# Typing a plugin

Type the plugins you attached on this.core with seedcord codegen. Covers what the generated Core block holds and when to run codegen again.

You attached the plugin, but `this.core.db` still fails to compile. The property is there when the bot runs, so only the types are missing. `attach` returns a bot typed with `db`, but a handler reads `this.core`. seedcord declares the type of `this.core` in its own package, which never imports your bot file.

A `declare module` block written by hand for every key works too, though you'd have to update it each time you rename one. `seedcord codegen` writes that block for you into `src/seedcord-gen.d.ts`.

```ts title="src/handlers/History.ts"
@SlashRoute('history')
export class History extends SlashHandler<'history'> {
    public async execute(): Promise<void> {
        await this.reply(String(this.core.db));
    }
}
```

TypeScript reports "Property 'db' does not exist on type 'Core'" on `this.core.db`. Nothing is wrong with the handler itself.

## What codegen writes

Every key you attached becomes one row on `Core`, sorted by key. The same file also holds your command and emoji registries, which this sample leaves out.

```ts title="src/seedcord-gen.d.ts" output
// Generated by `seedcord codegen`. Do not edit by hand.
// Run `seedcord codegen` after changing your commands, plugins, or emoji config.

import type Bot from './bot';

// prettier-ignore
declare module '@seedcord/gateway' {
    interface Core {
        db: (typeof Bot)['db'];
    }
    // SlashRegistry, the context menu registries, and EmojiMap follow
}

export {};
```

`Bot` is the default export of the file your `instance` config key points at. Each row reads its type straight from that bot, so `db` gets exactly the type `attach` produced, `Mongoose` here. If you export the bot only as a named const, codegen stops with the code `CliInstanceInvalid` before it writes anything.

The [`Core`](https://docs.seedcord.org/packages/gateway/latest/core) block only appears once you've attached something.

> **Gateway and http differ**
>
> Each transport package declares its own `Core`, so the `declare module` line uses the package you import `Seedcord` from. A gateway bot's file starts with `declare module '@seedcord/gateway'`, and an http bot's starts with `declare module '@seedcord/http'`.

## When to run it

The generated file only changes when codegen runs, so a stale one either misses a new key or still types a key you removed. Run `seedcord codegen` after you attach a plugin, remove one, or rename a key.

When you accept the prompt from `seedcord dev` to re-register your commands, it runs codegen too.

Once codegen has run, your editor offers `db` on `this.core`.

```ts
this.core.
```

Whether the plugin has started when your handler runs is a separate question, which [the lifecycle](/plugins/lifecycle) answers.