use PartialDeep

src/base-plugin.ts

 import { Context } from 'koishi';
 import { InjectConfig } from './decorators';
 
-export class BasePlugin<C, PC = Partial<C>> {
+export type PartialDeep<T> = T extends
+  | string
+  | number
+  | bigint
+  | boolean
+  | null
+  | undefined
+  | symbol
+  | Date
+  ? T | undefined
+  : // Arrays, Sets and Maps and their readonly counterparts have their items made
+  // deeply partial, but their own instances are left untouched
+  T extends Array<infer ArrayType>
+  ? Array<PartialDeep<ArrayType>>
+  : T extends ReadonlyArray<infer ArrayType>
+  ? ReadonlyArray<ArrayType>
+  : T extends Set<infer SetType>
+  ? Set<PartialDeep<SetType>>
+  : T extends ReadonlySet<infer SetType>
+  ? ReadonlySet<SetType>
+  : T extends Map<infer KeyType, infer ValueType>
+  ? Map<PartialDeep<KeyType>, PartialDeep<ValueType>>
+  : T extends ReadonlyMap<infer KeyType, infer ValueType>
+  ? ReadonlyMap<PartialDeep<KeyType>, PartialDeep<ValueType>>
+  : // ...and finally, all other objects.
+    {
+      [K in keyof T]?: PartialDeep<T[K]>;
+    };
+
+export class BasePlugin<C, PC = PartialDeep<C>> {
   constructor(protected ctx: Context, config: PC) {}
 
   @InjectConfig()