💯Go Struct and Field validation, including Cross Field, Cross Struct, Map, Slice and Array diving
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validator/validator.go

484 lines
13 KiB

/**
* Package validator
*
* MISC:
* - anonymous structs - they don't have names so expect the Struct name within StructErrors to be blank
*
*/
package validator
import (
"bytes"
"errors"
"fmt"
"reflect"
"strings"
"sync"
"time"
"unicode"
)
const (
utf8HexComma = "0x2C"
utf8Pipe = "0x7C"
tagSeparator = ","
orSeparator = "|"
tagKeySeparator = "="
structOnlyTag = "structonly"
omitempty = "omitempty"
skipValidationTag = "-"
diveTag = "dive"
fieldErrMsg = "Key: \"%s\" Error:Field validation for \"%s\" failed on the \"%s\" tag"
arrayIndexFieldName = "%s[%d]"
mapIndexFieldName = "%s[%v]"
invalidValidation = "Invalid validation tag on field %s"
undefinedValidation = "Undefined validation function on field %s"
)
var (
timeType = reflect.TypeOf(time.Time{})
timePtrType = reflect.TypeOf(&time.Time{})
errsPool = &sync.Pool{New: newValidationErrors}
tagsCache = &tagCacheMap{m: map[string][]*tagCache{}}
)
// returns new ValidationErrors to the pool
func newValidationErrors() interface{} {
return map[string]*FieldError{}
}
type tagCache struct {
tagVals [][]string
isOrVal bool
}
type tagCacheMap struct {
lock sync.RWMutex
m map[string][]*tagCache
}
func (s *tagCacheMap) Get(key string) ([]*tagCache, bool) {
s.lock.RLock()
defer s.lock.RUnlock()
value, ok := s.m[key]
return value, ok
}
func (s *tagCacheMap) Set(key string, value []*tagCache) {
s.lock.Lock()
defer s.lock.Unlock()
s.m[key] = value
}
// Validate contains the validator settings passed in using the Config struct
type Validate struct {
config Config
}
// Config contains the options that a Validator instance will use.
// It is passed to the New() function
type Config struct {
TagName string
ValidationFuncs map[string]Func
}
// Func accepts all values needed for file and cross field validation
// topStruct = top level struct when validating by struct otherwise nil
// currentStruct = current level struct when validating by struct otherwise optional comparison value
// field = field value for validation
// param = parameter used in validation i.e. gt=0 param would be 0
type Func func(topStruct reflect.Value, currentStruct reflect.Value, field reflect.Value, fieldtype reflect.Type, fieldKind reflect.Kind, param string) bool
// ValidationErrors is a type of map[string]*FieldError
// it exists to allow for multiple errors to be passed from this library
// and yet still subscribe to the error interface
type ValidationErrors map[string]*FieldError
// Error is intended for use in development + debugging and not intended to be a production error message.
// It allows ValidationErrors to subscribe to the Error interface.
// All information to create an error message specific to your application is contained within
// the FieldError found within the ValidationErrors map
func (ve ValidationErrors) Error() string {
buff := bytes.NewBufferString("")
for key, err := range ve {
buff.WriteString(fmt.Sprintf(fieldErrMsg, key, err.Field, err.Tag))
buff.WriteString("\n")
}
return strings.TrimSpace(buff.String())
}
// FieldError contains a single field's validation error along
// with other properties that may be needed for error message creation
type FieldError struct {
Field string
Tag string
Kind reflect.Kind
Type reflect.Type
Param string
Value interface{}
}
// New creates a new Validate instance for use.
func New(config Config) *Validate {
return &Validate{config: config}
}
// RegisterValidation adds a validation Func to a Validate's map of validators denoted by the key
// NOTE: if the key already exists, the previous validation function will be replaced.
// NOTE: this method is not thread-safe
func (v *Validate) RegisterValidation(key string, f Func) error {
if len(key) == 0 {
return errors.New("Function Key cannot be empty")
}
if f == nil {
return errors.New("Function cannot be empty")
}
v.config.ValidationFuncs[key] = f
return nil
}
// Field validates a single field using tag style validation and returns ValidationErrors
// NOTE: it returns ValidationErrors instead of a single FieldError because this can also
// validate Array, Slice and maps fields which may contain more than one error
func (v *Validate) Field(field interface{}, tag string) ValidationErrors {
errs := errsPool.Get().(map[string]*FieldError)
fieldVal := reflect.ValueOf(field)
v.traverseField(fieldVal, fieldVal, fieldVal, "", errs, false, tag, "")
if len(errs) == 0 {
errsPool.Put(errs)
return nil
}
return errs
}
// FieldWithValue validates a single field, against another fields value using tag style validation and returns ValidationErrors
// NOTE: it returns ValidationErrors instead of a single FieldError because this can also
// validate Array, Slice and maps fields which may contain more than one error
func (v *Validate) FieldWithValue(val interface{}, field interface{}, tag string) ValidationErrors {
errs := errsPool.Get().(map[string]*FieldError)
topVal := reflect.ValueOf(val)
v.traverseField(topVal, topVal, reflect.ValueOf(field), "", errs, false, tag, "")
if len(errs) == 0 {
errsPool.Put(errs)
return nil
}
return errs
}
// Struct validates a structs exposed fields, and automatically validates nested structs, unless otherwise specified.
func (v *Validate) Struct(current interface{}) ValidationErrors {
errs := errsPool.Get().(map[string]*FieldError)
sv := reflect.ValueOf(current)
v.tranverseStruct(sv, sv, sv, "", errs, true)
if len(errs) == 0 {
errsPool.Put(errs)
return nil
}
return errs
}
// tranverseStruct traverses a structs fields and then passes them to be validated by traverseField
func (v *Validate) tranverseStruct(topStruct reflect.Value, currentStruct reflect.Value, current reflect.Value, errPrefix string, errs ValidationErrors, useStructName bool) {
if current.Kind() == reflect.Ptr && !current.IsNil() {
current = current.Elem()
}
if current.Kind() != reflect.Struct && current.Kind() != reflect.Interface {
panic("value passed for validation is not a struct")
}
typ := current.Type()
if useStructName {
errPrefix += typ.Name() + "."
}
numFields := current.NumField()
var fld reflect.StructField
for i := 0; i < numFields; i++ {
fld = typ.Field(i)
if !unicode.IsUpper(rune(fld.Name[0])) {
continue
}
v.traverseField(topStruct, currentStruct, current.Field(i), errPrefix, errs, true, fld.Tag.Get(v.config.TagName), fld.Name)
}
}
// traverseField validates any field, be it a struct or single field, ensures it's validity and passes it along to be validated via it's tag options
func (v *Validate) traverseField(topStruct reflect.Value, currentStruct reflect.Value, current reflect.Value, errPrefix string, errs ValidationErrors, isStructField bool, tag string, name string) {
if tag == skipValidationTag {
return
}
kind := current.Kind()
if kind == reflect.Ptr && !current.IsNil() {
current = current.Elem()
kind = current.Kind()
}
typ := current.Type()
// this also allows for tags 'required' and 'omitempty' to be used on
// nested struct fields because when len(tags) > 0 below and the value is nil
// then required failes and we check for omitempty just before that
if (kind == reflect.Ptr || kind == reflect.Interface) && current.IsNil() {
if strings.Contains(tag, omitempty) {
return
}
tags := strings.Split(tag, tagSeparator)
if len(tags) > 0 {
var param string
vals := strings.SplitN(tags[0], tagKeySeparator, 2)
if len(vals) > 1 {
param = vals[1]
}
errs[errPrefix+name] = &FieldError{
Field: name,
Tag: vals[0],
Param: param,
Value: current.Interface(),
Kind: kind,
Type: typ,
}
return
}
}
switch kind {
case reflect.Struct, reflect.Interface:
if kind == reflect.Interface {
current = current.Elem()
kind = current.Kind()
if kind == reflect.Ptr && !current.IsNil() {
current = current.Elem()
kind = current.Kind()
}
// changed current, so have to get inner type again
typ = current.Type()
if kind != reflect.Struct {
goto FALLTHROUGH
}
}
if typ != timeType && typ != timePtrType {
if kind == reflect.Struct {
// required passed validationa above so stop here
// if only validating the structs existance.
if strings.Contains(tag, structOnlyTag) {
return
}
v.tranverseStruct(topStruct, current, current, errPrefix+name+".", errs, false)
return
}
}
FALLTHROUGH:
fallthrough
default:
if len(tag) == 0 {
return
}
}
tags, isCached := tagsCache.Get(tag)
if !isCached {
tags = []*tagCache{}
for _, t := range strings.Split(tag, tagSeparator) {
if t == diveTag {
tags = append(tags, &tagCache{tagVals: [][]string{[]string{t}}})
break
}
// if a pipe character is needed within the param you must use the utf8Pipe representation "0x7C"
orVals := strings.Split(t, orSeparator)
cTag := &tagCache{isOrVal: len(orVals) > 1, tagVals: make([][]string, len(orVals))}
tags = append(tags, cTag)
var key string
var param string
for i, val := range orVals {
vals := strings.SplitN(val, tagKeySeparator, 2)
key = vals[0]
if len(key) == 0 {
panic(strings.TrimSpace(fmt.Sprintf(invalidValidation, name)))
}
if len(vals) > 1 {
param = strings.Replace(strings.Replace(vals[1], utf8HexComma, ",", -1), utf8Pipe, "|", -1)
}
cTag.tagVals[i] = []string{key, param}
}
}
tagsCache.Set(tag, tags)
}
var dive bool
var diveSubTag string
for _, cTag := range tags {
if cTag.tagVals[0][0] == diveTag {
dive = true
diveSubTag = strings.TrimLeft(strings.SplitN(tag, diveTag, 2)[1], ",")
break
}
if cTag.tagVals[0][0] == omitempty {
if !hasValue(topStruct, currentStruct, current, typ, kind, "") {
return
}
continue
}
if v.validateField(topStruct, currentStruct, current, typ, kind, errPrefix, errs, cTag, name) {
return
}
}
if dive {
// traverse slice or map here
// or panic ;)
switch kind {
case reflect.Slice, reflect.Array:
v.traverseSlice(topStruct, currentStruct, current, errPrefix, errs, diveSubTag, name)
case reflect.Map:
v.traverseMap(topStruct, currentStruct, current, errPrefix, errs, diveSubTag, name)
default:
// throw error, if not a slice or map then should not have gotten here
// bad dive tag
panic("dive error! can't dive on a non slice or map")
}
}
}
// traverseSlice traverses a Slice or Array's elements and passes them to traverseField for validation
func (v *Validate) traverseSlice(topStruct reflect.Value, currentStruct reflect.Value, current reflect.Value, errPrefix string, errs ValidationErrors, tag string, name string) {
for i := 0; i < current.Len(); i++ {
idxField := current.Index(i)
if idxField.Kind() == reflect.Ptr && !idxField.IsNil() {
idxField = idxField.Elem()
}
v.traverseField(topStruct, currentStruct, idxField, errPrefix, errs, false, tag, fmt.Sprintf(arrayIndexFieldName, name, i))
}
}
// traverseMap traverses a map's elements and passes them to traverseField for validation
func (v *Validate) traverseMap(topStruct reflect.Value, currentStruct reflect.Value, current reflect.Value, errPrefix string, errs ValidationErrors, tag string, name string) {
for _, key := range current.MapKeys() {
idxField := current.MapIndex(key)
if idxField.Kind() == reflect.Ptr && !idxField.IsNil() {
idxField = idxField.Elem()
}
v.traverseField(topStruct, currentStruct, idxField, errPrefix, errs, false, tag, fmt.Sprintf(mapIndexFieldName, name, key.Interface()))
}
}
// validateField validates a field based on the provided tag's key and param values and returns true if there is an error or false if all ok
func (v *Validate) validateField(topStruct reflect.Value, currentStruct reflect.Value, current reflect.Value, currentType reflect.Type, currentKind reflect.Kind, errPrefix string, errs ValidationErrors, cTag *tagCache, name string) bool {
if cTag.isOrVal {
errTag := ""
for _, val := range cTag.tagVals {
valFunc, ok := v.config.ValidationFuncs[val[0]]
if !ok {
panic(strings.TrimSpace(fmt.Sprintf(undefinedValidation, name)))
}
if valFunc(topStruct, currentStruct, current, currentType, currentKind, val[1]) {
return false
}
errTag += orSeparator + val[0]
}
errs[errPrefix+name] = &FieldError{
Field: name,
Tag: errTag[1:],
Value: current.Interface(),
Type: currentType,
Kind: currentKind,
}
return true
}
valFunc, ok := v.config.ValidationFuncs[cTag.tagVals[0][0]]
if !ok {
panic(strings.TrimSpace(fmt.Sprintf(undefinedValidation, name)))
}
if valFunc(topStruct, currentStruct, current, currentType, currentKind, cTag.tagVals[0][1]) {
return false
}
errs[errPrefix+name] = &FieldError{
Field: name,
Tag: cTag.tagVals[0][0],
Value: current.Interface(),
Param: cTag.tagVals[0][1],
Type: currentType,
Kind: currentKind,
}
return true
}