Strongly-typed form handlers and validators for Angel.

Validation library based on the matcher library, with Angel support. Why re-invent the wheel, when you can use the same validators you already use for tests?

For convenience's sake, this library also exports matcher.

The basic unit is the Field class, which is a type-safe way to read values from a RequestContext. Here is a simple example of using a TextField instance to read a value from the URL query parameters:

app.get('/hello', (req, res) async {
  var nameField = TextField('name');
  var name = await nameField.getValue(req, query: true); // String
  return 'Hello, $name!';
});

There are several included field types:

• TextField
• BoolField
• NumField
• DoubleField
• IntField
• DateTimeField
• FileField
• ImageField

The Form class lets you combine Field instances, and decode request bodies into Map<String, dynamic>. Unrecognized fields are stripped out of the body, so a Form is effectively a whitelist.

var todoForm = Form(fields: [
  TextField('text'),
  BoolField('is_complete'),
]);

// Validate a request body, and deserialize it immediately.
var todo = await todoForm.deserialize(req, TodoSerializer.fromMap);

// Same as above, but with a Codec<Todo, Map> (i.e. via `angel_serialize`).
var todo = await todoForm.decode(req, todoSerializer);

// Lower-level functionality, typically not called directly.
// Use it if you want to handle validation errors directly, without
// throwing exceptions.

@serializable
class _Todo {
  String text;
  bool isComplete;
}

TODO: Docs about this

This library includes some Matchers for common validations, including:

• isAlphaDash: Asserts that a String is alphanumeric, but also lets it contain dashes or underscores.
• isAlphaNum: Asserts that a String is alphanumeric.
• isBool: Asserts that a value either equals true or false.
• isEmail: Asserts that a String complies to the RFC 5322 e-mail standard.
• isInt: Asserts that a value is an int.
• isNum: Asserts that a value is a num.
• isString: Asserts that a value is a String.
• isNonEmptyString: Asserts that a value is a non-empty String.
• isUrl: Asserts that a String is an HTTPS or HTTP URL.

The remaining functionality is effectively implemented by the matcher package.