toml-schema utilizes TOML to define validation schemas for input in a simple manner. Under the hood, we generate a map[string]interface{} rule definition that can be used by go-playground/validator.

It was created for use in the sabaresu serverless framework to enable configuration-based validation.

Schema are written in TOML, like so:

# key = "validators"
name = "string,required,min=1,max=128"
age = "number,required,int,min=1,max=150"
ecash = "number,required,min=0,max=150000"
is_cool = "boolean,required"

# A nested map can be added with [key]
[location]
address1 = "string,required"
address2 = "string,required"

# A slice is added with [[key]]

[[ships]]
id = "string,required,uuid"
make = "string,oneof=x-wing y-wing a-wing millenium falcon tie-fighter"

To validate data against your schema and constraints:

import (
    "github.com/Phamiliarize/toml-schema"
    "github.com/go-playground/validator/v10"
)

// Use any v10 instance of a go-playground/validator
// This allows you to extend the potential validators
v := schema.NewValidator(validator.New())
err := v.LoadSchema("mySchema", `test = "string,required"`)
if err != nil {
    panic(err)
}

// Returns a map[string]validation.ValidationErrors
err := v.ValidateSchema("mySchema", myData)
if err != nil {
    panic(err)
}

The supported constraints/validations are basically inline with go-playground/validator but since the end usecase is for JSON and Lua we require a "type constraint" on all fields.

Every field must start with a basic type. The basic types supported are: