Add test for compatibility on legacy logging overrides

logging/mirai-logging-log4j2/test/MiraiLog4JAdapterTest.kt

@@ -21,6 +21,17 @@ import kotlin.test.assertIs
 
 internal class MiraiLog4JAdapterTest {
 
+    @Suppress("DEPRECATION")
+    @Test
+    fun `services prevail than legacy overrides`() {
+        MiraiLogger.setDefaultLoggerCreator {
+            net.mamoe.mirai.utils.SimpleLogger("my logger") { _: String?, _: Throwable? -> }
+        }
+
+        @Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
+        assertIs<net.mamoe.mirai.internal.utils.Log4jLoggerAdapter>(MiraiLogger.Factory.create(this::class))
+    }
+
     @Test
     fun `using log4j`() {
         assertIs<MiraiLog4JFactory>(loadService(MiraiLogger.Factory::class))

mirai-core-api/src/commonTest/kotlin/logging/LoggingCompatibilityTest.kt

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2019-2021 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/dev/LICENSE
+ */
+
+package net.mamoe.mirai.logging
+
+import net.mamoe.mirai.utils.MiraiLogger
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertIs
+
+internal class LoggingCompatibilityTest {
+
+    @Suppress("DEPRECATION")
+    @Test
+    fun `legacy overrides are still working if no services are found`() {
+        val messages = StringBuilder()
+
+        MiraiLogger.setDefaultLoggerCreator {
+            net.mamoe.mirai.utils.SimpleLogger("my logger") { message: String?, _: Throwable? ->
+                messages.append(message)
+            }
+        }
+
+        val created = MiraiLogger.Factory.create(this::class)
+        assertIs<MiraiLogger>(created)
+        created.info("test")
+
+        assertEquals("test", messages.toString().trim())
+    }
+}