fix: handle JSON tags correctly

see issue pact-foundation#140

dsl/matcher.go

@@ -299,7 +299,11 @@ func match(srcType reflect.Type, params params) Matcher {
 
 		for i := 0; i < srcType.NumField(); i++ {
 			field := srcType.Field(i)
-			result[field.Tag.Get("json")] = match(field.Type, pluckParams(field.Type, field.Tag.Get("pact")))
+			fieldName := getJsonFieldName(field)
+			if fieldName == "" {
+				continue
+			}
+			result[fieldName] = match(field.Type, pluckParams(field.Type, field.Tag.Get("pact")))
 		}
 		return result
 	case reflect.String:
@@ -332,6 +336,24 @@ func match(srcType reflect.Type, params params) Matcher {
 	}
 }
 
+// getJsonFieldName retrieves the name for a JSON field as
+// https://golang.org/pkg/encoding/json/#Marshal would do.
+func getJsonFieldName(field reflect.StructField) string {
+	jsonTag := field.Tag.Get("json")
+	if jsonTag == "" {
+		return field.Name
+	}
+	// Field should be ignored according to the JSON marshal documentation.
+	if jsonTag == "-" {
+		return ""
+	}
+	commaIndex := strings.Index(jsonTag, ",")
+	if commaIndex > -1 {
+		return jsonTag[:commaIndex]
+	}
+	return jsonTag
+}
+
 // params are plucked from 'pact' struct tags as match() traverses
 // struct fields. They are passed back into match() along with their
 // associated type to serve as parameters for the dsl functions.

dsl/matcher_test.go

@@ -570,6 +570,20 @@ func TestMatch(t *testing.T) {
 		Integer int     `json:"integer" pact:"example=42"`
 		Float   float32 `json:"float" pact:"example=6.66"`
 	}
+	type jsonTagOmitemptyDTO struct {
+		Word string `json:"word,omitempty"`
+	}
+	type jsonTagMissingDTO struct {
+		Word string
+	}
+	type jsonTagIgnoreFieldDTO struct {
+		Word    string `json:"word"`
+		Ignored string `json:"-"`
+	}
+	type jsonTagDashDTO struct {
+		Word     string `json:"word"`
+		WordDash string `json:"-,"`
+	}
 	str := "str"
 	type args struct {
 		src interface{}
@@ -648,6 +662,43 @@ func TestMatch(t *testing.T) {
 				"float":   Like(float32(6.66)),
 			},
 		},
+		{
+			name: "recursive case - struct with json tag including omitempty",
+			args: args{
+				src: jsonTagOmitemptyDTO{},
+			},
+			want: StructMatcher{
+				"word": Like("string"),
+			},
+		},
+		{
+			name: "recursive case - struct without json tag",
+			args: args{
+				src: jsonTagMissingDTO{},
+			},
+			want: StructMatcher{
+				"Word": Like("string"),
+			},
+		},
+		{
+			name: "recursive case - struct with ignored field",
+			args: args{
+				src: jsonTagIgnoreFieldDTO{},
+			},
+			want: StructMatcher{
+				"word": Like("string"),
+			},
+		},
+		{
+			name: "recursive case - struct with field named '-'",
+			args: args{
+				src: jsonTagDashDTO{},
+			},
+			want: StructMatcher{
+				"word": Like("string"),
+				"-":    Like("string"),
+			},
+		},
 		{
 			name: "base case - string",
 			args: args{