fix(types): align the return value of increment and decrement with ac…

…tual behavior (#14704)

src/model.d.ts

@@ -2831,18 +2831,18 @@ export abstract class Model<TModelAttributes extends {} = any, TCreationAttribut
    *   value of `by` given in options. If an array is provided, the same is true for each column.
    *   If an object is provided, each key is incremented by the corresponding value, `by` is ignored.
    *
-   * @returns an array of affected rows and affected count with `options.returning` true, whenever supported by dialect
+   * @returns an array of affected rows or with affected count if `options.returning` is true, whenever supported by dialect
    */
   static increment<M extends Model>(
     this: ModelStatic<M>,
     fields: AllowReadonlyArray<keyof Attributes<M>>,
     options: IncrementDecrementOptionsWithBy<Attributes<M>>
-  ): Promise<[affectedRows: M[]]>;
+  ): Promise<[affectedRows: M[], affectedCount?: number]>;
   static increment<M extends Model>(
     this: ModelStatic<M>,
     fields: { [key in keyof Attributes<M>]?: number },
     options: IncrementDecrementOptions<Attributes<M>>
-  ): Promise<[affectedRows: M[]]>;
+  ): Promise<[affectedRows: M[], affectedCount?: number]>;
 
   /**
    * Decrements the value of one or more attributes.
@@ -2853,20 +2853,20 @@ export abstract class Model<TModelAttributes extends {} = any, TCreationAttribut
    *   value of `by` given in options. If an array is provided, the same is true for each column.
    *   If an object is provided, each key is incremented by the corresponding value, `by` is ignored.
    *
-   * @returns an array of affected rows and affected count with `options.returning` true, whenever supported by dialect
+   * @returns an array of affected rows or with affected count if `options.returning` is true, whenever supported by dialect
    *
    * @since 4.36.0
    */
   static decrement<M extends Model>(
     this: ModelStatic<M>,
     fields: AllowReadonlyArray<keyof Attributes<M>>,
     options: IncrementDecrementOptionsWithBy<Attributes<M>>
-  ): Promise<M>;
+  ): Promise<[affectedRows: M[], affectedCount?: number]>;
   static decrement<M extends Model>(
     this: ModelStatic<M>,
     fields: { [key in keyof Attributes<M>]?: number },
     options: IncrementDecrementOptions<Attributes<M>>
-  ): Promise<M>;
+  ): Promise<[affectedRows: M[], affectedCount?: number]>;
 
   /**
    * A hook that is run before validation

test/types/model.ts

@@ -87,6 +87,30 @@ MyModel.count({ group: 'type' }).then(result => {
   expectTypeOf(result[0]).toMatchTypeOf<{ count: number }>();
 });
 
+MyModel.increment('int', { by: 1 }).then(result => {
+  expectTypeOf(result).toEqualTypeOf<[affectedRows: MyModel[], affectedCount?: number]>();
+});
+
+MyModel.increment({ int: 2 }, {}).then(result => {
+  expectTypeOf(result).toEqualTypeOf<[affectedRows: MyModel[], affectedCount?: number]>();
+});
+
+MyModel.increment(['int'], { by: 3 }).then(result => {
+  expectTypeOf(result).toEqualTypeOf<[affectedRows: MyModel[], affectedCount?: number]>();
+});
+
+MyModel.decrement('int', { by: 1 }).then(result => {
+  expectTypeOf(result).toEqualTypeOf<[affectedRows: MyModel[], affectedCount?: number]>();
+});
+
+MyModel.decrement({ int: 2 }, {}).then(result => {
+  expectTypeOf(result).toEqualTypeOf<[affectedRows: MyModel[], affectedCount?: number]>();
+});
+
+MyModel.decrement(['int'], { by: 3 }).then(result => {
+  expectTypeOf(result).toEqualTypeOf<[affectedRows: MyModel[], affectedCount?: number]>();
+});
+
 MyModel.build({ int: 10 }, { include: OtherModel });
 
 MyModel.bulkCreate([{ int: 10 }], { include: OtherModel, searchPath: 'public' });
@@ -109,7 +133,7 @@ MyModel.update({}, { where: { str: 'bar' }, returning: ['str'] }).then(result =>
 
 const sequelize = new Sequelize('mysql://user:user@localhost:3306/mydb');
 
-const model: typeof MyModel = MyModel.init({
+MyModel.init({
   int: DataTypes.INTEGER,
   str: DataTypes.STRING,
   virtual: {