fix: ignore fields of json:"-"

Author: tsuzu

pkg/analysis/commentstart/testdata/src/a/a.go

@@ -5,6 +5,8 @@ type CommentStartTestStruct struct {
 	EmptyJSONTag  string `json:""`
 	InlineJSONTag string `json:",inline"`
 	NoComment     string `json:"noComment"` // want "field NoComment is missing godoc comment"
+	Ignored       string `json:"-"`
+	Hyphen        string `json:"-,"` // want "field Hyphen is missing godoc comment"
 
 	// IncorrectStartComment is a field with an incorrect start to the comment. // want "godoc for field IncorrectStartComment should start with 'incorrectStartComment ...'"
 	IncorrectStartComment string `json:"incorrectStartComment"`

pkg/analysis/commentstart/testdata/src/a/a.go.golden

@@ -5,6 +5,8 @@ type CommentStartTestStruct struct {
 	EmptyJSONTag  string `json:""`
 	InlineJSONTag string `json:",inline"`
 	NoComment     string `json:"noComment"` // want "field NoComment is missing godoc comment"
+	Ignored       string `json:"-"`
+	Hyphen        string `json:"-,"` // want "field Hyphen is missing godoc comment"
 
 	// incorrectStartComment is a field with an incorrect start to the comment. // want "godoc for field IncorrectStartComment should start with 'incorrectStartComment ...'"
 	IncorrectStartComment string `json:"incorrectStartComment"`

pkg/analysis/helpers/extractjsontags/analyzer.go

@@ -81,6 +81,7 @@ func run(pass *analysis.Pass) (interface{}, error) {
 	return results, nil
 }
 
+//nolint:cyclop
 func extractTagInfo(tag *ast.BasicLit) FieldTagInfo {
 	if tag == nil || tag.Value == "" {
 		return FieldTagInfo{Missing: true}
@@ -106,6 +107,15 @@ func extractTagInfo(tag *ast.BasicLit) FieldTagInfo {
 
 	tagValues := strings.Split(tagValue, ",")
 
+	if len(tagValues) == 1 && tagValues[0] == "-" {
+		return FieldTagInfo{
+			Ignored:  true,
+			RawValue: tagValue,
+			Pos:      pos,
+			End:      end,
+		}
+	}
+
 	if len(tagValues) == 2 && tagValues[0] == "" && tagValues[1] == "inline" {
 		return FieldTagInfo{
 			Inline:   true,
@@ -132,6 +142,9 @@ type FieldTagInfo struct {
 	// Name is the name of the field extracted from the json tag.
 	Name string
 
+	// Ignored is true if the field is ignored by json package.
+	Ignored bool
+
 	// OmitEmpty is true if the field has the omitempty option in the json tag.
 	OmitEmpty bool