I am working on an app to which will using redux saga/persist in react native to manage state and actions. I has set return state correctly, make sure the reducer return TGlobalState, avoid state is undefined with initialState but some how it keep alert error

Type ‘(state: TGlobalState | undefined, action: TActionProp<TGlobalState>) => TGlobalState’ is not assignable to type ‘TGlobalState’.

This is my Global type and reducer to handle update my global state

reducerType.ts

    import {AlphaColorTheme, ColorTheme} from '../../themes/types';
    
    export type TActionProp<T> = {
      type: string;
      payload?: T;
    };
    
    export type TGlobalState = 
    {
      load: boolean;
      colorScheme: ColorTheme;
      colorSchemeAlpha: AlphaColorTheme;
      success: boolean,
      error: boolean,
      successMess: string,
      errorMess: string
    };

globalReducer.ts

    import {lightTheme, lightThemeAlpha} from '../../../themes/colorTheme';
    import {ACTION} from '../../actions/actionTypes';
    import type {TActionProp, TGlobalState} from '../reducerType';
    
    const initialState: TGlobalState = {
      load: false,
      colorScheme: lightTheme,
      colorSchemeAlpha: lightThemeAlpha,
      error: false,
      success: false,
      successMess: '',
      errorMess: '',
    };
    
    const themeReducer = (
      state = initialState,
      action: TActionProp<TGlobalState>,
    ): TGlobalState => {
      switch (action.type) {
        case ACTION.GLOBAL.PENDING.UPDATE_CURRENT_PENDING_STATE:
          return {
            ...state,
            load: action?.payload?.load ?? false,
          };
        
        case ACTION.GLOBAL.THEME.CHANGE_THEME_SUCCESS:
          return {
            ...state,
            load: false,
            colorScheme: action?.payload?.colorScheme ?? lightTheme,
            colorSchemeAlpha: action?.payload?.colorSchemeAlpha ?? lightThemeAlpha,
            success: true,
            successMess: action?.payload?.successMess ?? 'Update Theme successfully',
          };
        
        case ACTION.GLOBAL.THEME.CHANGE_THEME_FAIL:
          return {
            ...state,
            load: false,
            error: action?.payload?.error ?? true,
            errorMess: action?.payload?.errorMess ?? "There's an empty error message in store",
          };
        
        case ACTION.GLOBAL.SUCCESS.UPDATE_SUCCESS_STATE:
          return {
            ...state,
            success: action?.payload?.success ?? true,
            successMess: action?.payload?.successMess ?? "There's an empty success message in store",
          };
        
        case ACTION.GLOBAL.FAILURE.UDPATE_FAILURE_STATE:
          return {
            ...state,
            error: action?.payload?.error ?? false,  // Default to false for error
            errorMess: action?.payload?.errorMess ?? '',  // Default to empty string for error message
          };
        
        default:
          return state;  // Return unmodified state
      }
    };
    
    export default themeReducer;

I have also tried to specify the case for state if it undefined it will return initialState and if not then return state but it not working as i expected

rootReducer.ts

    import {combineReducers} from 'redux';
    import themeReducer from './GlobalReducer';
    import {TGlobalState} from './reducerType';
    
    type IRootReducer = {
      global: TGlobalState;
    };
    
    const rootReducer = combineReducers<IRootReducer>({
      global: themeReducer, 
    });
    
    export default rootReducer;

This is what it alert on my rootReducer

This is the project repository for case if anyone need a more clear vision

I really appreciate for all of your guys help in the future