Fix conversion helpers

Author: theunrepentantgeek

v2/pkg/genruntime/conversion_helpers.go

@@ -114,6 +114,13 @@ func GetFloatFromInt(i int) float64 {
 
 // ConvertJSONToString returns the string value of the given v1.JSON.
 func ConvertJSONToString(json v1.JSON) string {
+	// An empty v1.JSON marshals to the literal "null" (see (v1.JSON).MarshalJSON), but the value we want to
+	// round trip is the empty string. v1.JSON.UnmarshalJSON treats both "" and "null" as an empty Raw, so
+	// treating an empty Raw as the empty string here makes ConvertJSONToString(ConvertStringToJSON("")) lossless.
+	if len(json.Raw) == 0 {
+		return ""
+	}
+
 	// Ignoring error here, its always nil
 	marshalJSON, _ := json.MarshalJSON()
 	return string(marshalJSON)

v2/pkg/genruntime/conversion_helpers_test.go

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) Microsoft Corporation.
+ * Licensed under the MIT license.
+ */
+
+package genruntime_test
+
+import (
+	"testing"
+
+	. "github.com/onsi/gomega"
+	v1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
+
+	"github.com/Azure/azure-service-operator/v2/pkg/genruntime"
+)
+
+func TestConvertStringToJSON_RoundTripsThroughConvertJSONToString(t *testing.T) {
+	t.Parallel()
+
+	cases := map[string]struct {
+		value string
+	}{
+		"empty string": {
+			value: "",
+		},
+		"simple string": {
+			value: "value",
+		},
+		"numeric string": {
+			value: "123",
+		},
+		"boolean string": {
+			value: "true",
+		},
+		"json object string": {
+			value: `{"key":"value"}`,
+		},
+	}
+
+	for name, c := range cases {
+		name, c := name, c
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			g := NewGomegaWithT(t)
+
+			j := genruntime.ConvertStringToJSON(c.value)
+			actual := genruntime.ConvertJSONToString(j)
+			g.Expect(actual).To(Equal(c.value))
+		})
+	}
+}
+
+func TestConvertJSONToString_EmptyJSONReturnsEmptyString(t *testing.T) {
+	t.Parallel()
+	g := NewGomegaWithT(t)
+
+	g.Expect(genruntime.ConvertJSONToString(v1.JSON{})).To(Equal(""))
+}