When using a try-catch block to validate an object, why does the Liskov Substitution Principle (LSP) fail to correctly

function parseAndValidate(obj: unknown): ParsedObj | void {
    try {
        // conducting various validations
        return parsedObj
    } catch {
        throw new Error('obj is invalid') 
    } 
} 
const parsedObj = parseAndValidate(obj)

I'm seeking clarification on two points:

  • Why does the LSP identify parsedObj as type any? What's the reason behind this?
  • Why doesn't it identify parsedObj as type ParsedObj, considering that an error will be triggered otherwise?

Due to this, I have to manually specify the type using as ParsedObj.

typescriptlanguage-server-protocol

Answer №1

Oops, I forgot to specify the ParsedObj type!

When using the playground, the parsedObj type should be ParsedObj | void. If you don't declare it, it defaults to any.

Regarding the second question, excluding void will help the LSP recognize that parsedObj always has the type ParsedObj. As mentioned by Julio Di Egidio, use never for self-explanation in such cases, not void. TypeScript will simply disregard it, as Anything | never simplifies to just Anything.

Similar questions

If you have not found the answer to your question or you are interested in this topic, then look at other similar questions below or use the search

How to implement SVG in React with the image source as a parameter?

I've been working on a React component in NextJS that displays an image inside a hexagon. The issue I'm facing is that when I try to use multiple instances of this component with different images in the HexagonWall, all hexagons end up displaying ...

reactjstypescriptsvgnext.jsjsx

Sequelize's bulk synchronization process is ineffective

I am facing an issue with getting sequelize.sync() to function properly. When I call sync() for each model definition individually, it works perfectly fine. However, when trying to execute it from the sequelize instance itself, it seems like the registered ...

node.jstypescriptsequelize.js

Is jest the ideal tool for testing an Angular Library?

I am currently testing an Angular 9 library using Jest. I have added the necessary dependencies for Jest and Typescript in my local library's package.json as shown below: "devDependencies": { "@types/jest": "^25.1.3", "jest": "^25.1.0", ...

javascriptangulartypescriptjestjsangular-library

I am encountering a TypeScript error when using the createRef() method in React JS

Encountering some TypeScript warnings with the following dependencies: <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="8df9f4fde8feeeffe4fdf9cdbea3b8a3bf">[email protected]</a>, <a href="/cdn-cgi/l/email-protect ...

reactjstypescriptmobx-react

I can't seem to catch my Zod error, even though 'express-async-errors' is already installed. What could be causing this issue?

I've been working on developing an API, but I'm facing issues with setting up a global error controller using Zod. It seems that the global error handler is not being called even though I'm using express-async-errors. Below is my error mana ...

node.jstypescriptexpresstypeorm

Creating a unique type with a suffix of `px`

Understanding how to create a Position type class is clear: class Position { x: number = 0; y: number = 0; } However, I now require the x and y values to be integers with the suffix of px, like this: const position = { x: '1px', y: &ap ...

typescript

Tips for setting values to the child component property in Angular 4

When I was using ngif, I encountered an issue with getting the element reference of the child component. After extensive searching, I discovered that in order to access the element, I needed to use view children instead of view child. While I am able to ge ...

angulartypescriptprimeng

Creating a JSX syntax for a simulated component and ensuring it is fully typed with TypeScript

Looking for some innovative ideas on how to approach this challenge. I have a test helper utils with added types: import { jest } from '@jest/globals' import React from 'react' // https://learn.reactnativeschool.com/courses/781007/lect ...

javascriptreactjstypescriptreact-nativejestjs

What are the steps to implement the `serialport` library in `deno`?

After tinkering with Deno to extract readings from an Arduino, I encountered a roadblock when it came to using the serialport library correctly. Here is what I attempted: According to a post, packages from pika.dev should work. However, when trying to use ...

typescriptnpmdenonode-serialport

Is it possible to set up an automatic redirection to the Identity Provider sign-in page when accessing a protected page in Next.js using Auth.js?

Currently in the process of developing a web platform utilizing [email protected] and Auth.js([email protected]). The provider has been configured with the given code, allowing successful signing in using the "Sign in" button. auth.ts import Ne ...

javascripttypescriptnext.jsnext-auth

Terminal displays Typescript variable syntax error

Recently, I've been delving into TypeScript using Visual Studio Code. However, I've encountered a perplexing syntax error that stems from how I've defined a variable. Here's an example of my declaration: let year:number = 2015 My term ...

node.jstypescriptterminalvisual-studio-code

Steps to show the chosen index value in an alert pop-up using Ionic 2 framework

I'm in the process of trying to showcase a selected index value within an Ionic 2 alert box. However, I'm struggling to find the correct method to display it in the Ionic prompt. This pertains to the home.ts import { Component } from '@ang ...

javascriptangulartypescriptionic2angular2-template

Error in Angular 5: Attempting to access 'subscribe' property of undefined variable

I've been struggling for days trying to fix this error on Stack Overflow. Since I'm new to Angular, I decided to reach out to the community for help. The issue revolves around JWT authentication. ERROR TypeError: Cannot read property 'sub ...

node.jsangulartypescriptecmascript-6rxjs

Angular 2: Musing on the potential of Hot Module Replacement and the power of @ngrx/store

If you're just getting started, this link might be helpful: understanding the purpose of HMR. When it comes to managing and designing large projects, I'm still in the early stages and haven't grown a wise beard yet. So, I'm seeking adv ...

angulartypescriptreduxngrxwebpack-hmr

Encountering the "encoding" Module Error when Implementing Nextjs-13 with Supabase

I encountered an issue while trying to utilize Supabase for handling data insertion/retrieval from my form. Upon compilation, I received an error stating that the encoding module was not found. Despite attempting cache cleaning and re-installation of npm m ...

typescriptnpmnext.jssupabase

Guide for retrieving a user object from an HTTP request

I am looking to retrieve only the user object from the request. public async getUserByHash(hash: IHash) { this.logger.log('Hash for check email accessed'); const user = await this.hashRepository.findOne({ select: ['id', ...

typescripttypeorm

activating serverless.yml for aws-xray

I have been attempting to implement AWS X-Ray for all lambda functions in the following manner: serverless.yml provider: tracing: lambda: true apiGateway: true name: aws runtime: nodejs8.10 stage: ${opt:stage, 'dev'} region: ...

node.jstypescriptamazon-web-servicesaws-xray

Analyzing arrays and object key/value pairs based on a specific value in javascript

I want to create a new object with key/value pairs. The new object should include values from an existing key/value object as well as unique values from an array. Here is the array: [{ name: "Computer", name: "Car", name: "House&q ...

javascriptarraystypescriptcomparisonkey-value

Do ES6 features get transpiled into ES5 when utilized in TypeScript?

After implementing ES6 features such as template strings, arrow functions, and destructuring in a TypeScript file, I compile the code to regular JavaScript... Does the TypeScript compiler also compile the ES6 syntax, or do I need to utilize another compil ...

javascripttypescriptecmascript-6

The system now alerts that there are no pending migrations when trying to execute them, which previously ran smoothly without any issues

I am experiencing an issue with my web app where the migrator I have written to create tables and relations is not being recognized by TypeORM, preventing it from running. Here is a glimpse of my file structure (specifically the migrations): src> Data ...

node.jstypescriptpostgresqlnestjstypeorm