Add ParseAndValidate method

Signed-off-by: Knut Ahlers <knut@ahlers.me>

config.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/spf13/pflag"
+	validator "gopkg.in/validator.v2"
 )
 
 var (
@@ -45,6 +46,15 @@ func Parse(config interface{}) error {
 	return parse(config, nil)
 }
 
+// ParseAndValidate works exactly like Parse but implements an additional run of
+// the go-validator package on the configuration struct. Therefore additonal struct
+// tags are supported like described in the readme file of the go-validator package:
+//
+// https://github.com/go-validator/validator/tree/v2#usage
+func ParseAndValidate(config interface{}) error {
+	return parseAndValidate(config, nil)
+}
+
 // Args returns the non-flag command-line arguments.
 func Args() []string {
 	return fs.Args()
@@ -65,6 +75,14 @@ func SetVariableDefaults(defaults map[string]string) {
 	variableDefaults = defaults
 }
 
+func parseAndValidate(in interface{}, args []string) error {
+	if err := parse(in, args); err != nil {
+		return err
+	}
+
+	return validator.Validate(in)
+}
+
 func parse(in interface{}, args []string) error {
 	if args == nil {
 		args = os.Args

general_test.go

@@ -15,6 +15,10 @@ var _ = Describe("Testing general parsing", func() {
 		SadFlag     string
 	}
 
+	type tValidated struct {
+		Test string `flag:"test" default:"" validate:"nonzero"`
+	}
+
 	var (
 		err  error
 		args []string
@@ -106,4 +110,19 @@ var _ = Describe("Testing general parsing", func() {
 		})
 	})
 
+	Context("making use of the validator package", func() {
+		var cfgValidated tValidated
+
+		BeforeEach(func() {
+			cfgValidated = tValidated{}
+			args = []string{}
+		})
+
+		JustBeforeEach(func() {
+			err = parseAndValidate(&cfgValidated, args)
+		})
+
+		It("should have errored", func() { Expect(err).To(HaveOccurred()) })
+	})
+
 })