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      1 /*
      2  * Copyright (C) 2018 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.testing;
     18 
     19 import android.util.Log;
     20 
     21 import com.android.internal.annotations.VisibleForTesting;
     22 
     23 import org.junit.rules.TestRule;
     24 import org.junit.runner.Description;
     25 import org.junit.runners.model.Statement;
     26 
     27 import java.util.ConcurrentModificationException;
     28 
     29 
     30 /**
     31  * Runs the test such that mocks created in it don't use a dedicated classloader.
     32  *
     33  * This allows mocking package-private methods.
     34  *
     35  * WARNING: This is absolutely incompatible with running tests in parallel!
     36  */
     37 public class DexmakerShareClassLoaderRule implements TestRule {
     38 
     39     private static final String TAG = "ShareClassloaderRule";
     40     @VisibleForTesting
     41     static final String DEXMAKER_SHARE_CLASSLOADER_PROPERTY = "dexmaker.share_classloader";
     42 
     43     private static Thread sOwningThread = null;
     44 
     45     @Override
     46     public Statement apply(Statement base, Description description) {
     47         return apply(base::evaluate).toStatement();
     48     }
     49 
     50     /**
     51      * Runs the runnable such that mocks created in it don't use a dedicated classloader.
     52      *
     53      * This allows mocking package-private methods.
     54      *
     55      * WARNING: This is absolutely incompatible with running tests in parallel!
     56      */
     57     public static void runWithDexmakerShareClassLoader(Runnable r) {
     58         apply(r::run).run();
     59     }
     60 
     61     /**
     62      * Returns a statement that first makes sure that only one thread at the time is modifying
     63      * the property. Then actually sets the property, and runs the statement.
     64      */
     65     private static <T extends Throwable> ThrowingRunnable<T> apply(ThrowingRunnable<T> r) {
     66         return wrapInMutex(wrapInSetAndClearProperty(r));
     67     }
     68 
     69     private static <T extends Throwable> ThrowingRunnable<T> wrapInSetAndClearProperty(
     70             ThrowingRunnable<T> r) {
     71         return () -> {
     72             final String previousValue = System.getProperty(DEXMAKER_SHARE_CLASSLOADER_PROPERTY);
     73             try {
     74                 System.setProperty(DEXMAKER_SHARE_CLASSLOADER_PROPERTY, "true");
     75                 r.run();
     76             } finally {
     77                 if (previousValue != null) {
     78                     System.setProperty(DEXMAKER_SHARE_CLASSLOADER_PROPERTY, previousValue);
     79                 } else {
     80                     System.clearProperty(DEXMAKER_SHARE_CLASSLOADER_PROPERTY);
     81                 }
     82             }
     83         };
     84     }
     85 
     86     /**
     87      * Runs the given statement, and while doing so prevents other threads from running statements.
     88      */
     89     private static <T extends Throwable> ThrowingRunnable<T> wrapInMutex(ThrowingRunnable<T> r) {
     90         return () -> {
     91             final boolean isOwner;
     92             synchronized (DexmakerShareClassLoaderRule.class) {
     93                 isOwner = (sOwningThread == null);
     94                 if (isOwner) {
     95                     sOwningThread = Thread.currentThread();
     96                 } else if (sOwningThread != Thread.currentThread()) {
     97                     final RuntimeException e = new ConcurrentModificationException(
     98                             "Tried to set dexmaker.share_classloader from " + Thread.currentThread()
     99                                     + ", but was already set from " + sOwningThread);
    100                     // Also log in case exception gets swallowed.
    101                     Log.e(TAG, e.getMessage(), e);
    102                     throw e;
    103                 }
    104             }
    105             try {
    106                 r.run();
    107             } finally {
    108                 synchronized (DexmakerShareClassLoaderRule.class) {
    109                     if (isOwner) {
    110                         sOwningThread = null;
    111                     }
    112                 }
    113             }
    114         };
    115     }
    116 
    117     private interface ThrowingRunnable<T extends Throwable> {
    118         void run() throws T;
    119 
    120         default Statement toStatement() {
    121             return new Statement() {
    122                 @Override
    123                 public void evaluate() throws Throwable {
    124                     ThrowingRunnable.this.run();
    125                 }
    126             };
    127         }
    128     }
    129 }
    130