Add required_if and required_unless

README.md

@@ -197,6 +197,8 @@ Baked-in Validations
 | min | Minimum |
 | oneof | One Of |
 | required | Required |
+| required_if | Required If |
+| required_unless | Required Unless |
 | required_with | Required With |
 | required_with_all | Required With All |
 | required_without | Required Without |

baked_in.go

@@ -64,6 +64,8 @@ var (
 	// or even disregard and use your own map if so desired.
 	bakedInValidators = map[string]Func{
 		"required":             hasValue,
+		"required_if":          requiredIf,
+		"required_unless":      requiredUnless,
 		"required_with":        requiredWith,
 		"required_with_all":    requiredWithAll,
 		"required_without":     requiredWithout,
@@ -1387,6 +1389,63 @@ func requireCheckFieldKind(fl FieldLevel, param string, defaultNotFoundValue boo
 	}
 }
 
+// requireCheckFieldValue is a func for check field value
+func requireCheckFieldValue(fl FieldLevel, param string, value string, defaultNotFoundValue bool) bool {
+	field, kind, _, found := fl.GetStructFieldOKAdvanced2(fl.Parent(), param)
+	if !found {
+		return defaultNotFoundValue
+	}
+
+	switch kind {
+
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return field.Int() == asInt(value)
+
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return field.Uint() == asUint(value)
+
+	case reflect.Float32, reflect.Float64:
+		return field.Float() == asFloat(value)
+
+	case reflect.Slice, reflect.Map, reflect.Array:
+		return int64(field.Len()) == asInt(value)
+	}
+
+	// default reflect.String:
+	return field.String() == value
+}
+
+// requiredIf is the validation function
+// The field under validation must be present and not empty only if all the other specified fields are equal to the value following with the specified field.
+func requiredIf(fl FieldLevel) bool {
+	params := parseOneOfParam2(fl.Param())
+	if len(params)%2 != 0 {
+		panic(fmt.Sprintf("Bad param number for required_if %s", fl.FieldName()))
+	}
+	for i := 0; i < len(params); i += 2 {
+		if !requireCheckFieldValue(fl, params[i], params[i+1], false) {
+			return true
+		}
+	}
+	return hasValue(fl)
+}
+
+// requiredUnless is the validation function
+// The field under validation must be present and not empty only unless all the other specified fields are equal to the value following with the specified field.
+func requiredUnless(fl FieldLevel) bool {
+	params := parseOneOfParam2(fl.Param())
+	if len(params)%2 != 0 {
+		panic(fmt.Sprintf("Bad param number for required_unless %s", fl.FieldName()))
+	}
+
+	for i := 0; i < len(params); i += 2 {
+		if requireCheckFieldValue(fl, params[i], params[i+1], false) {
+			return true
+		}
+	}
+	return hasValue(fl)
+}
+
 // ExcludedWith is the validation function
 // The field under validation must not be present or is empty if any of the other specified fields are present.
 func excludedWith(fl FieldLevel) bool {

doc.go

@@ -245,6 +245,40 @@ ensures the value is not nil.
 
 	Usage: required
 
+Required If
+
+The field under validation must be present and not empty only if all
+the other specified fields are equal to the value following the specified
+field. For strings ensures value is not "". For slices, maps, pointers,
+interfaces, channels and functions ensures the value is not nil.
+
+	Usage: required_if
+
+Examples:
+
+	// require the field if the Field1 is equal to the parameter given:
+	Usage: required_if=Field1 foobar
+
+	// require the field if the Field1 and Field2 is equal to the value respectively:
+	Usage: required_if=Field1 foo Field2 bar
+
+Required Unless
+
+The field under validation must be present and not empty unless all
+the other specified fields are equal to the value following the specified
+field. For strings ensures value is not "". For slices, maps, pointers,
+interfaces, channels and functions ensures the value is not nil.
+
+	Usage: required_unless
+
+Examples:
+
+	// require the field unless the Field1 is equal to the parameter given:
+	Usage: required_unless=Field1 foobar
+
+	// require the field unless the Field1 and Field2 is equal to the value respectively:
+	Usage: required_unless=Field1 foo Field2 bar
+
 Required With
 
 The field under validation must be present and not empty only if any

validator_instance.go

@@ -27,6 +27,8 @@ const (
 	requiredWithoutTag    = "required_without"
 	requiredWithTag       = "required_with"
 	requiredWithAllTag    = "required_with_all"
+	requiredIfTag         = "required_if"
+	requiredUnlessTag     = "required_unless"
 	skipValidationTag     = "-"
 	diveTag               = "dive"
 	keysTag               = "keys"
@@ -107,7 +109,7 @@ func New() *Validate {
 
 		switch k {
 		// these require that even if the value is nil that the validation should run, omitempty still overrides this behaviour
-		case requiredWithTag, requiredWithAllTag, requiredWithoutTag, requiredWithoutAllTag:
+		case requiredIfTag, requiredUnlessTag, requiredWithTag, requiredWithAllTag, requiredWithoutTag, requiredWithoutAllTag:
 			_ = v.registerValidation(k, wrapFunc(val), true, true)
 		default:
 			// no need to error check here, baked in will always be valid

validator_test.go

@@ -8695,6 +8695,151 @@ func TestEndsWithValidation(t *testing.T) {
 	}
 }
 
+func TestRequiredIf(t *testing.T) {
+	type Inner struct {
+		Field *string
+	}
+
+	fieldVal := "test"
+	test := struct {
+		Inner   *Inner
+		FieldE  string            `validate:"omitempty" json:"field_e"`
+		FieldER string            `validate:"required_if=FieldE test" json:"field_er"`
+		Field1  string            `validate:"omitempty" json:"field_1"`
+		Field2  *string           `validate:"required_if=Field1 test" json:"field_2"`
+		Field3  map[string]string `validate:"required_if=Field2 test" json:"field_3"`
+		Field4  interface{}       `validate:"required_if=Field3 1" json:"field_4"`
+		Field5  int               `validate:"required_if=Inner.Field test" json:"field_5"`
+		Field6  uint              `validate:"required_if=Field5 1" json:"field_6"`
+		Field7  float32           `validate:"required_if=Field6 1" json:"field_7"`
+		Field8  float64           `validate:"required_if=Field7 1.0" json:"field_8"`
+	}{
+		Inner:  &Inner{Field: &fieldVal},
+		Field2: &fieldVal,
+		Field3: map[string]string{"key": "val"},
+		Field4: "test",
+		Field5: 2,
+	}
+
+	validate := New()
+
+	errs := validate.Struct(test)
+	Equal(t, errs, nil)
+
+	test2 := struct {
+		Inner   *Inner
+		Inner2  *Inner
+		FieldE  string            `validate:"omitempty" json:"field_e"`
+		FieldER string            `validate:"required_if=FieldE test" json:"field_er"`
+		Field1  string            `validate:"omitempty" json:"field_1"`
+		Field2  *string           `validate:"required_if=Field1 test" json:"field_2"`
+		Field3  map[string]string `validate:"required_if=Field2 test" json:"field_3"`
+		Field4  interface{}       `validate:"required_if=Field2 test" json:"field_4"`
+		Field5  string            `validate:"required_if=Field3 1" json:"field_5"`
+		Field6  string            `validate:"required_if=Inner.Field test" json:"field_6"`
+		Field7  string            `validate:"required_if=Inner2.Field test" json:"field_7"`
+	}{
+		Inner:  &Inner{Field: &fieldVal},
+		Field2: &fieldVal,
+	}
+
+	errs = validate.Struct(test2)
+	NotEqual(t, errs, nil)
+
+	ve := errs.(ValidationErrors)
+	Equal(t, len(ve), 3)
+	AssertError(t, errs, "Field3", "Field3", "Field3", "Field3", "required_if")
+	AssertError(t, errs, "Field4", "Field4", "Field4", "Field4", "required_if")
+	AssertError(t, errs, "Field6", "Field6", "Field6", "Field6", "required_if")
+
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("test3 should have panicked!")
+		}
+	}()
+
+	test3 := struct {
+		Inner  *Inner
+		Field1 string `validate:"required_if=Inner.Field" json:"field_1"`
+	}{
+		Inner: &Inner{Field: &fieldVal},
+	}
+	_ = validate.Struct(test3)
+}
+
+func TestRequiredUnless(t *testing.T) {
+	type Inner struct {
+		Field *string
+	}
+
+	fieldVal := "test"
+	test := struct {
+		Inner   *Inner
+		FieldE  string            `validate:"omitempty" json:"field_e"`
+		FieldER string            `validate:"required_unless=FieldE test" json:"field_er"`
+		Field1  string            `validate:"omitempty" json:"field_1"`
+		Field2  *string           `validate:"required_unless=Field1 test" json:"field_2"`
+		Field3  map[string]string `validate:"required_unless=Field2 test" json:"field_3"`
+		Field4  interface{}       `validate:"required_unless=Field3 1" json:"field_4"`
+		Field5  int               `validate:"required_unless=Inner.Field test" json:"field_5"`
+		Field6  uint              `validate:"required_unless=Field5 2" json:"field_6"`
+		Field7  float32           `validate:"required_unless=Field6 0" json:"field_7"`
+		Field8  float64           `validate:"required_unless=Field7 0.0" json:"field_8"`
+	}{
+		FieldE: "test",
+		Field2: &fieldVal,
+		Field3: map[string]string{"key": "val"},
+		Field4: "test",
+		Field5: 2,
+	}
+
+	validate := New()
+
+	errs := validate.Struct(test)
+	Equal(t, errs, nil)
+
+	test2 := struct {
+		Inner   *Inner
+		Inner2  *Inner
+		FieldE  string            `validate:"omitempty" json:"field_e"`
+		FieldER string            `validate:"required_unless=FieldE test" json:"field_er"`
+		Field1  string            `validate:"omitempty" json:"field_1"`
+		Field2  *string           `validate:"required_unless=Field1 test" json:"field_2"`
+		Field3  map[string]string `validate:"required_unless=Field2 test" json:"field_3"`
+		Field4  interface{}       `validate:"required_unless=Field2 test" json:"field_4"`
+		Field5  string            `validate:"required_unless=Field3 0" json:"field_5"`
+		Field6  string            `validate:"required_unless=Inner.Field test" json:"field_6"`
+		Field7  string            `validate:"required_unless=Inner2.Field test" json:"field_7"`
+	}{
+		Inner:  &Inner{Field: &fieldVal},
+		FieldE: "test",
+		Field1: "test",
+	}
+
+	errs = validate.Struct(test2)
+	NotEqual(t, errs, nil)
+
+	ve := errs.(ValidationErrors)
+	Equal(t, len(ve), 3)
+	AssertError(t, errs, "Field3", "Field3", "Field3", "Field3", "required_unless")
+	AssertError(t, errs, "Field4", "Field4", "Field4", "Field4", "required_unless")
+	AssertError(t, errs, "Field7", "Field7", "Field7", "Field7", "required_unless")
+
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("test3 should have panicked!")
+		}
+	}()
+
+	test3 := struct {
+		Inner  *Inner
+		Field1 string `validate:"required_unless=Inner.Field" json:"field_1"`
+	}{
+		Inner: &Inner{Field: &fieldVal},
+	}
+	_ = validate.Struct(test3)
+}
+
 func TestRequiredWith(t *testing.T) {
 	type Inner struct {
 		Field *string