ojhaujjwal

TODO

ojhaujjwal

TODO

ojhaujjwal

// Companion code for "The Error Is a Value" (part 2 of the exceptions series).
// `npm run build` typechecks this file (prebuild runs `tsc --noEmit`), so the
// code printed in the post cannot drift from code that compiles.
//
// Trade-off vs the repo's coding standards, kept deliberately: this file
// mirrors the published post 1:1 for series continuity. Boolean `ok`
// discriminator (the exact type part 1 printed), plain tagged-object errors
// rather than `Error` subclasses, the `never` exhaustiveness idiom rather than
// `casesHandled`, and a hand-rolled `pipe` with `any` in its variadic runtime.
// No JSDoc: the post is the documentation.

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type Address = {
  street: string;
  city: string;
  country: string;
};

export type Order = {
  address: Address;
};

ojhaujjwal

Layer Cheat Sheet — Effect v4

Type-safe dependency injection.

Service Tags

Function-style:

const Foo = Context.Service<{
  readonly bar: Effect.Effect<number>

ojhaujjwal

try {
  const doc = await s3.getObject();
} catch (err) {
   // error is any or unknown
   if (err instanceof ObjectNotFoundError) {
     // TODO: handle error
   }
}

ojhaujjwal

import { reduceMap } from './reduce-map';

describe('reduceMap', () => {
  const sumValueAndSubtractKey = (result: number, value: number, key: number) => result + value - key;

  it('should return initial value for empty map', () => {
    expect(
      reduceMap(
        new Map(),
        sumValueAndSubtractKey,

ojhaujjwal

import { Controller, ControllerOptions } from '@nestjs/common';
import { join } from 'path';
import { AuthenticationGuard,  AccessControlGuard } from 'app/guards';

expose function AdminController(options: ControllerOptions) {
  return function (target: Function) {
    Controller(join('/admin', options.path))(target);
    AuthenticationGuard()(target);
    AccessControlGuard({ role: 'admin' })(target);
  };

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@AdminController(options) {
  @Controller({ path: '/admin' + options.path })
  @AuthenticationGuard()
  @AccessControlGuard({ role: 'admin' }) 
}

ojhaujjwal

import { Controller, Get } from '@nestjs/common';
import { AdminController,  AccessControlGuard } from 'app/decorators';

@AdminController({ path: '/dashboard' })
export class AdminDashboardController {
  @Get()
  index(): string {
    return 'dashboard data for admin';
  }
}