Sequelize Integration (in progress)

ds-express-errors can automatically identify and map Sequelize errors into appropriate HTTP errors and responses.

The Sequelize mapper works out of the box using zero-dependency error detection. Sequelize can also be provided through errorClasses to enable strict instanceof detection.

1. Basic integration
2. Supported errors
3. Configuration
4. Strict error detection
5. Example
6. Resulting responses

1. Basic Integration

Use Sequelize normally in your Express application and add the ds-express-errors error handler after all routes.

javascript

Import syntaxES Modules (import)CommonJS (require) Copy

import express from 'express'
import { errorHandler } from 'ds-express-errors'

const app = express();

// Your routes

// Add Error Handler at the very end
app.use(errorHandler);

When a supported Sequelize error reaches errorHandler, ds-express-errors identifies it and maps it to the appropriate HTTP error.

2. Supported Errors

The Sequelize mapper handles validation, constraint, database, connection and timeout errors.

3. Configuration

By default, all available mappers are enabled.

If you want ds-express-errors to use only selected mappers, configure them with needMappers:

javascript

Import syntaxES Modules (import)CommonJS (require) Copy

import { setConfig } from 'ds-express-errors'

setConfig({ needMappers: ['sequelize'] })

4. Strict Error Detection

By default, ds-express-errors follows its zero dependency policy and identifies supported third-party errors without requiring Sequelize as its own dependency.

If stricter error detection is required, Sequelize error classes can be provided through errorClasses.

This allows the library to use the supplied Sequelize classes for error identification instead of relying on the default detection mechanism.

javascript

Import syntaxES Modules (import)CommonJS (require) Copy

import { setConfig } from 'ds-express-errors'
import Sequelize from 'sequelize'

setConfig({ 
  errorClasses: { Sequelize } 
})

When Sequelize is provided, ds-express-errors uses instanceof checks against Sequelize error classes.

For example:

err instanceof Sequelize.UniqueConstraintError 
err instanceof Sequelize.ValidationError 
err instanceof Sequelize.DatabaseError

5. Example

Consider a Sequelize model with a unique email:

javascript

Copy

const User = sequelize.define('User', 
  { 
    email: 
  { 
    type: DataTypes.STRING, 
    allowNull: false, 
    unique: true 
  } 
})

Creating another user with the same email can result in a Sequelize UniqueConstraintError:

javascript

Copy

await User.create({ email: 'user@example.com' })

Once the error reaches errorHandler, ds-express-errors maps it to 409 Conflict.

You do not need to manually check for UniqueConstraintError and create the corresponding HTTP error in every route.

6. Resulting Responses

For a supported Sequelize error, the final response follows the standard ds-express-errors response format. (configured by setConfig())

json

Copy

{ 
	"status": "fail", 
	"message": "Resource already exists" 
}