fix(types): add schema plugin option inference

test/types/schema.test.ts

@@ -702,3 +702,38 @@ function gh12030() {
   }>({} as InferSchemaType<typeof Schema6>);
 
 }
+
+function pluginOptions() {
+  interface SomePluginOptions {
+    option1?: string;
+    option2: number;
+  }
+
+  function pluginFunction(schema: Schema<any>, options: SomePluginOptions) {
+    return; // empty function, to satisfy lint option
+  }
+
+  const schema = new Schema({});
+  expectType<Schema<any>>(schema.plugin(pluginFunction)); // test that chaining would be possible
+
+  // could not add strict tests that the parameters are inferred correctly, because i dont know how this would be done in tsd
+
+  // test basic inferrence
+  expectError(schema.plugin(pluginFunction, {})); // should error because "option2" is not optional
+  schema.plugin(pluginFunction, { option2: 0 });
+  schema.plugin(pluginFunction, { option1: 'string', option2: 1 });
+  expectError(schema.plugin(pluginFunction, { option1: 'string' })); // should error because "option2" is not optional
+  expectError(schema.plugin(pluginFunction, { option2: 'string' })); // should error because "option2" type is "number"
+  expectError(schema.plugin(pluginFunction, { option1: 0 })); // should error because "option1" type is "string"
+
+  // test plugins without options defined
+  function pluginFunction2(schema: Schema<any>) {
+    return; // empty function, to satisfy lint option
+  }
+  schema.plugin(pluginFunction2);
+  expectError(schema.plugin(pluginFunction2, {})); // should error because no options argument is defined
+
+  // test overwriting options
+  schema.plugin<any, SomePluginOptions>(pluginFunction2, { option2: 0 });
+  expectError(schema.plugin<any, SomePluginOptions>(pluginFunction2, {})); // should error because "option2" is not optional
+}

types/index.d.ts

@@ -157,6 +157,8 @@ declare module 'mongoose' {
 
   type QueryResultType<T> = T extends Query<infer ResultType, any> ? ResultType : never;
 
+  type PluginFunction<DocType> = (schema: Schema<DocType>, opts?: any) => void;
+
   export class Schema<EnforcedDocType = any, M = Model<EnforcedDocType, any, any, any>, TInstanceMethods = {}, TQueryHelpers = {}, TVirtuals = {},
     TStaticMethods = {},
     TPathTypeKey extends TypeKeyBaseType = DefaultTypeKey,
@@ -239,7 +241,7 @@ declare module 'mongoose' {
     pathType(path: string): string;
 
     /** Registers a plugin for this schema. */
-    plugin(fn: (schema: Schema<DocType>, opts?: any) => void, opts?: any): this;
+    plugin<PFunc extends PluginFunction<DocType>, POptions extends Parameters<PFunc>[1] = Parameters<PFunc>[1]>(fn: PFunc, opts?: POptions): this;
 
     /** Defines a post hook for the model. */
     post<T = HydratedDocument<DocType, TInstanceMethods>>(method: MongooseDocumentMiddleware | MongooseDocumentMiddleware[] | RegExp, fn: PostMiddlewareFunction<T, T>): this;