Valigo - Simple Validation Library for Go

A flexible and easy-to-use validation framework for Go that supports strings, integers, floats, and time values through a clean pipeline pattern.

✨ Features

• Simple API - Build validations with small, composable actions
• Pipeline Pattern - Chain multiple checks in a single pipe
• Type Support - String, int, float64, and time.Time validators
• Schema Validation - Validate multiple fields together
• Custom Validators - Define your own rules per type
• Custom Error Messages - Use ErrMsg("...") with {VALUE} placeholder
• Parse + Validate - Decode JSON and validate in one step
• Structured Errors - PipeError, ValidationErrors, and ParseError

📦 Installation

go get github.com/mrbns/valgo

🚀 Quick Start

package main

import (
	"fmt"

	"github.com/mrbns/valgo/lib/v"
)

func main() {
	pipe := v.StringPipe("user@example.com", v.NotEmpty(), v.IsEmail())

	if err := pipe.Validate(); err != nil {
		fmt.Println("Validation failed:", err)
		return
	}

	fmt.Println("Email is valid!")
}

📖 Basic Concepts

Pipe

A pipe validates one value by running actions in order.

Action

An action is a single rule (for example, IsEmail() or Min(18)).

Schema

A schema groups multiple pipes and validates a struct or payload.

💡 Usage Examples

Validate a Single String

pipe := v.StringPipe(
	"test@example.com",
	v.NotEmpty(),
	v.IsEmail(),
	v.MaxLength(50),
)

if err := pipe.Validate(); err != nil {
	fmt.Println(err)
}

Validate a Number

pipe := v.IntPipe(
	25,
	v.Min(18),
	v.Max(100),
	v.IsPositive(),
)

if err := pipe.Validate(); err != nil {
	fmt.Println(err)
}

Validate a Float

pipe := v.FloatPipe(
	99.99,
	v.MinFloat(0.0),
	v.MaxFloat(1000.0),
)

if err := pipe.Validate(); err != nil {
	fmt.Println(err)
}

Validate Time

pipe := v.TimePipe(
	time.Now().Add(-2*time.Hour),
	v.BeforeNow(),
	v.IsWeekday(),
)

if err := pipe.Validate(); err != nil {
	fmt.Println(err)
}

Validate Multiple Fields (Schema)

schema := v.NewPipesMap(v.PipeMap{
	"email": v.StringPipe("user@example.com", v.NotEmpty(), v.IsEmail()),
	"age":   v.IntPipe(25, v.Min(18)),
	"price": v.FloatPipe(19.99, v.MinFloat(0)),
})

// Stop at first error
if err := schema.Validate(); err != nil {
	fmt.Println(err)
}

// Return all field errors
if err := schema.ValidateAll(); err != nil {
	if errs, ok := err.(v.ValidationErrors); ok {
		for _, fieldErr := range errs {
			fmt.Printf("%s: %v\n", fieldErr.Key, fieldErr.Err)
		}
	}
}

Build Schema with Entries

schema := v.NewPipesBuilder(
	v.Entry("email").StringPipe("user@example.com", v.NotEmpty(), v.IsEmail()),
	v.Entry("age").IntPipe(20, v.Min(18)),
)

Parse JSON and Validate in One Step

type UserSchema struct {
	v.Include
	Name string `json:"name"`
	Age  int    `json:"age"`
}

func (u *UserSchema) Rules() (v.PipeSet, error) {
	return v.NewPipesMap(v.PipeMap{
		"name": v.StringPipe(u.Name, v.NotEmpty(), v.MaxLength(40)),
		"age":  v.IntPipe(u.Age, v.NonZero(), v.Min(18)),
	}), nil
}

func parseAndValidate(data []byte) error {
	var payload UserSchema
	return v.ParseBytesFull(data, &payload)
}

Custom Error Messages

pipe := v.IntPipe(
	15,
	v.Min(18, v.ErrMsg("You must be at least 18, but got {VALUE}")),
	v.Max(65, v.ErrMsg("{VALUE} exceeds maximum age of 65")),
)

Custom Validators

nameRule := v.CustomString(func(value string) bool {
	return strings.HasPrefix(value, "user_")
}, v.ErrMsg("username must start with user_"))

evenRule := v.CustomNumber(func(value int) bool {
	return value%2 == 0
}, v.ErrMsg("{VALUE} must be an even number"))

_ = v.StringPipe("user_john", nameRule)
_ = v.IntPipe(10, evenRule)

Custom Pipe

pipe := v.CustomPipe("secret", func(value string) error {
	if value == "" {
		return errors.New("cannot be empty")
	}
	return nil
})

schema := v.NewPipesMap(v.PipeMap{"token": pipe})

⚠️ Error Types

• *v.PipeError - Single field validation error (key + error)
• v.ValidationErrors - Multiple field errors from ValidateAll()
• *v.ParseError - Parse/Rules/Validation lifecycle errors from Parse helpers

All error types support errors.Is / errors.As through Unwrap.

📋 Available String Validators

Validator	Description
NotEmpty()	String must not be empty
Enum([]string)	Value must be one of allowed values
Pattern(regex)	Value must match regex
MinLength(n)	Minimum length
MaxLength(n)	Maximum length
HasPrefix(prefix)	Must start with prefix
HasSuffix(suffix)	Must end with suffix
EqualFold(target)	Case-insensitive equality
Contains(substr)	Must contain substring
CustomString(fn)	Custom string validator
IsAlpha()	Letters only
IsAlphaNumeric()	Letters and numbers only
IsAscii()	ASCII only
IsBase32()	Base32 format
IsBase58()	Base58 format
IsBase64()	Base64 format
IsBitcoinAddress()	Bitcoin address
IsCreditCard()	Credit card number
IsDate()	Date string
IsDataURI()	Data URI format
IsDecimal()	Decimal number string
IsEmail()	Email format
IsEvmAddress()	Ethereum address
IsHTML()	HTML content
IsHexColor()	Hex color format
IsHexDecimal()	Hexadecimal format
IsHSL()	HSL color format
IsIPV4()	IPv4 address
IsIPV6()	IPv6 address
IsJSON()	JSON string
IsRGB()	RGB/RGBA format
IsULID()	ULID format
IsURL()	URL format
IsUUID()	UUID (any supported version)
IsUUIDV1()	UUID v1
IsUUIDV3()	UUID v3
IsUUIDV4()	UUID v4
IsUUIDV5()	UUID v5
IsValidPath()	Filesystem path
IsValidPort()	Network port (0-65535)
IsXML()	XML string
IsANSIC()	ANSI C date/time format
IsUnixDate()	UnixDate format
IsRubyDate()	RubyDate format
IsRFC822()	RFC822 date format
IsRFC822Z()	RFC822Z date format
IsRFC850()	RFC850 date format
IsRFC1123()	RFC1123 date format
IsRFC1123Z()	RFC1123Z date format
IsRFC3339()	RFC3339 date format
IsRFC3339Nano()	RFC3339Nano date format
IsKitchen()	Kitchen time format
IsStamp()	Stamp format
IsStampMilli()	StampMilli format
IsStampMicro()	StampMicro format
IsStampNano()	StampNano format
IsDateTime()	DateTime format
IsTimeOnly()	TimeOnly format

🔢 Available Integer Validators

Validator	Description
CustomNumber(fn)	Custom int validator
Min(n)	Value must be >= n
Max(n)	Value must be <= n
Gt(n)	Value must be > n
Gte(n)	Value must be >= n
Lt(n)	Value must be < n
Lte(n)	Value must be <= n
IsPositive()	Value must be > 0
IsNegative()	Value must be < 0
NonZero()	Value must be != 0
IsIntString()	Placeholder validator (currently always true)

📊 Available Float Validators

Validator	Description
CustomFloat(fn)	Custom float validator
MinFloat(n)	Value must be >= n
MaxFloat(n)	Value must be <= n
GtFloat(n)	Value must be > n
GteFloat(n)	Value must be >= n
LtFloat(n)	Value must be < n
LteFloat(n)	Value must be <= n
IsPositiveFloat()	Value must be >= 0
IsNegativeFloat()	Value must be < 0

🕒 Available Time Validators

Validator	Description
CustomTime(fn)	Custom time validator
Before(t)	Must be before t
After(t)	Must be after t
Between(start, end)	Must be strictly between start and end
BeforeNow()	Must be in the past
AfterNow()	Must be in the future
NotEmptyDate()	Must not be zero time.Time
SameDay(t)	Same year/month/day as t
SameMonth(t)	Same year/month as t
SameYear(t)	Same year as t
MinDate(t)	Must be on or after t
MaxDate(t)	Must be on or before t
Equal(t)	Must equal t
NotEqual(t)	Must not equal t
OldOfDays(n)	Must be at least n days old
OldOf(d)	Must be at least duration d old
NewOf(n)	Must be at least n days in the future
SameWeek(t)	Same ISO week as t
IsWeekday()	Must be Monday-Friday
IsTimezone()	Must have timezone offset in valid range

🧠 Validation Helpers

• v.Validate(schema) - Validate schema and stop at first error
• v.ValidateAll(schema) - Validate schema and return all errors
• v.ValidateAllParallel(schema) - Current behavior matches ValidateAll (sequential)

📝 Notes

• Validate() stops on the first failed action in each pipe.
• ValidateAll() collects all failed fields and returns v.ValidationErrors.
• PipeMap iteration order is Go map iteration order.

🤝 Contributing

Contributions are welcome! Feel free to open issues or submit pull requests.

📚 Source Reference

For more detailed information about each validator, check:

• lib/v/string_actions.go - String validators
• lib/v/int_actions.go - Integer validators
• lib/v/float_actions.go - Float validators
• lib/v/time_actions.go - Time validators
• lib/v/parser.go - Parse and schema validation flow
• lib/v/errors.go - Error types
• lib/is/string.go - Low-level validation functions

📝 License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

author

Mr Binary Sniper. @mrbns.