Expose _something_ from private modules used in tests where the test …

…is validating that the parent can't re-bind something from the private module. If nothing is exposed, the child/private injector can otherwise be immediately GC'd (which then allows the parent to have the binding). (Note that there are other ways the child/private module could be captured: such as a Provider or its Injector being captured into a longer-lived Thread... but this is the simplest way to do it). This is happening with some regularity on the Github Actions tests, making the tests a bit flaky.

PiperOrigin-RevId: 529467328

core/test/com/google/inject/PrivateModuleTest.java

@@ -646,19 +646,30 @@ private static class ManyPrivateModules extends AbstractModule {
     @Override
     protected void configure() {
       // make sure duplicate sources are collapsed
-      install(new FailingPrivateModule());
-      install(new FailingPrivateModule());
+      install(new FailingPrivateModule("a"));
+      install(new FailingPrivateModule("b"));
       // but additional sources are listed
-      install(new SecondFailingPrivateModule());
+      install(new SecondFailingPrivateModule("c"));
     }
   }
 
   private static class FailingPrivateModule extends PrivateModule {
+    private final String exposeAs;
+
+    FailingPrivateModule(String exposeAs) {
+      this.exposeAs = exposeAs;
+    }
+
     @Override
     protected void configure() {
       Key<List<String>> key = new Key<List<String>>() {};
       bind(key).toInstance(new ArrayList<String>());
 
+      // Expose _something_ so that the child/private injector doesn't immediately get GC'd.
+      Key<String> exposedKey = new Key<String>(Names.named(exposeAs)) {};
+      bind(exposedKey).toInstance("exposed");
+      expose(exposedKey);
+
       // Add the Provider<List> binding, created just-in-time,
       // to make sure our linked JIT bindings have the correct source.
       getProvider(key);
@@ -672,11 +683,22 @@ protected void configure() {
 
   /** A second class, so we can see another name in the source list. */
   private static class SecondFailingPrivateModule extends PrivateModule {
+    private final String exposeAs;
+
+    SecondFailingPrivateModule(String exposeAs) {
+      this.exposeAs = exposeAs;
+    }
+
     @Override
     protected void configure() {
       Key<List<String>> key = new Key<List<String>>() {};
       bind(key).toInstance(new ArrayList<String>());
 
+      // Expose _something_ so that the child/private injector doesn't immediately get GC'd.
+      Key<String> exposedKey = new Key<String>(Names.named(exposeAs)) {};
+      bind(exposedKey).toInstance("exposed");
+      expose(exposedKey);
+
       // Add the Provider<List> binding, created just-in-time,
       // to make sure our linked JIT bindings have the correct source.
       getProvider(key);

core/test/com/google/inject/errors/ChildBindingAlreadySetErrorTest.java

@@ -7,13 +7,15 @@
 import com.google.inject.AbstractModule;
 import com.google.inject.ConfigurationException;
 import com.google.inject.CreationException;
+import com.google.inject.Exposed;
 import com.google.inject.Guice;
 import com.google.inject.Injector;
 import com.google.inject.PrivateModule;
 import com.google.inject.Provides;
 import com.google.inject.internal.InternalFlags;
 import com.google.inject.internal.InternalFlags.IncludeStackTraceOption;
 import javax.inject.Inject;
+import javax.inject.Named;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -42,6 +44,14 @@ static class ChildModule extends PrivateModule {
     protected void configure() {
       bind(Foo.class).to(SubFoo.class);
     }
+
+    // Expose _something_ so that the child/private injector doesn't immediately get GC'd.
+    @Provides
+    @Named("ChildModule")
+    @Exposed
+    String provideExposed() {
+      return "a";
+    }
   }
 
   @Test
@@ -61,6 +71,14 @@ protected void configure() {}
     Foo provideFoo() {
       return new Foo();
     }
+
+    // Expose _something_ so that the child/private injector doesn't immediately get GC'd.
+    @Provides
+    @Named("Child2Module")
+    @Exposed
+    String provideExposed() {
+      return "a";
+    }
   }
 
   static class DependsOnFoo {
@@ -106,13 +124,29 @@ protected void configure() {
       // Trigger a JIT binding for DependsOnFoo in this PrivateModule.
       getProvider(DependsOnFoo.class);
     }
+
+    // Expose _something_ so that the child/private injector doesn't immediately get GC'd.
+    @Provides
+    @Named("Child3Module")
+    @Exposed
+    String provideExposed() {
+      return "a";
+    }
   }
 
   static class ChildModule4 extends PrivateModule {
     @Override
     protected void configure() {
       bind(DependsOnFoo.class).toInstance(new DependsOnFoo(new Foo()));
     }
+
+    // Expose _something_ so that the child/private injector doesn't immediately get GC'd.
+    @Provides
+    @Named("Child4Module")
+    @Exposed
+    String provideExposed() {
+      return "a";
+    }
   }
 
   @Test