codesnips
go 18 lines · 1 tab

Error wrapping that stays inspectable with errors.Is and errors.As

Leah Thompson Jan 2026
1 tab 
package domain

import (
  "errors"
  "fmt"
)

var (
  ErrNotFound = errors.New("not found")
  ErrConflict = errors.New("conflict")
)

func WrapNotFound(resource string, cause error) error {
  if cause == nil {
    return fmt.Errorf("%s: %w", resource, ErrNotFound)
  }
  return fmt.Errorf("%s: %w: %w", resource, ErrNotFound, cause)
}
1 file · go Explain with highlit

In production, you want errors that are both human-readable and machine-checkable. I wrap errors with %w so callers can still match them using errors.Is and errors.As. This avoids string comparisons like if err.Error() == ..., which break on refactors. I also like defining sentinel errors for well-known conditions (ErrNotFound, ErrConflict) and returning them from lower layers with context using fmt.Errorf. The service layer can then map those to HTTP status codes without losing the original cause. The important discipline is consistency: don’t mix ad-hoc errors with sentinel errors for the same condition. If you follow that rule, you get clean logs and predictable error handling across the codebase.

Related snips

go 
package api

import (
  "net/http"
  "runtime/debug"
)

Expose build metadata for debugging deploys

go observability build
by Leah Thompson 1 tab
ruby 
payload = {
  sub: user.id,
  iss: 'https://auth.example.com',
  aud: 'codesnips-api',
  exp: 15.minutes.from_now.to_i,
  iat: Time.now.to_i,

JWT issuance and verification without common footguns

jwt authentication api
by Kai Nakamura 2 tabs
ruby 
module Api
  module V1
    class UsersController < BaseController
      def show
        user = User.includes(:profile).find(params[:id])

ETags for conditional requests and caching

rails caching http-caching
by Alex Kumar 1 tab
go 
package dbutil

import (
  "context"

  "github.com/jackc/pgconn"

Retry Postgres serialization failures with bounded attempts

go postgres transactions
by Leah Thompson 1 tab
graphql 
type User {
    id: ID!
    name: String!
    email: String!
    posts: [Post!]!
    createdAt: String!

GraphQL API with Spring Boot

java graphql spring-boot
by David Kumar 3 tabs
typescript 
import axios, { AxiosError } from 'axios'
import { v4 as uuidv4 } from 'uuid'

const api = axios.create({
  baseURL: import.meta.env.VITE_API_URL || 'http://localhost:3000/api/v1',
  timeout: 15000,

Axios API client with interceptors

react axios api
by Maya Patel 1 tab

Share this code

Here's the card — post it anywhere.

Error wrapping that stays inspectable with errors.Is and errors.As — share card
Link copied