Hilt: allow custom injection support for tests.

java/dagger/hilt/EntryPoint.java

@@ -17,6 +17,7 @@
 package dagger.hilt;
 
 import static java.lang.annotation.RetentionPolicy.CLASS;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
 
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
@@ -44,7 +45,7 @@
  *
  * @see <a href="https://dagger.dev/hilt/entry-points">Entry points</a>
  */
-@Retention(CLASS)
+@Retention(RUNTIME)
 @Target(ElementType.TYPE)
 @GeneratesRootInput
 public @interface EntryPoint {}

java/dagger/hilt/android/internal/managers/BUILD

@@ -33,6 +33,7 @@ android_library(
         "SavedStateHandleModule.java",
         "ServiceComponentManager.java",
         "ViewComponentManager.java",
+        "TestInjectInterceptor.java",
     ],
     exports = [":saved_state_handle_holder"],
     deps = [

java/dagger/hilt/android/internal/managers/TestInjectInterceptor.java

@@ -0,0 +1,23 @@
+package dagger.hilt.android.internal.managers;
+
+/**
+ * This class does nothing in production or in tests when running under Hilt testing framework. However, the calls
+ * to TestInjectInterceptor.injectForTesting() are done in a few strategic places just before Hilt does the injection
+ * into Android Components.
+ *
+ * As a result this class enables non-Hilt based frameworks to take over the injection process.
+ */
+public class TestInjectInterceptor {
+    /**
+     * This method always returns false by default. However, if this method is intercepted during testing
+     * by frameworks like Robolectric, the intercepting code can take over the injection process and
+     * instruct Hilt to skip doing anything extra for this instance.
+     *
+     * Return false if no custom injection was done and Hilt should continue as normal. Return true
+     * if the testing framework has takes over the injection process and Hilt should skip any extra
+     * work.
+     */
+    public static boolean injectForTesting(Object injectTo) {
+        return false;
+    }
+}

java/dagger/hilt/android/processor/internal/androidentrypoint/Generators.java

@@ -379,6 +379,9 @@ && ancestorExtendsGeneratedHiltClass(metadata)) {
         methodSpecBuilder
             .beginControlFlow("if (!injected)")
             .addStatement("injected = true")
+                .beginControlFlow("if ($T.injectForTesting(this))", ClassNames.TEST_INJECT_INTERCEPTOR)
+                .addStatement("return")
+                .endControlFlow()
             .addStatement(
                 "(($T) $L).$L($L)",
                 metadata.injectorClassName(),
@@ -395,6 +398,10 @@ && ancestorExtendsGeneratedHiltClass(metadata)) {
             .beginControlFlow("if (!injected)")
             .beginControlFlow("synchronized (injectedLock)")
             .beginControlFlow("if (!injected)")
+                .beginControlFlow("if ($T.injectForTesting(this))", ClassNames.TEST_INJECT_INTERCEPTOR)
+                .addStatement("injected = true")
+                .addStatement("return")
+                .endControlFlow()
             .addStatement(
                 "(($T) $T.generatedComponent(context)).$L($L)",
                 metadata.injectorClassName(),

java/dagger/hilt/android/proguard-rules.pro

@@ -1,3 +1,4 @@
 # Keep for the reflective cast done in EntryPoints.
 # See b/183070411#comment4 for more info.
--keep,allowobfuscation,allowshrinking @dagger.hilt.android.EarlyEntryPoint class *
+-keep,allowobfuscation,allowshrinking @dagger.hilt.android.EarlyEntryPoint class *
+-assumenosideeffects class dagger.hilt.android.internal.managers.TestInjectInterceptor { *; }

java/dagger/hilt/android/qualifiers/ActivityContext.java

@@ -24,6 +24,6 @@
 
 /** Annotation for a {@code Context} that corresponds to the activity. */
 @Qualifier
-@Retention(RetentionPolicy.CLASS)
+@Retention(RetentionPolicy.RUNTIME)
 @Target({ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD})
 public @interface ActivityContext {}

java/dagger/hilt/android/qualifiers/ApplicationContext.java

@@ -17,10 +17,13 @@
 package dagger.hilt.android.qualifiers;
 
 import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 import javax.inject.Qualifier;
 
 /** Annotation for an Application Context dependency. */
 @Qualifier
+@Retention(RetentionPolicy.RUNTIME)
 @Target({ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD})
 public @interface ApplicationContext {}

java/dagger/hilt/processor/internal/ClassNames.java

@@ -162,6 +162,8 @@ public final class ClassNames {
       get("dagger.hilt.android.internal.testing", "InternalTestRoot");
   public static final ClassName TEST_INJECTOR =
       get("dagger.hilt.android.internal.testing", "TestInjector");
+
+  public static final ClassName TEST_INJECT_INTERCEPTOR = get("dagger.hilt.android.internal.managers", "TestInjectInterceptor");
   public static final ClassName TEST_APPLICATION_COMPONENT_MANAGER =
       get("dagger.hilt.android.internal.testing", "TestApplicationComponentManager");
   public static final ClassName TEST_APPLICATION_COMPONENT_MANAGER_HOLDER =