Add file path validation

baked_in.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"net"
 	"net/url"
+	"os"
 	"reflect"
 	"strconv"
 	"strings"
@@ -97,6 +98,7 @@ var (
 		"email":            isEmail,
 		"url":              isURL,
 		"uri":              isURI,
+		"file":             isFile,
 		"base64":           isBase64,
 		"base64url":        isBase64URL,
 		"contains":         contains,
@@ -1060,6 +1062,23 @@ func isURL(fl FieldLevel) bool {
 	panic(fmt.Sprintf("Bad field type %T", field.Interface()))
 }
 
+// IsFile is the validation function for validating if the current field's value is a valid file path.
+func isFile(fl FieldLevel) bool {
+	field := fl.Field()
+
+	switch field.Kind() {
+	case reflect.String:
+		fileInfo, err := os.Stat(field.String())
+		if err != nil {
+			return false
+		}
+
+		return !fileInfo.IsDir()
+	}
+
+	panic(fmt.Sprintf("Bad field type %T", field.Interface()))
+}
+
 // IsEmail is the validation function for validating if the current field's value is a valid email address.
 func isEmail(fl FieldLevel) bool {
 	return emailRegex.MatchString(fl.Field().String())

testdata/a.go

@@ -0,0 +1 @@
+package testdata

validator_test.go

@@ -8,6 +8,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
+	"path/filepath"
 	"reflect"
 	"strings"
 	"testing"
@@ -4446,6 +4447,39 @@ func TestBase64URLValidation(t *testing.T) {
 	}
 }
 
+func TestFileValidation(t *testing.T) {
+	validate := New()
+
+	tests := []struct {
+		title    string
+		param    string
+		expected bool
+	}{
+		{"empty path", "", false},
+		{"regular file", filepath.Join("testdata", "a.go"), true},
+		{"missing file", filepath.Join("testdata", "no.go"), false},
+		{"directory, not a file", "testdata", false},
+	}
+
+	for _, test := range tests {
+		errs := validate.Var(test.param, "file")
+
+		if test.expected {
+			if !IsEqual(errs, nil) {
+				t.Fatalf("Test: '%s' failed Error: %s", test.title, errs)
+			}
+		} else {
+			if IsEqual(errs, nil) {
+				t.Fatalf("Test: '%s' failed Error: %s", test.title, errs)
+			}
+		}
+	}
+
+	PanicMatches(t, func() {
+		validate.Var(6, "file")
+	}, "Bad field type int")
+}
+
 func TestEthereumAddressValidation(t *testing.T) {
 
 	validate := New()