docs(either-errors): snippets and content

Author: kgajowy

articles/either-errors/README.md

@@ -1,73 +1,23 @@
 <p align="center">
-  <a href="http://nestjs.com/" target="blank"><img src="https://nestjs.com/img/logo_text.svg" width="320" alt="Nest Logo" /></a>
+    <a href="https://www.angular.love/" target="_blank"><img src="https://www.angular.love/wp-content/uploads/2020/07/logo-angular.png" alt="angular love"/></a>
 </p>
 
-[circleci-image]: https://img.shields.io/circleci/build/github/nestjs/nest/master?token=abc123def456
-[circleci-url]: https://circleci.com/gh/nestjs/nest
+# Either & Error handling
 
-  <p align="center">A progressive <a href="http://nodejs.org" target="_blank">Node.js</a> framework for building efficient and scalable server-side applications.</p>
-    <p align="center">
-<a href="https://www.npmjs.com/~nestjscore" target="_blank"><img src="https://img.shields.io/npm/v/@nestjs/core.svg" alt="NPM Version" /></a>
-<a href="https://www.npmjs.com/~nestjscore" target="_blank"><img src="https://img.shields.io/npm/l/@nestjs/core.svg" alt="Package License" /></a>
-<a href="https://www.npmjs.com/~nestjscore" target="_blank"><img src="https://img.shields.io/npm/dm/@nestjs/common.svg" alt="NPM Downloads" /></a>
-<a href="https://circleci.com/gh/nestjs/nest" target="_blank"><img src="https://img.shields.io/circleci/build/github/nestjs/nest/master" alt="CircleCI" /></a>
-<a href="https://coveralls.io/github/nestjs/nest?branch=master" target="_blank"><img src="https://coveralls.io/repos/github/nestjs/nest/badge.svg?branch=master#9" alt="Coverage" /></a>
-<a href="https://discord.gg/G7Qnnhy" target="_blank"><img src="https://img.shields.io/badge/discord-online-brightgreen.svg" alt="Discord"/></a>
-<a href="https://opencollective.com/nest#backer" target="_blank"><img src="https://opencollective.com/nest/backers/badge.svg" alt="Backers on Open Collective" /></a>
-<a href="https://opencollective.com/nest#sponsor" target="_blank"><img src="https://opencollective.com/nest/sponsors/badge.svg" alt="Sponsors on Open Collective" /></a>
-  <a href="https://paypal.me/kamilmysliwiec" target="_blank"><img src="https://img.shields.io/badge/Donate-PayPal-ff3f59.svg"/></a>
-    <a href="https://opencollective.com/nest#sponsor"  target="_blank"><img src="https://img.shields.io/badge/Support%20us-Open%20Collective-41B883.svg" alt="Support us"></a>
-  <a href="https://twitter.com/nestframework" target="_blank"><img src="https://img.shields.io/twitter/follow/nestframework.svg?style=social&label=Follow"></a>
-</p>
-  <!--[![Backers on Open Collective](https://opencollective.com/nest/backers/badge.svg)](https://opencollective.com/nest#backer)
-  [![Sponsors on Open Collective](https://opencollective.com/nest/sponsors/badge.svg)](https://opencollective.com/nest#sponsor)-->
-
-## Description
-
-[Nest](https://github.com/nestjs/nest) framework TypeScript starter repository.
-
-## Installation
-
-```bash
-$ npm install
-```
-
-## Running the app
-
-```bash
-# development
-$ npm run start
-
-# watch mode
-$ npm run start:dev
-
-# production mode
-$ npm run start:prod
-```
-
-## Test
-
-```bash
-# unit tests
-$ npm run test
+## Notable libraries
 
-# e2e tests
-$ npm run test:e2e
+💖 `fp-ts` for streaming rows from postgres db
 
-# test coverage
-$ npm run test:cov
-```
+💖 `@nestjs-architects/typed-cqrs` for a little more safety
 
-## Support
+💖 `utility-types` for the sake of principle
 
-Nest is an MIT-licensed open source project. It can grow thanks to the sponsors and support by the amazing backers. If you'd like to join them, please [read more here](https://docs.nestjs.com/support).
+💖 ... and of course: `nestjs`
 
-## Stay in touch
+## Running
 
-- Author - [Kamil Myśliwiec](https://kamilmysliwiec.com)
-- Website - [https://nestjs.com](https://nestjs.com/)
-- Twitter - [@nestframework](https://twitter.com/nestframework)
+* run the application `npm run start`
 
-## License
+## Tests
 
-Nest is [MIT licensed](LICENSE).
+* `npm run test:e2e`

articles/either-errors/snippets/01-either-declaration.png

@@ -0,0 +1,13 @@
+# Wyraź swoje metody!
+
+Zachodzisz w głowę, czy i jakie błędy może zwrócić funkcja? Ułatw życie sobie i innym poprzez ekspresję intencji!
+
+![Returning Either](01-either-declaration.png)
+
+([Zobacz w praktyce!](link do repo))
+
+# Skoro wyjątek może być wartością, to czym?
+
+`enum`? `Symbol`? Przewagą `Symbol` jest możliwość uni typów.
+
+![Symbol vs enum](02-symbol-enum.png)

articles/either-errors/snippets/02-symbol-enum.png

@@ -12,6 +12,6 @@ export class ReturnBookHandler implements IInferredCommandHandler<ReturnBook> {
     if (isbn !== outOfStockIsbn && isbn !== limitReachedIsbn) {
       return left(TimeLimitExceeded);
     }
-    return right(undefined);
+    return right(null);
   }
 }