perf(utils): 优化自动释放钩子的资源引用.

原本自动释放钩子对资源的引用, 可能会出现资源已经被关闭, 但仍然无法被 GC 回收的问题.
此次改动, 将会让钩子在关闭资源后, 将资源从列表中移除.
虽然, 自动释放钩子设计上仅会被 System.exit 动作触发, 但保险起见还是加上这个改动.

scalabot-app/src/main/kotlin/util/Utils.kt

@@ -81,17 +81,20 @@ private object UtilsInternal {
     val autoCloseableSet = mutableSetOf<AutoCloseable>()
 
     init {
-        Runtime.getRuntime().addShutdownHook(Thread({
-            log.debug { "Closing registered hook resources..." }
-            autoCloseableSet.forEach {
-                try {
-                    it.close()
-                } catch (e: Exception) {
-                    log.error(e) { "An exception occurred while closing the resource. (Resource: `$it`)" }
-                }
+        Runtime.getRuntime().addShutdownHook(Thread(this::doCloseResources, "Shutdown-AutoCloseable"))
+    }
+
+    fun doCloseResources() {
+        log.debug { "Closing registered hook resources..." }
+        autoCloseableSet.removeIf {
+            try {
+                it.close()
+            } catch (e: Exception) {
+                log.error(e) { "An exception occurred while closing the resource. (Resource: `$it`)" }
             }
-            log.debug { "All registered hook resources have been closed." }
-        }, "Shutdown-AutoCloseable"))
+            true
+        }
+        log.debug { "All registered hook resources have been closed." }
     }
 }
 

scalabot-app/src/test/kotlin/util/UtilsKtTest.kt

@@ -1,18 +1,21 @@
 package net.lamgc.scalabot.util
 
+import io.mockk.every
+import io.mockk.justRun
+import io.mockk.mockk
+import io.mockk.verify
 import net.lamgc.scalabot.ExtensionPackageFinder
 import net.lamgc.scalabot.FinderPriority
 import net.lamgc.scalabot.FinderRules
 import net.lamgc.scalabot.FoundExtensionPackage
 import org.eclipse.aether.artifact.Artifact
 import org.eclipse.aether.artifact.DefaultArtifact
+import org.junit.jupiter.api.assertDoesNotThrow
 import org.junit.jupiter.api.assertThrows
 import java.io.File
+import java.lang.reflect.InvocationTargetException
 import java.nio.charset.StandardCharsets
-import kotlin.test.Test
-import kotlin.test.assertEquals
-import kotlin.test.assertFalse
-import kotlin.test.assertTrue
+import kotlin.test.*
 
 internal class UtilsKtTest {
 
@@ -58,4 +61,59 @@ internal class UtilsKtTest {
         }
 
     }
+
+    @Test
+    fun `AutoCloseable shutdown hook`() {
+        val utilsInternalClass = Class.forName("net.lamgc.scalabot.util.UtilsInternal")
+        val utilsInternalObject = utilsInternalClass.getDeclaredField("INSTANCE").get(null)
+            ?: fail("无法获取 UtilsInternal 对象.")
+        val doCloseResourcesMethod = utilsInternalClass.getDeclaredMethod("doCloseResources")
+            .apply {
+                isAccessible = true
+            }
+
+        // 正常的运行过程.
+        val mockResource = mockk<AutoCloseable> {
+            justRun { close() }
+        }.registerShutdownHook()
+        doCloseResourcesMethod.invoke(utilsInternalObject)
+        verify { mockResource.close() }
+
+        // 异常捕获检查.
+        val exceptionMockResource = mockk<AutoCloseable> {
+            every { close() } throws RuntimeException("Expected exception.")
+        }.registerShutdownHook()
+        assertDoesNotThrow("在关闭资源时出现未捕获异常.") {
+            doCloseResourcesMethod.invoke(utilsInternalObject)
+        }
+        verify { exceptionMockResource.close() }
+
+        // 错误抛出检查.
+        val errorMockResource = mockk<AutoCloseable> {
+            every { close() } throws Error("Expected error.")
+        }.registerShutdownHook()
+        assertThrows<Error>("关闭资源时捕获了不该捕获的 Error.") {
+            try {
+                doCloseResourcesMethod.invoke(utilsInternalObject)
+            } catch (e: InvocationTargetException) {
+                throw e.targetException
+            }
+        }
+        verify { errorMockResource.close() }
+
+        @Suppress("UNCHECKED_CAST")
+        val resourceSet = utilsInternalClass.getDeclaredMethod("getAutoCloseableSet").invoke(utilsInternalObject)
+                as MutableSet<AutoCloseable>
+        resourceSet.clear()
+
+        val closeRef = mockk<AutoCloseable> {
+            justRun { close() }
+        }
+        resourceSet.add(closeRef)
+        assertTrue(resourceSet.contains(closeRef), "测试用资源虚引用添加失败.")
+        doCloseResourcesMethod.invoke(utilsInternalObject)
+        assertFalse(resourceSet.contains(closeRef), "资源虚引用未从列表中删除.")
+
+        resourceSet.clear()
+    }
 }