CNPJValidator class

A validator that ensures a given string is a valid Brazilian CNPJ.

The CNPJValidator checks whether the provided value follows the Brazilian CNPJ format, which consists of exactly 14 digits (without special characters) or formatted as XX.XXX.XXX/XXXX-XX.

It also verifies:

• The CNPJ is not a repeated sequence (e.g., "00000000000000").
• The two check digits are correctly calculated.

Validation Modes

• ValidationMode.formatted → Expects the CNPJ in the formatted pattern: "XX.XXX.XXX/XXXX-XX"
• ValidationMode.unformatted (default) → Expects only digits: "XXXXXXXXXXXXXX"

Example

final validator = CNPJValidator(message: 'Invalid CNPJ');

print(validator.validate('12.345.678/0001-95')); // null (valid)
print(validator.validate('12345678000195'));     // null (valid)
print(validator.validate('00.000.000/0000-00')); // 'Invalid CNPJ' (invalid)
print(validator.validate('invalid-cnpj'));       // 'Invalid CNPJ' (invalid)
print(validator.validate('11111111111111'));     // 'Invalid CNPJ' (invalid)

Behavior

• Ensures the CNPJ format matches the expected pattern.
• Removes non-digit characters when ValidationMode.unformatted is used.
• Rejects values where all characters are the same (e.g., "00000000000000").
• Validates check digits using the official CNPJ verification algorithm.