vrc-get: Install shell completions

vrc-get: Generate completions when cross-compiling

pkgs/tools/misc/vrc-get/default.nix

@@ -1,4 +1,4 @@
-{ fetchCrate, lib, rustPlatform, pkg-config, stdenv, Security, SystemConfiguration }:
+{ fetchCrate, installShellFiles, lib, rustPlatform, pkg-config, stdenv, Security, SystemConfiguration, buildPackages }:
 
 rustPlatform.buildRustPackage rec {
   pname = "vrc-get";
@@ -9,12 +9,25 @@ rustPlatform.buildRustPackage rec {
     hash = "sha256-+xbHw1DpFmapjsFoUvxUqTok8TKMebMw3gYjO/rx/iU=";
   };
 
-  nativeBuildInputs = [ pkg-config ];
+  nativeBuildInputs = [ installShellFiles pkg-config ];
 
   buildInputs = lib.optionals stdenv.isDarwin [ Security SystemConfiguration ];
 
   cargoHash = "sha256-iuLhDcii+wXDNUsUMo8lj4kfJve5RAz7FT5Pxs9yFPQ=";
 
+  # Execute the resulting binary to generate shell completions, using emulation if necessary when cross-compiling.
+  # If no emulator is available, then give up on generating shell completions
+  postInstall =
+    let
+      vrc-get = "${stdenv.hostPlatform.emulator buildPackages} $out/bin/vrc-get";
+    in
+    lib.optionalString (stdenv.hostPlatform.emulatorAvailable buildPackages) ''
+      installShellCompletion --cmd vrc-get \
+        --bash <(${vrc-get} completion bash) \
+        --fish <(${vrc-get} completion fish) \
+        --zsh <(${vrc-get} completion zsh)
+    '';
+
   meta = with lib; {
     description = "Command line client of VRChat Package Manager, the main feature of VRChat Creator Companion (VCC)";
     homepage = "https://github.com/vrc-get/vrc-get";