fix(marshal): omit fields tagged with "-"

This is a behavior of json.Marshal() that should be emulated

internal/path/path.go

@@ -5,16 +5,20 @@ import (
 	"strings"
 )
 
-const omitEmptyToken string = "omitempty"
+const (
+	omitEmptyToken  string = "omitempty"
+	omitAlwaysToken string = "-"
+)
 
 type Segment struct {
 	Name string
 	List bool
 }
 
 type Path struct {
-	segments  []Segment
-	OmitEmpty bool
+	segments   []Segment
+	OmitEmpty  bool
+	OmitAlways bool
 }
 
 func (p Path) Len() int {
@@ -44,11 +48,12 @@ func ComputePath(field reflect.StructField) Path {
 	var segments []Segment
 	name := field.Name
 	omitempty := false
+	omitalways := false
 
 	if tag := field.Tag.Get("json"); tag != "" {
-		name, omitempty = parseTag(tag, field.Name)
+		name, omitempty, omitalways = parseTag(tag, field.Name)
 	} else if tag := field.Tag.Get("jsonry"); tag != "" {
-		name, omitempty = parseTag(tag, field.Name)
+		name, omitempty, omitalways = parseTag(tag, field.Name)
 		segments = parseSegments(name)
 	}
 
@@ -60,12 +65,17 @@ func ComputePath(field reflect.StructField) Path {
 	}
 
 	return Path{
-		OmitEmpty: omitempty,
-		segments:  segments,
+		OmitEmpty:  omitempty,
+		OmitAlways: omitalways,
+		segments:   segments,
 	}
 }
 
-func parseTag(tag, defaultName string) (name string, omitempty bool) {
+func parseTag(tag, defaultName string) (name string, omitempty, omitalways bool) {
+	if tag == omitAlwaysToken {
+		return defaultName, false, true
+	}
+
 	parts := strings.Split(tag, ",")
 
 	if len(parts) >= 1 && len(parts[0]) > 0 {

internal/path/path_test.go

@@ -51,4 +51,26 @@ var _ = Describe("Path", func() {
 			Expect(p.OmitEmpty).To(BeTrue())
 		})
 	})
+
+	Context("always omit", func() {
+		It("picks it up from a JSON tag", func() {
+			p := path.ComputePath(reflect.StructField{Tag: `json:"-"`})
+			Expect(p.OmitAlways).To(BeTrue())
+		})
+
+		It("picks it up from a JSONry tag", func() {
+			p := path.ComputePath(reflect.StructField{Tag: `jsonry:"-"`})
+			Expect(p.OmitAlways).To(BeTrue())
+		})
+
+		It("allows a literal name `-` from a JSON tag", func() {
+			p := path.ComputePath(reflect.StructField{Tag: `json:"-,"`})
+			Expect(p.OmitAlways).To(BeFalse())
+		})
+
+		It("allows a literal name `-` from a JSONry tag", func() {
+			p := path.ComputePath(reflect.StructField{Tag: `jsonry:"-,"`})
+			Expect(p.OmitAlways).To(BeFalse())
+		})
+	})
 })

marshal.go

@@ -44,7 +44,9 @@ func marshalStruct(ctx context.Context, in reflect.Value) (map[string]interface{
 
 		if public(f) {
 			p := path.ComputePath(f)
-			if !p.OmitEmpty || !in.Field(i).IsZero() {
+			shouldSkip := p.OmitAlways || (p.OmitEmpty && in.Field(i).IsZero())
+
+			if !shouldSkip {
 				r, err := marshal(ctx.WithField(f.Name, f.Type), in.Field(i))
 				if err != nil {
 					return nil, err

marshal_test.go

@@ -256,6 +256,22 @@ var _ = Describe("Marshal", func() {
 		})
 	})
 
+	Describe("omitting struct fields", func() {
+		It("omits struct fields tagged with `-`", func() {
+			type s struct {
+				A string `jsonry:"-"`
+			}
+			expectToMarshal(s{A: "foo"}, `{}`)
+		})
+
+		It("allows literal field name `-` ", func() {
+			type s struct {
+				A string `jsonry:"-,"`
+			}
+			expectToMarshal(s{A: "foo"}, `{"-":"foo"}`)
+		})
+	})
+
 	Describe("inputs", func() {
 		It("accept a struct", func() {
 			var s struct{}