From 49d1785b6d7677938cfbedcaf92cfb2c29b79ecc Mon Sep 17 00:00:00 2001
From: Mitchell Herrijgers <mitchellherrijgers@gmail.com>
Date: Tue, 22 Oct 2024 15:53:13 +0100
Subject: [PATCH] Support decorators with null fields of type

A customer experienced the following error:
```
Failed to connect to AxonIQ Console. Error: null cannot be cast to non-null type T of io.axoniq.console.framework.UtilsKt.unwrapPossiblyDecoratedClass$lambda-0. Will keep trying to connect
```

This is because a field of an expected decorated type is null.
The code in this PR adjusts the method to find the first suitable non-null field. If none is found, it will return the decorator itself.
---
 .../java/io/axoniq/console/framework/utils.kt | 17 +++--
 .../axoniq/console/framework/UtilsKtTest.kt   | 73 +++++++++++++++++++
 2 files changed, 82 insertions(+), 8 deletions(-)
 create mode 100644 console-framework-client/src/test/java/io/axoniq/console/framework/UtilsKtTest.kt

diff --git a/console-framework-client/src/main/java/io/axoniq/console/framework/utils.kt b/console-framework-client/src/main/java/io/axoniq/console/framework/utils.kt
index 86b08a0..5125578 100644
--- a/console-framework-client/src/main/java/io/axoniq/console/framework/utils.kt
+++ b/console-framework-client/src/main/java/io/axoniq/console/framework/utils.kt
@@ -26,18 +26,19 @@ import java.time.Duration
  * Useful for when users wrap components as decorators, like Axon FireStarter does.
  */
 fun <T : Any> T.unwrapPossiblyDecoratedClass(clazz: Class<out T>): T {
-    return fieldOfMatchingType(clazz)
-        ?.let { ReflectionUtils.getFieldValue(it, this) as T }
-        ?.unwrapPossiblyDecoratedClass(clazz)
-    // No field of provided type - reached end of decorator chain
-        ?: this
+    return fieldsOfMatchingType(clazz)
+            .mapNotNull { ReflectionUtils.getFieldValue(it, this) as T? }
+            .map { it.unwrapPossiblyDecoratedClass(clazz) }
+            .firstOrNull()
+            // No field of provided type - reached end of decorator chain
+            ?: this
 }
 
-private fun <T : Any> T.fieldOfMatchingType(clazz: Class<out T>): Field? {
+private fun <T : Any> T.fieldsOfMatchingType(clazz: Class<out T>): List<Field> {
     // When we reach our own AS-classes, stop unwrapping
-    if (this::class.java.name.startsWith("org.axonframework") && this::class.java.simpleName.startsWith("AxonServer")) return null
+    if (this::class.java.name.startsWith("org.axonframework") && this::class.java.simpleName.startsWith("AxonServer")) return listOf()
     return ReflectionUtils.fieldsOf(this::class.java)
-        .firstOrNull { f -> clazz.isAssignableFrom(f.type) }
+            .filter { f -> clazz.isAssignableFrom(f.type) }
 }
 
 fun <K, V> MutableMap<K, V>.computeIfAbsentWithRetry(key: K, retries: Int = 0, defaultValue: (K) -> V): V {
diff --git a/console-framework-client/src/test/java/io/axoniq/console/framework/UtilsKtTest.kt b/console-framework-client/src/test/java/io/axoniq/console/framework/UtilsKtTest.kt
new file mode 100644
index 0000000..d523157
--- /dev/null
+++ b/console-framework-client/src/test/java/io/axoniq/console/framework/UtilsKtTest.kt
@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2024. AxonIQ B.V.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.axoniq.console.framework
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class UtilsKtTest {
+    @Test
+    fun `Unwraps decorator with single field`() {
+        val core = MyCoreDecoratableService()
+        val decorated = MySingleValueDecoratableService(core)
+        val unwrapped = decorated.unwrapPossiblyDecoratedClass(MyDecoratableService::class.java)
+        assertEquals(core, unwrapped)
+    }
+
+    @Test
+    fun `Unwraps decorator that has a nullable field out of two`() {
+        val core = MyCoreDecoratableService()
+        val decorated = MyDoubleNullableValueDecoratableService(core, null)
+        val unwrapped = decorated.unwrapPossiblyDecoratedClass(MyDecoratableService::class.java)
+        val decorated2 = MyDoubleNullableValueDecoratableService(null, core)
+        val unwrapped2 = decorated2.unwrapPossiblyDecoratedClass(MyDecoratableService::class.java)
+        assertEquals(core, unwrapped)
+        assertEquals(core, unwrapped2)
+    }
+
+    @Test
+    fun `Does not crash on null fields of single-field decorator and returns decorator itself`() {
+        val decorated = MySingleValueDecoratableService(null)
+        val unwrapped = decorated.unwrapPossiblyDecoratedClass(MyDecoratableService::class.java)
+        assertEquals(decorated, unwrapped)
+    }
+
+    @Test
+    fun `Does not crash on both null fields of double-field decorator and returns decorator itself`() {
+        val decorated = MyDoubleNullableValueDecoratableService(null, null)
+        val unwrapped = decorated.unwrapPossiblyDecoratedClass(MyDecoratableService::class.java)
+        assertEquals(decorated, unwrapped)
+    }
+
+    interface MyDecoratableService {
+
+    }
+
+    class MyCoreDecoratableService : MyDecoratableService {
+
+    }
+
+    class MySingleValueDecoratableService(
+            val delegate: MyDecoratableService?
+    ) : MyDecoratableService
+
+
+    class MyDoubleNullableValueDecoratableService(
+            val delegate: MyDecoratableService?,
+            val delegate2: MyDecoratableService?,
+    ) : MyDecoratableService
+}
\ No newline at end of file