Hono Error Handler is a custom error handler middleware for the Hono web framework. It allows you to define and use your own error handling functions while providing some default error handling behavior.

1. Installation
2. Usage
   • Creating Error Handlers
   • Adding The Error Handler To Your App
   • Throwing Custom Errors In Routes
3. Custom Response Handler
4. Parameters
   • errorHandler Parameters
   • ErrorResponse Parameters
5. Contributing

You can install the package with:

npm install hono-error-handler
yarn add hono-error-handler
bun install hono-error-handler

Simplify error handling in your hono applications with the hono-error-handler package. This package streamlines error management within your route handlers by providing an easy way to create custom errors with associated status codes using ErrorResponse. By using the errorHandler, you can eliminate the need for extensive try-catch blocks in your routes, resulting in cleaner and more maintainable code. Additionally, the errorHandler ensures consistent error responses in any format across your application. If you need to throw errors in your routes, ErrorResponse simplifies the process.

Without any custom error handlers defined, the default behavior is to return a 500 Internal Server Error response in JSON.

Syntax: The function is defined as follows:

import { Error } from 'hono-error-handler';

const handleMongooseErrors = (error: Error) => {
  // Error handling logic here
};

(error: Error) => declares an arrow function that takes one parameter named error, which is of type Error.

• Parameter (error: Error): The error parameter represents an error object that is expected to conform to the Error interface. This error will be passed to your function automatically.

• Using If Statements: Inside the function, there are multiple if statements that check for specific conditions related to your error types. These conditions are used to identify and handle different error scenarios.

• Return: When a specific condition is met, the function modifies the error object to provide a more informative error message and sets an appropriate status code. For example:

// Mongoose bad ObjectId
if (error.name === 'CastError') {
  error.message = 'Resource not found';
  error.statusCode = 404;
  return error;
}

In this case, if the error's name property matches 'CastError', the function updates the error object's message and statusCode properties and immediately returns the modified error object.

• Default Return: At the end of the function, there's a default return statement:

return error;

This default return ensures that if none of the specific conditions are met (i.e., the error doesn't match any known Mongoose error type), the original error object is returned without modification.

Here is a full example of a custom error handler with mongoose:

import { Error } from 'hono-error-handler';

const handleMongooseErrors = (error: Error) => {
  // Mongoose bad ObjectId
  if (error.name === 'CastError') {
    error.message = 'Resource not found';
    error.statusCode = 404;
    return error;
  }

  // Mongoose duplicate key
  if (error.code === 11000) {
    const field = Object.keys(error.keyValue)[0];
    error.message = `${field} is already registered`;
    error.statusCode = 409;
    return error;
  }

  // Mongoose validation error
  if (error.name === 'ValidationError') {
    let message = '';
    Object.values(error.errors).map((val: any) => {
      message += `${val.message},`;
    });
    error.message = message;
    error.statusCode = 400;
    return error;
  }

  return error;
};

export default handleMongooseErrors;

Import the error handler

import { errorHandler } from 'hono-error-handler';

Import your custom error handler function:

import handleMongooseErrors from './handleMongooseErrors';

Create an array of your custom error handlers. This array will be passed to the errorHandler function.

const errorHandlers = [handleMongooseErrors, additionalErrorhander];

Set up the error handler for your app. Pass in the errorHandlers array as the first argument to errorHandler. Optionally, you can also specify a custom response with the Custom Response Handler.

app.onError(errorHandler(errorHandlers));

Import the ErrorResponse class:

import { ErrorResponse } from 'hono-error-handler';

In your route handler, when you encounter a condition that should result in an error response, create a new instance of ErrorResponse. Provide the error message and status code as arguments to the constructor. For example:

app.get('/exmaple', (c) => {
  // Check some condition
  if (someConditionIsNotMet) {
    // Throw a custom error using ErrorResponse
    throw new ErrorResponse('Resource not found', 404);
  }

  // Your regular route logic
  // ...
});

This will bypass the errorHandler and immediately send the response

An optional custom response handler in the hono-error-handler package allows you to define how error responses are formatted and sent back to clients when an error occurs. To create a custom response handler, follow these steps:

Define a function that takes two parameters:

• error: An object conforming to the FormattedError interface.
• c: The Hono Context Object.

The function will be responsible for constructing and sending the error response based on the provided error object.

Syntax:

app.onError(errorHandler(myErrorHandler, (error, c) => {
 return c.json({
   error: error.message, 
 }, 
    error.statusCode,
 )
}));

• (error: FormattedError, c: Context) => declares an arrow function that takes two parameters: error and c. error is expected to be of type FormattedError, and c is the Hono Context object.

If you would like to create your response handler in a separate file you can do the following.

import { ResponseHandler } from 'hono-error-handler';

const customReponseHandler: ResponseHandler = (error: FormattedError, c: Context) => {
   return c.json({
              error: error.message,
           },
           error.statusCode,
   );
};

If you do not specify a custom response, the response will show in this format:

return c.json({
    success: false,
    message: error.message
  },
    error.statusCode
  )

We welcome contributions from the community to enhance and improve the hono-error-handler package. If you'd like to contribute, please follow these steps:

1. Fork the Repository: Start by forking the hono-error-handler repository on GitHub to your own GitHub account.

2. Clone the Repository: Clone the forked repository to your local development environment:

   git clone https://github.com/your-username/hono-error-handler.git

3. Create a New Branch: Create a new branch for your contribution. Use a descriptive branch name that reflects the nature of your changes:

   git checkout -b your-feature-name

4. Make Changes: Implement your changes or additions to the codebase. Ensure that your code follows the project's coding style and conventions.

5. Test Your Changes: Run tests to make sure your changes do not introduce new issues.

6. Commit Changes: Commit your changes with a clear and concise commit message:

   git commit -m "feat: Add new feature" (or "fix: Fix issue #123")

7. Push Changes: Push your branch to your forked repository on GitHub:

   git push origin your-feature-name

8. Create a Pull Request: Go to the hono-error-handler repository on GitHub, and you should see a "New Pull Request" button. Click it, and create a pull request from your forked branch to the main repository.

9. Discuss and Review: Participate in discussions and reviews related to your pull request. Make any necessary updates based on feedback from maintainers and contributors.

10. Merge and Deploy: Once your pull request is approved, it will be merged into the main repository. The changes will be deployed in future releases.

Thank you for contributing to hono-error-handler! Your contributions help make the package better for everyone.