feature: add support for properties tag in struct-tag rule (#1289)

Author: chavacava

RULES_DESCRIPTIONS.md

@@ -924,7 +924,7 @@ _Configuration_: N/A
 ## struct-tag
 
 _Description_: Struct tags are not checked at compile time.
-This rule spots errors in struct tags of the following types: asn1, bson, datastore, default, json, mapstructure, protobuf, required, toml, url, validate, xml, yaml.
+This rule spots errors in struct tags of the following types: asn1, bson, datastore, default, json, mapstructure, properties, protobuf, required, toml, url, validate, xml, yaml.
 
 _Configuration_: (optional) list of user defined options.
 

rule/struct_tag.go

@@ -105,6 +105,7 @@ const (
 	keyDefault      = "default"
 	keyJSON         = "json"
 	keyMapstructure = "mapstructure"
+	keyProperties   = "properties"
 	keyProtobuf     = "protobuf"
 	keyRequired     = "required"
 	keyTOML         = "toml"
@@ -205,6 +206,11 @@ func (w lintStructTagRule) checkTaggedField(f *ast.Field) {
 			if !ok {
 				w.addFailure(f.Tag, msg)
 			}
+		case keyProperties:
+			msg, ok := w.checkPropertiesTag(f.Type, tag.Options)
+			if !ok {
+				w.addFailure(f.Tag, msg)
+			}
 		case keyProtobuf:
 			msg, ok := w.checkProtobufTag(tag)
 			if !ok {
@@ -506,6 +512,43 @@ func (lintStructTagRule) typeValueMatch(t ast.Expr, val string) bool {
 
 	return typeMatches
 }
+func (w lintStructTagRule) checkPropertiesTag(t ast.Expr, options []string) (string, bool) {
+	if len(options) == 0 {
+		return "", true
+	}
+
+	hasDefault := false
+	for _, opt := range options {
+		key, val, found := strings.Cut(opt, "=")
+		switch key {
+		case "default":
+			if hasDefault {
+				return "properties tag accepts only one default option", false
+			}
+			hasDefault = true
+
+			if !found {
+				return "malformed default for properties tag", false
+			}
+
+			if !w.typeValueMatch(t, val) {
+				return "field type and default value type mismatch in properties tag", false
+			}
+		case "layout":
+			if !found || strings.TrimSpace(val) == "" {
+				return "malformed layout option for properties tag", false
+			}
+
+			if gofmt(t) != "time.Time" {
+				return "layout option is only applicable to fields of type time.Time in properties tag", false
+			}
+		default:
+			return fmt.Sprintf("unknown option %q in properties tag", opt), false
+		}
+	}
+
+	return "", true
+}
 
 func (w lintStructTagRule) checkProtobufTag(tag *structtag.Tag) (string, bool) {
 	// check name

testdata/struct_tag.go

@@ -163,3 +163,19 @@ type TomlUser struct {
 	Username string `toml:"username,omitempty"`
 	Location string `toml:"location,unknown"` // MATCH /unknown option 'unknown' in TOML tag/
 }
+
+type PropertiesTags struct {
+	Field int               `properties:"-"`
+	Field int               `properties:"myName"`
+	Field int               `properties:"myName,default=15"`
+	Field int               `properties:"myName,default=sString"` // MATCH /field type and default value type mismatch in properties tag/
+	Field int               `properties:",default:15"`            // MATCH /unknown option "default:15" in properties tag/
+	Field int               `properties:",default=15,default=2"`  // MATCH /properties tag accepts only one default option/
+	Field time.Time         `properties:"date,layout=2006-01-02"`
+	Field time.Time         `properties:",layout=2006-01-02"`
+	Field time.Time         `properties:"date,layout"`            // MATCH /malformed layout option for properties tag/
+	Field time.Time         `properties:"date,layout=  "`         // MATCH /malformed layout option for properties tag/
+	Field string            `properties:"date,layout=2006-01-02"` // MATCH /layout option is only applicable to fields of type time.Time in properties tag/
+	Field []string          `properties:",default=a;b;c"`
+	Field map[string]string `properties:"myName,omitempty"` // MATCH /unknown option "omitempty" in properties tag/
+}