Add omitnil modifier (#1187)

## Fixes Or Enhances

Related issue: #1186

**Make sure that you've checked the boxes below before you submit PR:**
- [x] Tests exist or have been written that cover this particular
change.

@go-playground/validator-maintainers

baked_in.go

@@ -51,6 +51,7 @@ var (
 		endKeysTag:        {},
 		structOnlyTag:     {},
 		omitempty:         {},
+		omitnil:           {},
 		skipValidationTag: {},
 		utf8HexComma:      {},
 		utf8Pipe:          {},

cache.go

@@ -20,6 +20,7 @@ const (
 	typeOr
 	typeKeys
 	typeEndKeys
+	typeOmitNil
 )
 
 const (
@@ -252,6 +253,10 @@ func (v *Validate) parseFieldTagsRecursive(tag string, fieldName string, alias s
 			current.typeof = typeOmitEmpty
 			continue
 
+		case omitnil:
+			current.typeof = typeOmitNil
+			continue
+
 		case structOnlyTag:
 			current.typeof = typeStructOnly
 			continue

doc.go

@@ -194,6 +194,13 @@ such as min or max won't run, but if a value is set validation will run.
 
 	Usage: omitempty
 
+# Omit Nil
+
+Allows to skip the validation if the value is nil (same as omitempty, but
+only for the nil-values).
+
+	Usage: omitnil
+
 # Dive
 
 This tells the validator to dive into a slice, array or map and validate that

validator.go

@@ -112,6 +112,10 @@ func (v *validate) traverseField(ctx context.Context, parent reflect.Value, curr
 			return
 		}
 
+		if ct.typeof == typeOmitNil && (kind != reflect.Invalid && current.IsNil()) {
+			return
+		}
+
 		if ct.hasTag {
 			if kind == reflect.Invalid {
 				v.str1 = string(append(ns, cf.altName...))
@@ -233,6 +237,26 @@ OUTER:
 			ct = ct.next
 			continue
 
+		case typeOmitNil:
+			v.slflParent = parent
+			v.flField = current
+			v.cf = cf
+			v.ct = ct
+
+			switch field := v.Field(); field.Kind() {
+			case reflect.Slice, reflect.Map, reflect.Ptr, reflect.Interface, reflect.Chan, reflect.Func:
+				if field.IsNil() {
+					return
+				}
+			default:
+				if v.fldIsPointer && field.Interface() == nil {
+					return
+				}
+			}
+
+			ct = ct.next
+			continue
+
 		case typeEndKeys:
 			return
 

validator_instance.go

@@ -22,6 +22,7 @@ const (
 	structOnlyTag         = "structonly"
 	noStructLevelTag      = "nostructlevel"
 	omitempty             = "omitempty"
+	omitnil               = "omitnil"
 	isdefault             = "isdefault"
 	requiredWithoutAllTag = "required_without_all"
 	requiredWithoutTag    = "required_without"

validator_test.go

@@ -13196,14 +13196,14 @@ func TestSpiceDBValueFormatValidation(t *testing.T) {
 		tag      string
 		expected bool
 	}{
-		//Must be an asterisk OR a string containing alphanumeric characters and a restricted set a special symbols: _ | / - = +
+		// Must be an asterisk OR a string containing alphanumeric characters and a restricted set a special symbols: _ | / - = +
 		{"*", "spicedb=id", true},
 		{`azAZ09_|/-=+`, "spicedb=id", true},
 		{`a*`, "spicedb=id", false},
 		{`/`, "spicedb=id", true},
 		{"*", "spicedb", true},
 
-		//Must begin and end with a lowercase letter, may also contain numbers and underscores between, min length 3, max length 64
+		// Must begin and end with a lowercase letter, may also contain numbers and underscores between, min length 3, max length 64
 		{"a", "spicedb=permission", false},
 		{"1", "spicedb=permission", false},
 		{"a1", "spicedb=permission", false},
@@ -13213,7 +13213,7 @@ func TestSpiceDBValueFormatValidation(t *testing.T) {
 		{"abcdefghijklmnopqrstuvwxyz_0123456789_abcdefghijklmnopqrstuvwxyz", "spicedb=permission", true},
 		{"abcdefghijklmnopqrstuvwxyz_01234_56789_abcdefghijklmnopqrstuvwxyz", "spicedb=permission", false},
 
-		//Object types follow the same rules as permissions for the type name plus an optional prefix up to 63 characters with a /
+		// Object types follow the same rules as permissions for the type name plus an optional prefix up to 63 characters with a /
 		{"a", "spicedb=type", false},
 		{"1", "spicedb=type", false},
 		{"a1", "spicedb=type", false},
@@ -13606,3 +13606,47 @@ func TestTimeRequired(t *testing.T) {
 	NotEqual(t, err, nil)
 	AssertError(t, err.(ValidationErrors), "TestTime.Time", "TestTime.Time", "Time", "Time", "required")
 }
+
+func TestOmitNilAndRequired(t *testing.T) {
+	type (
+		OmitEmpty struct {
+			Str    string  `validate:"omitempty,required,min=10"`
+			StrPtr *string `validate:"omitempty,required,min=10"`
+			Inner  *OmitEmpty
+		}
+		OmitNil struct {
+			Str    string  `validate:"omitnil,required,min=10"`
+			StrPtr *string `validate:"omitnil,required,min=10"`
+			Inner  *OmitNil
+		}
+	)
+
+	var (
+		validate = New(WithRequiredStructEnabled())
+		valid    = "this is the long string to pass the validation rule"
+	)
+
+	t.Run("compare using valid data", func(t *testing.T) {
+		err1 := validate.Struct(OmitEmpty{Str: valid, StrPtr: &valid, Inner: &OmitEmpty{Str: valid, StrPtr: &valid}})
+		err2 := validate.Struct(OmitNil{Str: valid, StrPtr: &valid, Inner: &OmitNil{Str: valid, StrPtr: &valid}})
+
+		Equal(t, err1, nil)
+		Equal(t, err2, nil)
+	})
+
+	t.Run("compare fully empty omitempty and omitnil", func(t *testing.T) {
+		err1 := validate.Struct(OmitEmpty{})
+		err2 := validate.Struct(OmitNil{})
+
+		Equal(t, err1, nil)
+		AssertError(t, err2, "OmitNil.Str", "OmitNil.Str", "Str", "Str", "required")
+	})
+
+	t.Run("validate in deep", func(t *testing.T) {
+		err1 := validate.Struct(OmitEmpty{Str: valid, Inner: &OmitEmpty{}})
+		err2 := validate.Struct(OmitNil{Str: valid, Inner: &OmitNil{}})
+
+		Equal(t, err1, nil)
+		AssertError(t, err2, "OmitNil.Inner.Str", "OmitNil.Inner.Str", "Str", "Str", "required")
+	})
+}