Add cron support

README.md

@@ -154,6 +154,7 @@ Baked-in Validations
 | btc_addr | Bitcoin Address |
 | btc_addr_bech32 | Bitcoin Bech32 Address (segwit) |
 | credit_card | Credit Card Number |
+| cron | Cron |
 | datetime | Datetime |
 | e164 | e164 formatted phone number |
 | email | E-mail String

baked_in.go

@@ -214,6 +214,7 @@ var (
 		"semver":                        isSemverFormat,
 		"dns_rfc1035_label":             isDnsRFC1035LabelFormat,
 		"credit_card":                   isCreditCard,
+		"cron":                          isCron,
 	}
 )
 
@@ -2524,3 +2525,9 @@ func isCreditCard(fl FieldLevel) bool {
 	}
 	return (sum % 10) == 0
 }
+
+// isCron is the validation function for validating if the current field's value is a valid cron expression
+func isCron(fl FieldLevel) bool {
+	cronString := fl.Field().String()
+	return cronRegex.MatchString(cronString)
+}

doc.go

@@ -1323,6 +1323,12 @@ This validates that a string value contains a valid credit card number using Luh
 
 	Usage: credit_card
 
+Cron
+
+This validates that a string value contains a valid cron expression.
+
+	Usage: cron
+
 Alias Validators and Tags
 
 NOTE: When returning an error, the tag returned in "FieldError" will be

regexes.go

@@ -64,6 +64,7 @@ const (
 	bicRegexString                   = `^[A-Za-z]{6}[A-Za-z0-9]{2}([A-Za-z0-9]{3})?$`
 	semverRegexString                = `^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$` // numbered capture groups https://semver.org/
 	dnsRegexStringRFC1035Label       = "^[a-z]([-a-z0-9]*[a-z0-9]){0,62}$"
+	cronRegexString                  = `(@(annually|yearly|monthly|weekly|daily|hourly|reboot))|(@every (\d+(ns|us|µs|ms|s|m|h))+)|((((\d+,)+\d+|(\d+(\/|-)\d+)|\d+|\*) ?){5,7})`
 )
 
 var (
@@ -128,4 +129,5 @@ var (
 	bicRegex                   = regexp.MustCompile(bicRegexString)
 	semverRegex                = regexp.MustCompile(semverRegexString)
 	dnsRegexRFC1035Label       = regexp.MustCompile(dnsRegexStringRFC1035Label)
+	cronRegex                  = regexp.MustCompile(cronRegexString)
 )

translations/en/en.go

@@ -1276,6 +1276,11 @@ func RegisterDefaultTranslations(v *validator.Validate, trans ut.Translator) (er
 			translation: "{0} must be a valid color",
 			override:    false,
 		},
+		{
+			tag:         "cron",
+			translation: "{0} must be a valid cron expression",
+			override:    false,
+		},
 		{
 			tag:         "oneof",
 			translation: "{0} must be one of [{1}]",

translations/it/it.go

@@ -124,7 +124,7 @@ func RegisterDefaultTranslations(v *validator.Validate, trans ut.Translator) (er
 		{
 			tag: "min",
 			customRegisFunc: func(ut ut.Translator) (err error) {
-        
+
 				if err = ut.Add("min-string", "{0} deve essere lungo almeno {1}", false); err != nil {
 					return
 				}
@@ -432,7 +432,7 @@ func RegisterDefaultTranslations(v *validator.Validate, trans ut.Translator) (er
 		{
 			tag: "lte",
 			customRegisFunc: func(ut ut.Translator) (err error) {
-        
+
 				if err = ut.Add("lte-string", "{0} deve essere lungo al massimo {1}", false); err != nil {
 					return
 				}
@@ -1132,6 +1132,11 @@ func RegisterDefaultTranslations(v *validator.Validate, trans ut.Translator) (er
 			translation: "{0} deve essere un colore valido",
 			override:    false,
 		},
+		{
+			tag:         "cron",
+			translation: "{0} deve essere una stringa cron valida",
+			override:    false,
+		},
 		{
 			tag:             "oneof",
 			translation:     "{0} deve essere uno di [{1}]",

validator_test.go

@@ -12323,3 +12323,37 @@ func TestMultiOrOperatorGroup(t *testing.T) {
 		}
 	}
 }
+
+func TestCronExpressionValidation(t *testing.T) {
+	tests := []struct {
+		value    string `validate:"cron"`
+		tag      string
+		expected bool
+	}{
+		{"0 0 12 * * ?", "cron", true},
+		{"0 15 10 ? * *", "cron", true},
+		{"0 15 10 * * ?", "cron", true},
+		{"0 15 10 * * ? 2005", "cron", true},
+		{"0 15 10 ? * 6L", "cron", true},
+		{"0 15 10 ? * 6L 2002-2005", "cron", true},
+		{"*/20 * * * *", "cron", true},
+		{"0 15 10 ? * MON-FRI", "cron", true},
+		{"0 15 10 ? * 6#3", "cron", true},
+		{"wrong", "cron", false},
+	}
+
+	validate := New()
+
+	for i, test := range tests {
+		errs := validate.Var(test.value, test.tag)
+		if test.expected {
+			if !IsEqual(errs, nil) {
+				t.Fatalf(`Index: %d cron "%s" failed Error: %s`, i, test.value, errs)
+			}
+		} else {
+			if IsEqual(errs, nil) {
+				t.Fatalf(`Index: %d cron "%s" should have errs`, i, test.value)
+			}
+		}
+	}
+}