = forAllSystems (system: let
+      # Add dependencies that are only needed for development
+      devShells = forAllSystems (system:
+        let 
           pkgs = nixpkgsFor.${system};
-    in {
+        in
+        {
           default = pkgs.mkShell {
-        buildInputs = with pkgs; [go gopls gotools go-tools wofi];
+            buildInputs = with pkgs; [ go gopls gotools go-tools wofi ];
           };
         });
 
+      # The default package for 'nix build'. This makes sense if the
+      # flake provides only one package or there is a clear "main"
+      # package.
       defaultPackage = forAllSystems (system: self.packages.${system}.swaysw);
     };
 }

main.go

@@ -44,7 +44,7 @@ func selectWithWofi(windows string) string {
 	cmd.Stdin = strings.NewReader(windows)
 	stdout, err := cmd.Output()
 	if err != nil {
-		return ""
+		log.Fatal(err)
 	}
 	return strings.TrimSpace(string(stdout))
 }
@@ -82,8 +82,7 @@ func main() {
 	var windows []window
 	flatten(swaymsg_output, &windows)
 
-	if selected := selectWithWofi(getWindowNames(windows)); selected != "" {
+	selected := selectWithWofi(getWindowNames(windows))
 	windowId := findWindowId(selected, windows)
 	switchToWindow(windowId)
-	}
 }