notation: provide completions when cross-compiling

{

  lib,

  stdenv,

  buildGoModule,

  fetchFromGitHub,

  installShellFiles,

  testers,

  stdenv,

  buildPackages,

}:

buildGoModule (finalAttrs: {

    "-X github.com/notaryproject/notation/internal/version.BuildMetadata="

  ];

  postInstall = lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''

    installShellCompletion --cmd notation \

      --bash <($out/bin/notation completion bash) \

      --fish <($out/bin/notation completion fish) \

      --zsh <($out/bin/notation completion zsh)

  postInstall =

    let

      exe =

        if stdenv.buildPlatform.canExecute stdenv.hostPlatform then

          "${placeholder "out"}/bin/${finalAttrs.meta.mainProgram}"

        else

          lib.getExe buildPackages.notation;

    in

    ''

      installShellCompletion --cmd ${finalAttrs.meta.mainProgram} \

        --bash <(${exe} completion bash) \

        --fish <(${exe} completion fish) \

        --zsh <(${exe} completion zsh)

    '';

  passthru.tests.version = testers.testVersion {