02.5-backend-handling-exceptions.md

Backend - Handling Exceptions

Creating the AppError Class

• video: https://app.rocketseat.com.br/node/iniciando-back-end-do-app/group/tratando-excecoes/lesson/criando-classe-de-erro
• commit: https://github.com/rocketseat-education/bootcamp-gostack-modulos/commit/618b305f62a4e348a7e7a9ff4f14707d2131c440#diff-2efc37c87c194d03fc0dadbef51f8814
• goals:
  • create a generic AppError class so we can define the HTTP status code in an easier way.

src/errors/AppError.ts:

class AppError {
  public readonly message: string;

  public readonly statusCode: number;

  constructor(message: string, statusCode = 400) {
    this.message = message;
    this.statusCode = statusCode;
  }
}

export default AppError;

Dealing with Errors

• video: https://app.rocketseat.com.br/node/iniciando-back-end-do-app/group/tratando-excecoes/lesson/lidando-com-erros-2
• commit: https://github.com/rocketseat-education/bootcamp-gostack-modulos/tree/master/nivel-02/02-iniciando-back-end-do-app
• goals:
  • create a middleware to handle all exceptions (global exception handler).

yarn add express-async-errors

Remove every try-catch clauses in the source files in src/routes/.

Replace every throw new Error() with throw new AppError().

In the src/server.ts AFTER use()ing the routes, add the global exception handler:

app.use((err: Error, request: Request, response: Response, _: NextFunction) => {
  if (err instanceof AppError) {
    return response.status(err.statusCode).json({
      status: 'error',
      message: err.message,
    });
  }

  console.error(err);

  return response.status(500).json({
    status: 'error',
    message: 'Internal server error',
  });
});

Add this to .eslintrc.json (to ignore the unused vars "errors" in the editor):

// ...
  "rules": {
    // ...
    "@typescript-eslint/no-unused-vars": [
      "error",
      {
        "argsIgnorePattern": "_"
      }
    ]
  },
  // ...

Summary

1. Install express-async-errors
2. Create src/errors/AppError.ts:
3. Remove every try-catch clauses in the source files in src/routes/
4. Replace every throw new Error() with throw new AppError().
5. In the src/server.ts AFTER use()ing the routes, add the global exception handler.

My GoBarber codebase up to this point

https://github.com/meleu/gobarber/tree/9c2a7a36b7950d2a53015466805a742bad6061de