Serialize lists to empty list instead of null (#18)

Author: mduesterhoeft

router-protobuf/build.gradle.kts

@@ -24,6 +24,7 @@ dependencies {
     testImplementation("org.assertj:assertj-core:3.11.1")
     testImplementation("io.mockk:mockk:1.8.13.kotlin13")
     testImplementation("org.slf4j:slf4j-simple:1.7.26")
+    testImplementation("com.jayway.jsonpath:json-path:2.4.0")
 }
 
 

router-protobuf/src/main/kotlin/io/moia/router/proto/ProtoBufUtils.kt

@@ -34,13 +34,11 @@ object ProtoBufUtils {
         private fun removeWrapperObjects(json: ObjectNode): ObjectNode {
             val result = jacksonObjectMapper().createObjectNode()
             for (entry in json.fields()) {
-                if (entry.value.isContainerNode) {
+                if (entry.value.isContainerNode && entry.value.size() > 0) {
                     if (entry.value.size() > 0) {
                         result.set(entry.key,
                             removeWrapperObjects(entry.value)
                         )
-                    } else {
-                        result.set(entry.key, jacksonObjectMapper().nodeFactory.nullNode())
                     }
                 } else {
                     result.set(entry.key, entry.value)

router-protobuf/src/test/kotlin/io/moia/router/proto/ProtoBufUtilsTest.kt

@@ -0,0 +1,44 @@
+package io.moia.router.proto
+
+import com.google.protobuf.StringValue
+import com.jayway.jsonpath.JsonPath
+import io.moia.router.proto.sample.SampleOuterClass.ComplexSample
+import io.moia.router.proto.sample.SampleOuterClass.ComplexSample.SampleEnum.ONE
+import org.assertj.core.api.BDDAssertions.then
+import org.junit.jupiter.api.Test
+
+class ProtoBufUtilsTest {
+
+    @Test
+    fun `should serialize empty list`() {
+        val message = ComplexSample.newBuilder()
+            .addAllSamples(emptyList())
+            .build()
+
+        val json = ProtoBufUtils.toJsonWithoutWrappers(message)
+
+        then(JsonPath.read<List<Any>>(json, "samples")).isEmpty()
+    }
+
+    @Test
+    fun `should remove wrapper object`() {
+        val message = ComplexSample.newBuilder()
+            .setSomeString(StringValue.newBuilder().setValue("some").build())
+            .build()
+
+        val json = ProtoBufUtils.toJsonWithoutWrappers(message)
+
+        then(JsonPath.read<String>(json, "someString")).isEqualTo("some")
+    }
+
+    @Test
+    fun `should serialize value when it is the default`() {
+        val message = ComplexSample.newBuilder()
+            .setEnumAttribute(ONE) // enum zero value
+            .build()
+
+        val json = ProtoBufUtils.toJsonWithoutWrappers(message)
+
+        then(JsonPath.read<String>(json, "enumAttribute")).isEqualTo("ONE")
+    }
+}

router-protobuf/src/test/proto/Sample.proto

@@ -2,6 +2,8 @@ syntax = "proto3";
 
 package io.moia.router.proto.sample;
 
+import "google/protobuf/wrappers.proto";
+
 message Sample {
     string hello = 1;
     string request = 2;
@@ -16,4 +18,16 @@ message UnprocessableEntityError {
     string message = 1;
     string code = 2;
     string path = 3;
-}
+}
+
+message ComplexSample {
+    enum SampleEnum {
+        ONE = 0;
+        TWO = 1;
+    }
+
+    SampleEnum enumAttribute = 1;
+    repeated Sample samples = 2;
+    google.protobuf.StringValue someString = 3;
+}
+