checker

README

Checker

Checker is a Go library that helps you validate user input. It can be used to validate user input stored in a struct, or to validate individual pieces of input.

There are many validation libraries available, but I prefer to build my own tools and avoid pulling in unnecessary dependencies. That's why I created Checker, a simple validation library with no dependencies. It's easy to use and gets the job done.

Usage

To get started, install the Checker library with the following command:

go get github.com/cinar/checker

Next, you will need to import the library into your source file. You can do this by following the example below:

import (
    "github.com/cinar/checker"
)

Validating User Input Stored in a Struct

Checker can be used in two ways. The first way is to validate user input stored in a struct. To do this, you can list the checkers through the struct tag for each field. Here is an example:

type Person struct {
    Name string `checkers:"required"`
}

person := &Person{}

mistakes, valid := checker.Check(person)
if !valid {
    // Send the mistakes back to the user
}

Validating Individual User Input

If you do not want to validate user input stored in a struct, you can individually call the checker functions to validate the user input. Here is an example:

var name

result := checker.IsRequired(name)
if result != ResultValid {
    // Send the result back to the user
}

Normalizers and Checkers

Checkers are used to check for problems in user input, while normalizers are used to transform user input into a preferred format. For example, a normalizer could be used to trim spaces from the beginning and end of a string, or to convert a string to title case.

I am not entirely happy with the decision to combine checkers and normalizers into a single library, but using them together can be useful. Normalizers and checkers can be mixed in any order when defining the validation steps for user data. For example, the trim normalizer can be used in conjunction with the required checker to first trim the user input and then check if the user provided the required information. Here is an example:

type Person struct {
    Name string `checkers:"trim required"`
}

Checkers Provided

This package currently provides the following checkers:

• alphanumeric checks if the given string consists of only alphanumeric characters.
• ascii checks if the given string consists of only ASCII characters.
• cidr checker checks if the value is a valid CIDR notation IP address and prefix length.
• credit-card checks if the given value is a valid credit card number.
• digits checks if the given string consists of only digit characters.
• email checks if the given string is an email address.
• fqdn checks if the given string is a fully qualified domain name.
• ip checks if the given value is an IP address.
• ipv4 checks if the given value is an IPv4 address.
• ipv6 checks if the given value is an IPv6 address.
• luhn checks if the given number is valid based on the Luhn algorithm.
• mac checks if the given value is a valid an IEEE 802 MAC-48, EUI-48, EUI-64, or a 20-octet IP over InfiniBand link-layer address.
• max checks if the given value is less than the given maximum.
• max-length checks if the length of the given value is less than the given maximum length.
• min checks if the given value is greather than the given minimum.
• min-length checks if the length of the given value is greather than the given minimum length.
• regexp checks if the given string matches the regexp pattern.
• required checks if the required value is provided.
• same checks if the given value is equal to the value of the field with the given name.

Normalizers Provided

This package currently provides the following normalizers. They can be mixed with the checkers when defining the validation steps for user data.

• lower maps all Unicode letters in the given value to their lower case.
• upper maps all Unicode letters in the given value to their upper case.
• title maps the first letter of each word to their upper case.
• trim removes the whitespaces at the beginning and at the end of the given value.
• trim-left removes the whitespaces at the beginning of the given value.
• trim-right removes the whitespaces at the end of the given value.

Custom Checkers

To define a custom checker, you need to create a new function with the following parameters:

func CustomChecker(value, parent reflect.Value) Result {
    return ResultValid
}

type MakeFunc You also need to create a make function that takes the checker configuration and returns a reference to the checker function.

func CustomMaker(params string) CheckFunc {
    return CustomChecker
}

Finally, you need to call the Register function to register your custom checker.

checker.Register("custom-checker", CustomMaker)

Once you have registered your custom checker, you can use it by simply specifying its name.

type User struct {
    Username string `checkers:"custom-checker"`
}

Contributing to the Project

Anyone can contribute to Checkers library. Please make sure to read our Contributor Covenant Code of Conduct guide first. Follow the How to Contribute to Checker to contribute.

License

This library is free to use, modify, and distribute under the terms of the MIT license. The full license text can be found in the LICENSE file.

The MIT license is a permissive license that allows you to do almost anything with the library, as long as you retain the copyright notice and the license text. This means that you can use the library in commercial products, modify it, and redistribute it without having to ask for permission from the authors.

The LICENSE file is located in the root directory of the library. You can open it in a text editor to read the full license text.

Documentation

Overview

Package checker is a Go library for validating user input through struct tags.

Index

• Constants
• func FailIfNoPanic(t *testing.T)
• func Register(name string, maker MakeFunc)
• type CheckFunc
  • func MakeRegexpChecker(expression string, invalidResult Result) CheckFunc
• type MakeFunc
  • func MakeRegexpMaker(expression string, invalidResult Result) MakeFunc
• type Mistakes
  • func Check(s interface{}) (Mistakes, bool)
• type Result
  • func IsASCII(value string) Result
  • func IsAlphanumeric(value string) Result
  • func IsAmexCreditCard(number string) Result
  • func IsAnyCreditCard(number string) Result
  • func IsCidr(value string) Result
  • func IsDigits(value string) Result
  • func IsDinersCreditCard(number string) Result
  • func IsDiscoveryCreditCard(number string) Result
  • func IsEmail(email string) Result
  • func IsFqdn(domain string) Result
  • func IsIP(value string) Result
  • func IsIPV4(value string) Result
  • func IsIPV6(value string) Result
  • func IsJcbCreditCard(number string) Result
  • func IsLuhn(number string) Result
  • func IsMac(value string) Result
  • func IsMasterCardCreditCard(number string) Result
  • func IsMax(value interface{}, max float64) Result
  • func IsMaxLength(value interface{}, maxLength int) Result
  • func IsMin(value interface{}, min float64) Result
  • func IsMinLength(value interface{}, minLength int) Result
  • func IsRequired(v interface{}) Result
  • func IsUnionPayCreditCard(number string) Result
  • func IsVisaCreditCard(number string) Result

Constants

const CheckerASCII = "ascii"

CheckerASCII is the name of the checker.

const CheckerAlphanumeric = "alphanumeric"

CheckerAlphanumeric is the name of the checker.

const CheckerCidr = "cidr"

CheckerCidr is the name of the checker.

const CheckerCreditCard = "credit-card"

CheckerCreditCard is the name of the checker.

const CheckerDigits = "digits"

CheckerDigits is the name of the checker.

const CheckerEmail = "email"

CheckerEmail is the name of the checker.

const CheckerFqdn = "fqdn"

CheckerFqdn is the name of the checker.

const CheckerIP = "ip"

CheckerIP is the name of the checker.

const CheckerIPV4 = "ipv4"

CheckerIPV4 is the name of the checker.

const CheckerIPV6 = "ipv6"

CheckerIPV6 is the name of the checker.

const CheckerLuhn = "luhn"

CheckerLuhn is the name of the checker.

const CheckerMac = "mac"

CheckerMac is the name of the checker.

const CheckerMax = "max"

CheckerMax is the name of the checker.

const CheckerMaxLength = "max-length"

CheckerMaxLength is the name of the checker.

const CheckerMin = "min"

CheckerMin is the name of the checker.

const CheckerMinLength = "min-length"

CheckerMinLength is the name of the checker.

const CheckerRegexp = "regexp"

CheckerRegexp is the name of the checker.

const CheckerRequired = "required"

CheckerRequired is the name of the checker.

const CheckerSame = "same"

CheckerSame is the name of the checker.

const NormalizerLower = "lower"

NormalizerLower is the name of the normalizer.

const NormalizerTitle = "title"

NormalizerTitle is the name of the normalizer.

const NormalizerTrim = "trim"

NormalizerTrim is the name of the normalizer.

const NormalizerTrimLeft = "trim-left"

NormalizerTrimLeft is the name of the normalizer.

const NormalizerTrimRight = "trim-right"

NormalizerTrimRight is the name of the normalizer.

const NormalizerUpper = "upper"

NormalizerUpper is the name of the normalizer.

const ResultNotASCII = "NOT_ASCII"

ResultNotASCII indicates that the given string contains non-ASCII characters.

const ResultNotAlphanumeric = "NOT_ALPHANUMERIC"

ResultNotAlphanumeric indicates that the given string contains non-alphanumeric characters.

const ResultNotCidr = "NOT_CIDR"

ResultNotCidr indicates that the given value is not a valid CIDR.

const ResultNotCreditCard = "NOT_CREDIT_CARD"

ResultNotCreditCard indicates that the given value is not a valid credit card number.

const ResultNotDigits = "NOT_DIGITS"

ResultNotDigits indicates that the given string contains non-digit characters.

const ResultNotEmail = "NOT_EMAIL"

ResultNotEmail indicates that the given string is not a valid email.

const ResultNotFqdn = "NOT_FQDN"

ResultNotFqdn indicates that the given string is not a valid FQDN.

const ResultNotIP = "NOT_IP"

ResultNotIP indicates that the given value is not an IP address.

const ResultNotIPV4 = "NOT_IP_V4"

ResultNotIPV4 indicates that the given value is not an IPv4 address.

const ResultNotIPV6 = "NOT_IP_V6"

ResultNotIPV6 indicates that the given value is not an IPv6 address.

const ResultNotLuhn = "NOT_LUHN"

ResultNotLuhn indicates that the given number is not valid based on the Luhn algorithm.

const ResultNotMac = "NOT_MAC"

ResultNotMac indicates that the given value is not an MAC address.

const ResultNotMatch = "NOT_MATCH"

ResultNotMatch indicates that the given string does not match the regexp pattern.

const ResultNotMax = "NOT_MIN"

ResultNotMax indicates that the given value is above the defined maximum.

const ResultNotMaxLength = "NOT_MAX_LENGTH"

ResultNotMaxLength indicates that the length of the given value is above the defined number.

const ResultNotMin = "NOT_MIN"

ResultNotMin indicates that the given value is below the defined minimum.

const ResultNotMinLength = "NOT_MIN_LENGTH"

ResultNotMinLength indicates that the length of the given value is below the defined number.

const ResultNotSame = "NOT_SAME"

ResultNotSame indicates that the given two values are not equal to each other.

Functions

func FailIfNoPanic

func FailIfNoPanic(t *testing.T)

FailIfNoPanic fails if test didn't panic. Use this function with the defer.

func Register

func Register(name string, maker MakeFunc)

Register registers the given checker name and the maker function.

Types

type CheckFunc

type CheckFunc func(value, parent reflect.Value) Result

CheckFunc defines the checker function.

func MakeRegexpChecker

func MakeRegexpChecker(expression string, invalidResult Result) CheckFunc

MakeRegexpChecker makes a regexp checker for the given regexp expression with the given invalid result.

type MakeFunc

type MakeFunc func(params string) CheckFunc

MakeFunc defines the maker function.

func MakeRegexpMaker

func MakeRegexpMaker(expression string, invalidResult Result) MakeFunc

MakeRegexpMaker makes a regexp checker maker for the given regexp expression with the given invalid result.

type Mistakes

type Mistakes map[string]Result

Mistakes provides mapping to checker result for the invalid fields.

func Check

func Check(s interface{}) (Mistakes, bool)

Check checks the given struct based on the checkers listed in each field's strcut tag named checkers.

type Result

type Result string

Result is a unique textual identifier for the mistake.

const ResultRequired Result = "REQUIRED"

ResultRequired indicates that the required value is missing.

const ResultValid Result = "VALID"

ResultValid result indicates that the user input is valid.

func IsASCII

func IsASCII(value string) Result

IsASCII checks if the given string consists of only ASCII characters.

func IsAlphanumeric

func IsAlphanumeric(value string) Result

IsAlphanumeric checks if the given string consists of only alphanumeric characters.

func IsAmexCreditCard

func IsAmexCreditCard(number string) Result

IsAmexCreditCard checks if the given valie is a valid AMEX credit card.

func IsAnyCreditCard

func IsAnyCreditCard(number string) Result

IsAnyCreditCard checks if the given value is a valid credit card number.

func IsCidr

func IsCidr(value string) Result

IsCidr checker checks if the value is a valid CIDR notation IP address and prefix length.

func IsDigits

func IsDigits(value string) Result

IsDigits checks if the given string consists of only digit characters.

func IsDinersCreditCard

func IsDinersCreditCard(number string) Result

IsDinersCreditCard checks if the given valie is a valid Diners credit card.

func IsDiscoveryCreditCard

func IsDiscoveryCreditCard(number string) Result

IsDiscoveryCreditCard checks if the given valie is a valid Discovery credit card.

func IsEmail

func IsEmail(email string) Result

IsEmail checks if the given string is an email address.

func IsFqdn

func IsFqdn(domain string) Result

IsFqdn checks if the given string is a fully qualified domain name.

func IsIP

func IsIP(value string) Result

IsIP checks if the given value is an IP address.

func IsIPV4

func IsIPV4(value string) Result

IsIPV4 checks if the given value is an IPv4 address.

func IsIPV6

func IsIPV6(value string) Result

IsIPV6 checks if the given value is an IPv6 address.

func IsJcbCreditCard

func IsJcbCreditCard(number string) Result

IsJcbCreditCard checks if the given valie is a valid JCB 15 credit card.

func IsLuhn

func IsLuhn(number string) Result

IsLuhn checks if the given number is valid based on the Luhn algorithm.

func IsMac

func IsMac(value string) Result

IsMac checks if the given value is a valid an IEEE 802 MAC-48, EUI-48, EUI-64, or a 20-octet IP over InfiniBand link-layer address.

func IsMasterCardCreditCard

func IsMasterCardCreditCard(number string) Result

IsMasterCardCreditCard checks if the given valie is a valid MasterCard credit card.

func IsMax

func IsMax(value interface{}, max float64) Result

IsMax checks if the given value is below than the given maximum.

func IsMaxLength

func IsMaxLength(value interface{}, maxLength int) Result

IsMaxLength checks if the length of the given value is less than the given maximum length.

func IsMin

func IsMin(value interface{}, min float64) Result

IsMin checks if the given value is above than the given minimum.

func IsMinLength

func IsMinLength(value interface{}, minLength int) Result

IsMinLength checks if the length of the given value is greather than the given minimum length.

func IsRequired

func IsRequired(v interface{}) Result

IsRequired checks if the given required value is present.

func IsUnionPayCreditCard

func IsUnionPayCreditCard(number string) Result

IsUnionPayCreditCard checks if the given valie is a valid UnionPay credit card.

func IsVisaCreditCard

func IsVisaCreditCard(number string) Result

IsVisaCreditCard checks if the given valie is a valid Visa credit card.