fluentvalidation-ts 2.1.0

v2.1.0

on Node.js NPM

This release includes a few bug fixes and small improvements, but also brings in some very useful extensions for the .must rule which make it a lot easier to define custom validation rules and associate custom error messages with them.

Summary

• Updated dev dependencies
• Bug fixes and improvements for the .scalePrecision rule
• Enhanced capability of the .must rule to make it easier to configure reusable custom rules

Updated dev dependencies

All development dependencies have been updated to the latest version.

Bug fixes and improvements for .scalePrecision

• Fixed an issue whereby the validation logic was incorrect for negative numbers
• Improved the implementation under the hood to be more stable
• Added a warning to the documentation regarding floating point arithmetic

New features for .must

This is the big change in this release, which makes it a lot more convenient to define custom validation logic that can be reused across several validators.

Previously it was possible to create reusable validation logic by defining named predicate functions:

// v2.0.0 and below

// Define some custom validation logic:
export const beNumeric = (value: string) => !isNaN(Number(value));

// Then, in the constructor of a validator:
this.ruleFor('stringProperty')
  .must(beNumeric);

This is great, but in order to specify a custom error message we are forced to make a call to .withMessage as well:

// v2.0.0 and below

// Define some custom validation logic:
export const beNumeric = (value: string) => !isNaN(Number(value));
export const beNumericErrorMessage = 'Please enter a number';

// Then, in the constructor of a validator:
this.ruleFor('stringProperty')
  .must(beNumeric)
  .withMessage(beNumericErrorMessage);

This works, but it feels clunky. Ideally we'd have a way of wrapping up both the validation logic and the error message into a single named variable.

Well, v2.1.0 brings exactly that:

// v2.1.0 and above

// Define some custom validation logic:
export const beNumeric = {
  predicate: (value: string) => !isNaN(Number(value)),
  message: 'Please enter a number',
};

// Then, in the constructor of a validator:
this.ruleFor('stringProperty')
  .must(beNumeric);

Not only that, but you can also compose multiple custom rules together into arrays of rules which .must will accept:

// v2.1.0 and above

// Define some custom validation logic:
export const beNumeric = {
  predicate: (value: string) => !isNaN(Number(value)),
  message: 'Please enter a number',
};
export const beAnInteger = {
  predicate: (value: string) => Number(value) % 1 ===0,
  message: 'Please enter a whole number',
};
export const bePositive = {
  predicate: (value: string) => Number(value) > 0,
  message: 'Please enter a positive number',
};
export const bePositiveInteger = [beNumeric, beAnInteger, bePositive];

// Then, in the constructor of a validator:
this.ruleFor('stringProperty')
  .must(bePositiveInteger);

As you can see, these additions to the API of the .must rule open up a ton of new possibilities when it comes to defining custom validation rules. The examples here have only touched on these possibilities - see the README for more details.