taplo: add shell completions

- Version 0.10.0 of Taplo CLI added the ability to generate completions
  for shells (see https://github.com/tamasfe/taplo/releases/tag/0.10.0).

- This commit adds the generated shell completions to the derivation
  output.

- Resolves https://github.com/NixOS/nixpkgs/issues/440875.

pkgs/by-name/ta/taplo/package.nix

@@ -1,10 +1,12 @@
 {
+  stdenv,
   lib,
   rustPlatform,
   fetchCrate,
   pkg-config,
   openssl,
   withLsp ? true,
+  installShellFiles,
 }:
 
 rustPlatform.buildRustPackage rec {
@@ -20,6 +22,7 @@ rustPlatform.buildRustPackage rec {
   cargoHash = "sha256-tvijtB5fwOzQnnK/ClIvTbjCcMeqZpXcRdWWKZPIulM=";
 
   nativeBuildInputs = [
+    installShellFiles
     pkg-config
   ];
 
@@ -29,6 +32,21 @@ rustPlatform.buildRustPackage rec {
 
   buildFeatures = lib.optional withLsp "lsp";
 
+  postInstall =
+    lib.optionalString
+      (
+        stdenv.buildPlatform.canExecute stdenv.hostPlatform
+        &&
+          # Creation of the completions fails on Darwin platforms.
+          !stdenv.hostPlatform.isDarwin
+      )
+      ''
+        installShellCompletion --cmd taplo \
+          --bash <($out/bin/taplo completions bash) \
+          --fish <($out/bin/taplo completions fish) \
+          --zsh <($out/bin/taplo completions zsh)
+      '';
+
   meta = with lib; {
     description = "TOML toolkit written in Rust";
     homepage = "https://taplo.tamasfe.dev";