Omit empty <properties> tag when there are no properties.

Go doesn't omit empty parent tags for empty values[1], so we'll work
around this for now by creating a pointer to the property slice.

[1]: https://github.com/golang/go/issues/7233.

go-junit-report_test.go

@@ -223,21 +223,26 @@ func testReport(input, reportFile, packageName string, t *testing.T) {
 func modifyForBackwardsCompat(testsuites junit.Testsuites) junit.Testsuites {
 	testsuites.XMLName.Local = ""
 	for i, suite := range testsuites.Suites {
-		if covIdx, covProp := getProperty("coverage.statements.pct", suite.Properties); covIdx > -1 {
-			pct, _ := strconv.ParseFloat(covProp.Value, 64)
-			testsuites.Suites[i].Properties[covIdx].Value = fmt.Sprintf("%.2f", pct)
-		}
-		testsuites.Suites[i].Properties = dropProperty("go.version", suite.Properties)
-
 		for j := range suite.Testcases {
 			testsuites.Suites[i].Testcases[j].Classname = suite.Name
 		}
+
+		if suite.Properties != nil {
+			if covIdx, covProp := getProperty("coverage.statements.pct", *suite.Properties); covIdx > -1 {
+				pct, _ := strconv.ParseFloat(covProp.Value, 64)
+				(*testsuites.Suites[i].Properties)[covIdx].Value = fmt.Sprintf("%.2f", pct)
+			}
+			testsuites.Suites[i].Properties = dropProperty("go.version", suite.Properties)
+		}
 	}
 	return testsuites
 }
 
 func dropNewProperties(testsuites junit.Testsuites) junit.Testsuites {
 	for i, suite := range testsuites.Suites {
+		if suite.Properties == nil {
+			continue
+		}
 		ps := suite.Properties
 		ps = dropProperty("goos", ps)
 		ps = dropProperty("goarch", ps)
@@ -247,14 +252,20 @@ func dropNewProperties(testsuites junit.Testsuites) junit.Testsuites {
 	return testsuites
 }
 
-func dropProperty(name string, properties []junit.Property) []junit.Property {
+func dropProperty(name string, properties *[]junit.Property) *[]junit.Property {
+	if properties == nil {
+		return nil
+	}
 	var props []junit.Property
-	for _, prop := range properties {
+	for _, prop := range *properties {
 		if prop.Name != name {
 			props = append(props, prop)
 		}
 	}
-	return props
+	if len(props) == 0 {
+		return nil
+	}
+	return &props
 }
 
 func getProperty(name string, properties []junit.Property) (int, junit.Property) {

pkg/junit/junit.go

@@ -48,7 +48,7 @@ type Testsuite struct {
 	Time      string `xml:"time,attr"`                // duration in seconds
 	Timestamp string `xml:"timestamp,attr,omitempty"` // date and time in ISO8601
 
-	Properties []Property `xml:"properties>property,omitempty"`
+	Properties *[]Property `xml:"properties>property,omitempty"`
 	Testcases  []Testcase  `xml:"testcase,omitempty"`
 	SystemOut  *Output     `xml:"system-out,omitempty"`
 	SystemErr  *Output     `xml:"system-err,omitempty"`
@@ -56,7 +56,13 @@ type Testsuite struct {
 
 // AddProperty adds a property with the given name and value to this Testsuite.
 func (t *Testsuite) AddProperty(name, value string) {
-	t.Properties = append(t.Properties, Property{Name: name, Value: value})
+	prop := Property{Name: name, Value: value}
+	if t.Properties == nil {
+		t.Properties = &[]Property{prop}
+		return
+	}
+	props := append(*t.Properties, prop)
+	t.Properties = &props
 }
 
 // AddTestcase adds Testcase tc to this Testsuite.

pkg/junit/junit_test.go

@@ -27,7 +27,7 @@ func TestMarshalUnmarshal(t *testing.T) {
 				Skipped:    1,
 				Time:       "12.345",
 				Timestamp:  "2012-03-09T14:38:06+01:00",
-				Properties: []Property{{"key", "value"}},
+				Properties: properties("key", "value"),
 				Testcases: []Testcase{
 					{
 						Name:      "test1",
@@ -62,3 +62,14 @@ func TestMarshalUnmarshal(t *testing.T) {
 		t.Errorf("Unmarshal result incorrect, diff (-want +got):\n%s\n", diff)
 	}
 }
+
+func properties(keyvals ...string) *[]Property {
+	if len(keyvals)%2 != 0 {
+		panic("invalid keyvals specified")
+	}
+	var props []Property
+	for i := 0; i < len(keyvals); i += 2 {
+		props = append(props, Property{keyvals[i], keyvals[i+1]})
+	}
+	return &props
+}