tinymist: generate shell completion (#370033)

pkgs/by-name/ti/tinymist/package.nix

@@ -1,11 +1,14 @@
 {
   lib,
+  stdenv,
   rustPlatform,
   fetchFromGitHub,
+  installShellFiles,
   pkg-config,
   libgit2,
   openssl,
   zlib,
+  buildPackages,
   versionCheckHook,
   nix-update-script,
   vscode-extensions,
@@ -27,7 +30,10 @@ rustPlatform.buildRustPackage rec {
   useFetchCargoVendor = true;
   cargoHash = "sha256-+Ce9qIETGFZXG4RX5GP8tpmH4fkpbPkDS1FX64NQ6/4=";
 
-  nativeBuildInputs = [ pkg-config ];
+  nativeBuildInputs = [
+    installShellFiles
+    pkg-config
+  ];
 
   buildInputs = [
     libgit2
@@ -59,6 +65,17 @@ rustPlatform.buildRustPackage rec {
     "--skip=semantic_tokens_full::tests::test"
   ];
 
+  postInstall =
+    let
+      emulator = stdenv.hostPlatform.emulator buildPackages;
+    in
+    ''
+      installShellCompletion --cmd tinymist \
+        --bash <(${emulator} $out/bin/tinymist completion bash) \
+        --fish <(${emulator} $out/bin/tinymist completion fish) \
+        --zsh <(${emulator} $out/bin/tinymist completion zsh)
+    '';
+
   nativeInstallCheckInputs = [
     versionCheckHook
   ];