add shell completion

nix/default.nix

@@ -4,8 +4,10 @@
 , cargoToml
 , cargoLock
 , src
+, installShellFiles
 }:
 let
+  mainProgram = (lib.head cargoToml.bin).name;
 in
 rustPlatform.buildRustPackage {
   pname = cargoToml.package.name;
@@ -14,9 +16,20 @@ rustPlatform.buildRustPackage {
 
   cargoLock.lockFile = cargoLock;
 
+  nativeBuildInputs = [ installShellFiles ];
+  postInstall = let
+    commands = lib.mapCartesianProduct ({ shell, command }: ''
+      "$out/bin/${mainProgram}" generate-completions --shell "${shell}" --command "${command}" > "$TMP/mysqladm.${shell}"
+      installShellCompletion "--${shell}" --cmd "${command}" "$TMP/mysqladm.${shell}"
+    '') {
+      shell = [ "bash" "zsh" "fish" ];
+      command = [ "mysqladm" "mysql-dbadm" "mysql-useradm" ];
+    };
+  in lib.concatStringsSep "\n" commands;
+
   meta = with lib; {
     license = licenses.mit;
     platforms = platforms.linux ++ platforms.darwin;
-    mainProgram = (lib.head cargoToml.bin).name;
+    inherit mainProgram;
   };
 }