docker-language-server: install shell completion

pkgs/by-name/do/docker-language-server/package.nix

@@ -1,10 +1,12 @@
 {
+  stdenv,
   lib,
   fetchFromGitHub,
   buildGoModule,
   docker,
   gotestsum,
   versionCheckHook,
+  installShellFiles,
 }:
 
 buildGoModule (finalAttrs: {
@@ -20,6 +22,10 @@ buildGoModule (finalAttrs: {
 
   vendorHash = "sha256-ztA+/4l180UKTKrsqTyysDcD4oQSDgnBYUaiKDF6LvI=";
 
+  nativeBuildInputs = [
+    installShellFiles
+  ];
+
   nativeCheckInputs = [
     docker
     gotestsum
@@ -53,6 +59,13 @@ buildGoModule (finalAttrs: {
   ];
   doInstallCheck = true;
 
+  postInstall = lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''
+    installShellCompletion --cmd '${finalAttrs.meta.mainProgram}' \
+      --bash <("$out/bin/${finalAttrs.meta.mainProgram}" completion bash) \
+      --zsh <("$out/bin/${finalAttrs.meta.mainProgram}" completion zsh) \
+      --fish <("$out/bin/${finalAttrs.meta.mainProgram}" completion fish)
+  '';
+
   meta = {
     description = "Language server for providing language features for file types in the Docker ecosystem (Dockerfiles, Compose files, and Bake files)";
     homepage = "https://github.com/docker/docker-language-server";