Error handling

Objection throws four kinds of errors:

1. ValidationError when an input that could come from the outside world is invalid. These inputs include model instances and POJOs, relation expressions, object graphs etc. ValidationError has a type property that can be used to distinguish between the different error types.

2. NotFoundError when throwIfNotFound was called for a query and no results were found.

3. Database errors as defined by the db-errors library (opens new window). You can access the error classes through objection. See the example.

4. A basic JavaScript Error when a programming or logic error is detected. In these cases there is nothing the users can do and the only correct way to handle the error is to send a 500 response to the user and to fix the program.

Examples

An example error handler function that handles all possible errors. Note that you should never send the errors directly to the client as they may contain SQL and other information that reveals too much about the inner workings of your app.

const {
  ValidationError,
  NotFoundError,
  DBError,
  ConstraintViolationError,
  UniqueViolationError,
  NotNullViolationError,
  ForeignKeyViolationError,
  CheckViolationError,
  DataError
} = require('objection');

// In this example `res` is an express response object.
function errorHandler(err, res) {
  if (err instanceof ValidationError) {
    switch (err.type) {
      case 'ModelValidation':
        res.status(400).send({
          message: err.message,
          type: err.type,
          data: err.data
        });
        break;
      case 'RelationExpression':
        res.status(400).send({
          message: err.message,
          type: 'RelationExpression',
          data: {}
        });
        break;
      case 'UnallowedRelation':
        res.status(400).send({
          message: err.message,
          type: err.type,
          data: {}
        });
        break;
      case 'InvalidGraph':
        res.status(400).send({
          message: err.message,
          type: err.type,
          data: {}
        });
        break;
      default:
        res.status(400).send({
          message: err.message,
          type: 'UnknownValidationError',
          data: {}
        });
        break;
    }
  } else if (err instanceof NotFoundError) {
    res.status(404).send({
      message: err.message,
      type: 'NotFound',
      data: {}
    });
  } else if (err instanceof UniqueViolationError) {
    res.status(409).send({
      message: err.message,
      type: 'UniqueViolation',
      data: {
        columns: err.columns,
        table: err.table,
        constraint: err.constraint
      }
    });
  } else if (err instanceof NotNullViolationError) {
    res.status(400).send({
      message: err.message,
      type: 'NotNullViolation',
      data: {
        column: err.column,
        table: err.table
      }
    });
  } else if (err instanceof ForeignKeyViolationError) {
    res.status(409).send({
      message: err.message,
      type: 'ForeignKeyViolation',
      data: {
        table: err.table,
        constraint: err.constraint
      }
    });
  } else if (err instanceof CheckViolationError) {
    res.status(400).send({
      message: err.message,
      type: 'CheckViolation',
      data: {
        table: err.table,
        constraint: err.constraint
      }
    });
  } else if (err instanceof DataError) {
    res.status(400).send({
      message: err.message,
      type: 'InvalidData',
      data: {}
    });
  } else if (err instanceof DBError) {
    res.status(500).send({
      message: err.message,
      type: 'UnknownDatabaseError',
      data: {}
    });
  } else {
    res.status(500).send({
      message: err.message,
      type: 'UnknownError',
      data: {}
    });
  }
}