feature: add support for TOML struct tags in struct-tag rule (#1255)

rule/struct_tag.go

@@ -106,6 +106,7 @@ const (
 	keyMapstructure = "mapstructure"
 	keyProtobuf     = "protobuf"
 	keyRequired     = "required"
+	keyTOML         = "toml"
 	keyURL          = "url"
 	keyValidate     = "validate"
 	keyXML          = "xml"
@@ -212,6 +213,11 @@ func (w lintStructTagRule) checkTaggedField(f *ast.Field) {
 			if tag.Name != "true" && tag.Name != "false" {
 				w.addFailure(f.Tag, "required should be 'true' or 'false'")
 			}
+		case keyTOML:
+			msg, ok := w.checkTOMLTag(tag.Options)
+			if !ok {
+				w.addFailure(f.Tag, msg)
+			}
 		case keyURL:
 			msg, ok := w.checkURLTag(tag.Options)
 			if !ok {
@@ -435,6 +441,21 @@ func (w lintStructTagRule) checkValidateTag(options []string) (string, bool) {
 	return "", true
 }
 
+func (w lintStructTagRule) checkTOMLTag(options []string) (string, bool) {
+	for _, opt := range options {
+		switch opt {
+		case "omitempty":
+		default:
+			if w.isUserDefined(keyTOML, opt) {
+				continue
+			}
+			return fmt.Sprintf("unknown option '%s' in TOML tag", opt), false
+		}
+	}
+
+	return "", true
+}
+
 func (w lintStructTagRule) checkValidateOptionsAlternatives(alternatives []string) (string, bool) {
 	for _, alternative := range alternatives {
 		alternative := strings.TrimSpace(alternative)

test/struct_tag_test.go

@@ -20,6 +20,7 @@ func TestStructTagWithUserOptions(t *testing.T) {
 			"datastore,myDatastoreOption",
 			"mapstructure,myMapstructureOption",
 			"validate,displayName",
+			"toml,unknown",
 		},
 	})
 }

testdata/struct_tag.go

@@ -158,3 +158,8 @@ type ValidateUser struct {
 	BadComplex2 string `validate:"gt=0,dive,eq=1|eq=2,endkeys,required"`              // MATCH /option 'endkeys' without a previous 'keys' option in validate tag/
 	BadComplex3 string `validate:"gt=0,dive,keys,eq=1|eq=2,endkeys,endkeys,required"` // MATCH /option 'endkeys' without a previous 'keys' option in validate tag/
 }
+
+type TomlUser struct {
+	Username string `toml:"username,omitempty"`
+	Location string `toml:"location,unknown"` // MATCH /unknown option 'unknown' in TOML tag/
+}

testdata/struct_tag_user_options.go

@@ -41,3 +41,8 @@ type ValidateUser struct {
 	BadComplex2 string `validate:"gt=0,dive,eq=1|eq=2,endkeys,required"`              // MATCH /option 'endkeys' without a previous 'keys' option in validate tag/
 	BadComplex3 string `validate:"gt=0,dive,keys,eq=1|eq=2,endkeys,endkeys,required"` // MATCH /option 'endkeys' without a previous 'keys' option in validate tag/
 }
+
+type TomlUser struct {
+	Username string `toml:"username,omitempty"`
+	Location string `toml:"location,unknown"`
+}