Fixes #1614: Add API to clean up mocks.

Due to the introduction of map from weak reference from mock instance to
its invocation handler, Mockito became vunerable to memory leaks as
there are multiple situations where Mockito could unintentionally hold
strong references to mock instances in the map record. The strong
references could be through spiedInstance for spies, and arguments used
to faciliate method stubbing.

Mockito could never know if the arguments passed in for method stubbing
are also strongly referenced somewhere else or not, so Mockito needs to
save a strong reference to these arguments to avoid premature GC.
Therefore to solve cyclic strong references through arguments Mockito
needs to explicitly know when mocks are out of their life, and clean
up all internal strong references associated with them.

This commit also fixes #1532 and fixes #1533.

src/main/java/org/mockito/MockitoFramework.java

@@ -92,4 +92,26 @@ public interface MockitoFramework {
      */
     @Incubating
     InvocationFactory getInvocationFactory();
+
+    /**
+     * Clears up internal state of all existing mocks. This is useful when testing with {@link org.mockito.plugins.InlineMockMaker}
+     * which may hold references to mocks and leak memory. No interaction to any mock created previously is not allowed
+     * after calling this method.
+     *
+     * @since 2.24.8
+     * @see #clearMock(Object)
+     */
+    @Incubating
+    void clearAllMocks();
+
+    /**
+     * Clears up internal state of the mock. This is useful when testing with {@link org.mockito.plugins.InlineMockMaker}
+     * which may hold references to mocks and leak memory. No interaction to this mock is allowed after calling this method.
+     *
+     * @param mock the mock to clear up
+     * @since 2.24.8
+     * @see #clearAllMocks()
+     */
+    @Incubating
+    void clearMock(Object mock);
 }

src/main/java/org/mockito/internal/creation/bytebuddy/InlineByteBuddyMockMaker.java

@@ -14,6 +14,7 @@
 import org.mockito.internal.util.concurrent.WeakConcurrentMap;
 import org.mockito.invocation.MockHandler;
 import org.mockito.mock.MockCreationSettings;
+import org.mockito.plugins.InlineMockMaker;
 
 import java.io.File;
 import java.io.FileOutputStream;
@@ -89,7 +90,7 @@
  * support this feature.
  */
 @Incubating
-public class InlineByteBuddyMockMaker implements ClassCreatingMockMaker {
+public class InlineByteBuddyMockMaker implements ClassCreatingMockMaker, InlineMockMaker {
 
     private static final Instrumentation INSTRUMENTATION;
 
@@ -271,6 +272,16 @@ public void resetMock(Object mock, MockHandler newHandler, MockCreationSettings
         }
     }
 
+    @Override
+    public void clearMock(Object mock) {
+        mocks.remove(mock);
+    }
+
+    @Override
+    public void clearAllMocks() {
+        mocks.clear();
+    }
+
     @Override
     public TypeMockability isTypeMockable(final Class<?> type) {
         return new TypeMockability() {

src/main/java/org/mockito/internal/framework/DefaultMockitoFramework.java

@@ -10,6 +10,8 @@
 import org.mockito.internal.util.Checks;
 import org.mockito.invocation.InvocationFactory;
 import org.mockito.listeners.MockitoListener;
+import org.mockito.plugins.InlineMockMaker;
+import org.mockito.plugins.MockMaker;
 import org.mockito.plugins.MockitoPlugins;
 
 import static org.mockito.internal.progress.ThreadSafeMockingProgress.mockingProgress;
@@ -37,4 +39,25 @@ public MockitoPlugins getPlugins() {
     public InvocationFactory getInvocationFactory() {
         return new DefaultInvocationFactory();
     }
+
+    private InlineMockMaker getInlineMockMaker() {
+        MockMaker mockMaker = Plugins.getMockMaker();
+        return (mockMaker instanceof InlineMockMaker) ? (InlineMockMaker) mockMaker : null;
+    }
+
+    @Override
+    public void clearAllMocks() {
+        InlineMockMaker mockMaker = getInlineMockMaker();
+        if (mockMaker != null) {
+            mockMaker.clearAllMocks();
+        }
+    }
+
+    @Override
+    public void clearMock(Object mock) {
+        InlineMockMaker mockMaker = getInlineMockMaker();
+        if (mockMaker != null) {
+            mockMaker.clearMock(mock);
+        }
+    }
 }

src/main/java/org/mockito/plugins/InlineMockMaker.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2019 Mockito contributors
+ * This program is made available under the terms of the MIT License.
+ */
+
+package org.mockito.plugins;
+
+import org.mockito.Incubating;
+
+/**
+ * Extension to {@link MockMaker} for mock makers that changes inline method implementations.
+ * @since 2.24.8
+ */
+@Incubating
+public interface InlineMockMaker extends MockMaker {
+    /**
+     * Clean up internal state for specified {@code mock}. You may assume there won't be any interaction to the specific
+     * mock after this is called.
+     *
+     * @param mock the mock instance whose internal state is to be cleaned.
+     * @since 2.24.8
+     */
+    @Incubating
+    void clearMock(Object mock);
+
+    /**
+     * Cleans up internal state for all existing mocks. You may assume there won't be any interaction to mocks created
+     * previously after this is called.
+     *
+     * @since 2.24.8
+     */
+    @Incubating
+    void clearAllMocks();
+
+}

src/test/java/org/mockito/internal/creation/bytebuddy/InlineByteBuddyMockMakerTest.java

@@ -287,6 +287,31 @@ public void test_parameters_retention() throws Exception {
                 .getOnly().getParameters().getOnly().getName()).isEqualTo("bar");
     }
 
+    @Test
+    public void test_clear_mock_clears_handler() {
+        MockCreationSettings<GenericSubClass> settings = settingsFor(GenericSubClass.class);
+        GenericSubClass proxy = mockMaker.createMock(settings, new MockHandlerImpl<GenericSubClass>(settings));
+        assertThat(mockMaker.getHandler(proxy)).isNotNull();
+        mockMaker.clearMock(proxy);
+        assertThat(mockMaker.getHandler(proxy)).isNull();
+    }
+
+    @Test
+    public void test_clear_all_mock_clears_handler() {
+        MockCreationSettings<GenericSubClass> settings = settingsFor(GenericSubClass.class);
+        GenericSubClass proxy1 = mockMaker.createMock(settings, new MockHandlerImpl<GenericSubClass>(settings));
+        assertThat(mockMaker.getHandler(proxy1)).isNotNull();
+
+        settings = settingsFor(GenericSubClass.class);
+        GenericSubClass proxy2 = mockMaker.createMock(settings, new MockHandlerImpl<GenericSubClass>(settings));
+        assertThat(mockMaker.getHandler(proxy1)).isNotNull();
+
+        mockMaker.clearAllMocks();
+
+        assertThat(mockMaker.getHandler(proxy1)).isNull();
+        assertThat(mockMaker.getHandler(proxy2)).isNull();
+    }
+
     private static <T> MockCreationSettings<T> settingsFor(Class<T> type, Class<?>... extraInterfaces) {
         MockSettingsImpl<T> mockSettings = new MockSettingsImpl<T>();
         mockSettings.setTypeToMock(type);

src/test/java/org/mockito/internal/framework/DefaultMockitoFrameworkTest.java

@@ -10,14 +10,18 @@
 import org.mockito.MockSettings;
 import org.mockito.StateMaster;
 import org.mockito.exceptions.misusing.RedundantListenerException;
+import org.mockito.internal.configuration.plugins.Plugins;
 import org.mockito.listeners.MockCreationListener;
 import org.mockito.listeners.MockitoListener;
 import org.mockito.mock.MockCreationSettings;
+import org.mockito.plugins.InlineMockMaker;
 import org.mockitoutil.TestBase;
 
 import java.util.List;
 import java.util.Set;
 
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.*;
 import static org.mockitoutil.ThrowableAssert.assertThat;
 
@@ -112,5 +116,35 @@ public void run() {
                     "For more information, see the javadoc for RedundantListenerException class.");
     }
 
+    @Test
+    public void clears_all_mocks() {
+        List list1 = mock(List.class);
+        assertTrue(mockingDetails(list1).isMock());
+        List list2 = mock(List.class);
+        assertTrue(mockingDetails(list2).isMock());
+
+        framework.clearAllMocks();
+
+        if (Plugins.getMockMaker() instanceof InlineMockMaker) {
+            assertFalse(mockingDetails(list1).isMock());
+            assertFalse(mockingDetails(list2).isMock());
+        }
+    }
+
+    @Test
+    public void clears_mock() {
+        List list1 = mock(List.class);
+        assertTrue(mockingDetails(list1).isMock());
+        List list2 = mock(List.class);
+        assertTrue(mockingDetails(list2).isMock());
+
+        framework.clearMock(list1);
+
+        if (Plugins.getMockMaker() instanceof InlineMockMaker) {
+            assertFalse(mockingDetails(list1).isMock());
+            assertTrue(mockingDetails(list2).isMock());
+        }
+    }
+
     private static class MyListener implements MockitoListener {}
 }

subprojects/inline/src/test/java/org/mockitoinline/bugs/CyclicMockMethodArgumentMemoryLeakTest.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2019 Mockito contributors
+ * This program is made available under the terms of the MIT License.
+ */
+
+package org.mockitoinline.bugs;
+
+import org.junit.Test;
+
+import static org.mockito.Mockito.framework;
+import static org.mockito.Mockito.mock;
+
+public class CyclicMockMethodArgumentMemoryLeakTest {
+    private static final int ARRAY_LENGTH = 1 << 20;  // 4 MB
+
+    @Test
+    public void no_memory_leak_when_cyclically_calling_method_with_mocks() {
+        for (int i = 0; i < 100; ++i) {
+            final A a = mock(A.class);
+            a.largeArray = new int[ARRAY_LENGTH];
+            final B b = mock(B.class);
+
+            a.accept(b);
+            b.accept(a);
+
+            framework().clearAllMocks();
+        }
+    }
+
+    private static class A {
+        private int[] largeArray;
+
+        void accept(B b) {}
+    }
+
+    private static class B {
+        void accept(A a) {}
+    }
+}

subprojects/inline/src/test/java/org/mockitoinline/bugs/SelfSpyReferenceMemoryLeakTest.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2019 Mockito contributors
+ * This program is made available under the terms of the MIT License.
+ */
+
+package org.mockitoinline.bugs;
+
+import org.junit.Test;
+
+import static org.mockito.Mockito.framework;
+import static org.mockito.Mockito.spy;
+
+public class SelfSpyReferenceMemoryLeakTest {
+    private static final int ARRAY_LENGTH = 1 << 20;  // 4 MB
+
+    @Test
+    public void no_memory_leak_when_spy_holds_reference_to_self() {
+        for (int i = 0; i < 100; ++i) {
+            final DeepRefSelfClass instance = spy(new DeepRefSelfClass());
+            instance.refInstance(instance);
+
+            framework().clearAllMocks();
+        }
+    }
+
+    private static class DeepRefSelfClass {
+        private final DeepRefSelfClass[] array = new DeepRefSelfClass[1];
+
+        private final int[] largeArray = new int[ARRAY_LENGTH];
+
+        private void refInstance(DeepRefSelfClass instance) {
+            array[0] = instance;
+        }
+    }
+}