feature: struct-tag warns on (useless) options on ignored fields (#1487)

rule/struct_tag.go

@@ -180,6 +180,10 @@ func (w lintStructTagRule) checkTaggedField(checkCtx *checkContext, f *ast.Field
 			w.addFailureWithTagKey(f.Tag, msg, tag.Key)
 		}
 
+		if msg, ok := checkOptionsOnIgnoredField(tag); !ok {
+			w.addFailureWithTagKey(f.Tag, msg, tag.Key)
+		}
+
 		checker, ok := w.tagCheckers[tagKey(tag.Key)]
 		if !ok {
 			continue // we don't have a checker for the tag
@@ -561,13 +565,6 @@ func checkYAMLTag(checkCtx *checkContext, tag *structtag.Tag, _ ast.Expr) (messa
 }
 
 func checkSpannerTag(checkCtx *checkContext, tag *structtag.Tag, _ ast.Expr) (message string, succeeded bool) {
-	if tag.Name == "-" {
-		if len(tag.Options) > 0 {
-			return fmt.Sprintf("useless option(s) %s for ignored field", strings.Join(tag.Options, ",")), false
-		}
-		return "", true
-	}
-
 	for _, opt := range tag.Options {
 		if !checkCtx.isUserDefined(keySpanner, opt) {
 			return fmt.Sprintf(msgUnknownOption, opt), false
@@ -577,6 +574,28 @@ func checkSpannerTag(checkCtx *checkContext, tag *structtag.Tag, _ ast.Expr) (me
 	return "", true
 }
 
+// checkOptionsOnIgnoredField checks if an ignored struct field (tag name "-") has any options specified.
+// It returns a message and false if there are useless options present, or an empty message and true if valid.
+func checkOptionsOnIgnoredField(tag *structtag.Tag) (message string, succeeded bool) {
+	if tag.Name != "-" {
+		return "", true
+	}
+
+	switch len(tag.Options) {
+	case 0:
+		return "", true
+	case 1:
+		opt := strings.TrimSpace(tag.Options[0])
+		if opt == "" {
+			return "", true // accept "-," as options
+		}
+
+		return fmt.Sprintf("useless option %s for ignored field", opt), false
+	default:
+		return fmt.Sprintf("useless options %s for ignored field", strings.Join(tag.Options, ",")), false
+	}
+}
+
 func checkValidateOptionsAlternatives(checkCtx *checkContext, alternatives []string) (message string, succeeded bool) {
 	for _, alternative := range alternatives {
 		alternative := strings.TrimSpace(alternative)

testdata/struct_tag.go

@@ -192,7 +192,7 @@ type PropertiesTags struct {
 type SpannerUser struct {
 	ID        int       `spanner:"user_id"`
 	Name      string    `spanner:"full_name"`
-	Email     string    `spanner:"-"`                    // Valid: ignore field
+	Email     string    `spanner:"-"` // Valid: ignore field
 	CreatedAt time.Time `spanner:"created_at"`
-	UpdatedAt time.Time `spanner:"updated_at,unknown"`   // MATCH /unknown option "unknown" in spanner tag/
+	UpdatedAt time.Time `spanner:"updated_at,unknown"` // MATCH /unknown option "unknown" in spanner tag/
-}
+}

testdata/struct_tag_user_options.go

@@ -1,5 +1,7 @@
 package fixtures
 
+import "time"
+
 type RangeAllocation struct {
 	metav1.TypeMeta   `json:",inline"`
 	metav1.ObjectMeta `json:"metadata,omitempty"`
@@ -49,6 +51,49 @@ type TomlUser struct {
 
 type SpannerUserOptions struct {
 	ID   int    `spanner:"user_id,mySpannerOption"`
-	A    int    `spanner:"-,mySpannerOption"`       // MATCH /useless option(s) mySpannerOption for ignored field in spanner tag/
+	A    int    `spanner:"-,mySpannerOption"`       // MATCH /useless option mySpannerOption for ignored field in spanner tag/
 	Name string `spanner:"full_name,unknownOption"` // MATCH /unknown option "unknownOption" in spanner tag/
 }
+
+type uselessOptions struct {
+	A  int       `bson:"-,"`
+	B  int       `bson:"-,omitempty"`           // MATCH /useless option omitempty for ignored field in bson tag/
+	C  int       `bson:"-,omitempty,omitempty"` // MATCH /useless options omitempty,omitempty for ignored field in bson tag/
+	D  int       `datastore:"-,"`
+	E  int       `datastore:"-,omitempty"`           // MATCH /useless option omitempty for ignored field in datastore tag/
+	F  int       `datastore:"-,omitempty,omitempty"` // MATCH /useless options omitempty,omitempty for ignored field in datastore tag/
+	G  int       `json:"-,"`
+	H  int       `json:"-,omitempty"`           // MATCH /useless option omitempty for ignored field in json tag/
+	I  int       `json:"-,omitempty,omitempty"` // MATCH /useless options omitempty,omitempty for ignored field in json tag/
+	J  int       `mapstructure:"-,"`
+	K  int       `mapstructure:"-,squash"`              // MATCH /useless option squash for ignored field in mapstructure tag/
+	L  int       `mapstructure:"-,omitempty,omitempty"` // MATCH /useless options omitempty,omitempty for ignored field in mapstructure tag/
+	M  int       `properties:"-,"`
+	N  int       `properties:"-,default=15"`                           // MATCH /useless option default=15 for ignored field in properties tag/
+	O  time.Time `properties:"-,layout=2006-01-02,default=2006-01-02"` // MATCH /useless options layout=2006-01-02,default=2006-01-02 for ignored field in properties tag/
+	P  int       `spanner:"-,"`
+	Q  int       `spanner:"-,mySpannerOption"`                 // MATCH /useless option mySpannerOption for ignored field in spanner tag/
+	R  int       `spanner:"-,mySpannerOption,mySpannerOption"` // MATCH /useless options mySpannerOption,mySpannerOption for ignored field in spanner tag/
+	S  int       `toml:"-,"`
+	T  int       `toml:"-,omitempty"`           // MATCH /useless option omitempty for ignored field in toml tag/
+	U  int       `toml:"-,omitempty,omitempty"` // MATCH /useless options omitempty,omitempty for ignored field in toml tag/
+	V  int       `url:"-,"`
+	W  int       `url:"-,omitempty"`           // MATCH /useless option omitempty for ignored field in url tag/
+	X  int       `url:"-,omitempty,omitempty"` // MATCH /useless options omitempty,omitempty for ignored field in url tag/
+	Y  int       `xml:"-,"`
+	Z  int       `xml:"-,omitempty"`           // MATCH /useless option omitempty for ignored field in xml tag/
+	Aa int       `xml:"-,omitempty,omitempty"` // MATCH /useless options omitempty,omitempty for ignored field in xml tag/
+	Ba int       `yaml:"-,"`
+	Ca int       `yaml:"-,omitempty"`           // MATCH /useless option omitempty for ignored field in yaml tag/
+	Da int       `yaml:"-,omitempty,omitempty"` // MATCH /useless options omitempty,omitempty for ignored field in yaml tag/
+
+	// MATCH:59 /unknown option "" in bson tag/
+	// MATCH:62 /unknown option "" in datastore tag/
+	// MATCH:68 /unknown option "" in mapstructure tag/
+	// MATCH:71 /unknown or malformed option "" in properties tag/
+	// MATCH:74 /unknown option "" in spanner tag/
+	// MATCH:77 /unknown option "" in toml tag/
+	// MATCH:80 /unknown option "" in url tag/
+	// MATCH:83 /unknown option "" in xml tag/
+	// MATCH:86 /unknown option "" in yaml tag/
+}