Make @Lazy work on a package/module level

blackbox-test-inject/src/main/java/org/example/myapp/lazy2/LazyOneA.java

@@ -0,0 +1,26 @@
+package org.example.myapp.lazy2;
+
+import io.avaje.inject.PostConstruct;
+import jakarta.inject.Singleton;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+@Singleton
+public class LazyOneA {
+
+  public static final AtomicBoolean AINIT = new AtomicBoolean();
+  public static final AtomicBoolean A_POST_CONSTRUCT = new AtomicBoolean();
+
+  LazyOneA() {
+    AINIT.set(true);
+  }
+
+  @PostConstruct
+  void postConstruct() {
+    A_POST_CONSTRUCT.set(true);
+  }
+
+  public String oneA() {
+    return "oneA";
+  }
+}

blackbox-test-inject/src/main/java/org/example/myapp/lazy2/LazyOneB.java

@@ -0,0 +1,34 @@
+package org.example.myapp.lazy2;
+
+import jakarta.inject.Inject;
+import jakarta.inject.Singleton;
+import org.example.myapp.HelloService;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+@Singleton
+public class LazyOneB {
+
+  public static final AtomicBoolean BINIT = new AtomicBoolean();
+
+  final HelloService helloService;
+
+  @Inject
+  LazyOneB(HelloService helloService) {
+    this.helloService = helloService; // non-lazy dependency
+    BINIT.set(true);
+  }
+
+  /** Required by Lazy proxy */
+  LazyOneB() {
+    this.helloService = null;
+  }
+
+  public String oneB() {
+    return "oneB";
+  }
+
+  public HelloService helloService() {
+    return helloService;
+  }
+}

blackbox-test-inject/src/main/java/org/example/myapp/lazy2/LazyTwo.java

@@ -0,0 +1,44 @@
+package org.example.myapp.lazy2;
+
+import jakarta.inject.Inject;
+import jakarta.inject.Singleton;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+@Singleton
+public class LazyTwo {
+
+  public static final AtomicBoolean INIT = new AtomicBoolean();
+
+  private final LazyOneB oneB;
+  final LazyOneA oneA;
+
+  @Inject
+  LazyTwo(LazyOneA oneA, LazyOneB oneB) {
+    this.oneA = oneA;
+    this.oneB = oneB;
+    INIT.set(true);
+  }
+
+  /** Required by Lazy proxy */
+  LazyTwo() {
+    this.oneA = null;
+    this.oneB = null;
+  }
+
+  String something() {
+    return "two-" + oneA.oneA() + "-" + oneB.oneB();
+  }
+
+  String description() {
+    return this.getClass() + "|" + oneA.getClass() + "|" + oneB.getClass();
+  }
+
+  public LazyOneA oneA() {
+    return oneA;
+  }
+
+  public LazyOneB oneB() {
+    return oneB;
+  }
+}

blackbox-test-inject/src/main/java/org/example/myapp/lazy2/package-info.java

@@ -0,0 +1,9 @@
+/**
+ * Use Lazy for all the beans in this package.
+ * <p>
+ * Use {@code enforceProxy = true} to fail compilation if there is no default constructor/lazy not supported.
+ */
+@Lazy(enforceProxy = true)
+package org.example.myapp.lazy2;
+
+import io.avaje.inject.Lazy;

blackbox-test-inject/src/test/java/org/example/myapp/lazy2/LazyTwoTest.java

@@ -0,0 +1,50 @@
+package org.example.myapp.lazy2;
+
+import io.avaje.inject.BeanScope;
+import org.example.myapp.HelloService;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class LazyTwoTest {
+
+  @Test
+  void test() {
+    try (var scope = BeanScope.builder().build()) {
+      assertThat(LazyTwo.INIT).isFalse();
+      assertThat(LazyOneA.AINIT).describedAs("Only 1 constructor, so <init> called by LazyOneA$$Lazy()").isTrue();
+      assertThat(LazyOneA.A_POST_CONSTRUCT).isFalse();
+      assertThat(LazyOneB.BINIT).isFalse();
+
+      var lazyOneA = scope.get(LazyOneA.class);
+      assertThat(LazyOneA.A_POST_CONSTRUCT).describedAs("Only got the proxy").isFalse();
+
+      var lazy = scope.get(LazyTwo.class);
+      assertThat(lazy.getClass().toString()).describedAs("got the proxy").contains("LazyTwo$Lazy");
+      assertThat(LazyTwo.INIT).isFalse();
+      assertThat(LazyOneB.BINIT).isFalse();
+      assertThat(LazyOneA.A_POST_CONSTRUCT).describedAs("Only got the proxy").isFalse();
+
+      assertThat(lazy.oneA()).describedAs("same proxy instance").isSameAs(lazyOneA);
+
+      // invocation will initialize the lazy beans
+      String value = lazy.something();
+      assertThat(value).isEqualTo("two-oneA-oneB");
+      assertThat(LazyTwo.INIT).isTrue();
+      assertThat(LazyOneA.A_POST_CONSTRUCT).isTrue();
+      assertThat(LazyOneB.BINIT).isTrue();
+
+      // the graph is of Lazy beans
+      String description = lazy.description();
+      assertThat(description).describedAs("this is the underlying real instance").doesNotContain("LazyTwo$Lazy");
+      assertThat(description).contains("LazyOneA$Lazy");
+      assertThat(description).contains("LazyOneB$Lazy");
+
+      assertThat(scope.get(LazyTwo.class)).isSameAs(lazy);
+
+      HelloService nonLazyDependency = lazy.oneB().helloService();
+      HelloService helloService = scope.get(HelloService.class);
+      assertThat(nonLazyDependency).isSameAs(helloService);
+    }
+  }
+}

inject-generator/src/main/java/io/avaje/inject/generator/BeanReader.java

@@ -85,10 +85,10 @@ final class BeanReader {
         factory);
 
     typeReader.process();
-    this.lazy =
-      !FactoryPrism.isPresent(actualType)
-        && (LazyPrism.isPresent(actualType)
-        || importedComponent && ProcessingContext.isImportedLazy(actualType));
+    var lazyPrism = Util.isLazy(actualType);
+    this.lazy = !FactoryPrism.isPresent(actualType)
+      && (lazyPrism != null
+      || importedComponent && ProcessingContext.isImportedLazy(actualType));
 
     this.requestParams = new BeanRequestParams(type);
     this.name = typeReader.name();
@@ -105,6 +105,14 @@ final class BeanReader {
     this.delayed = shouldDelay();
     this.lazyProxyType = !lazy || delayed ? null : Util.lazyProxy(actualType);
     this.proxyLazy = lazy && lazyProxyType != null;
+    if (lazy && !proxyLazy) {
+      if (lazyPrism != null && lazyPrism.enforceProxy()) {
+        logError(beanType, "Lazy beans must have an additional no-arg constructor");
+      } else {
+        logWarn(beanType, "Lazy beans should have an additional no-arg constructor");
+      }
+    }
+
     conditions.readAll(actualType);
   }
 
@@ -197,8 +205,6 @@ BeanReader read() {
     conditions.addImports(importTypes);
     if (proxyLazy) {
       SimpleBeanLazyWriter.write(APContext.elements().getPackageOf(beanType), lazyProxyType);
-    } else if (lazy) {
-      logWarn(beanType, "Lazy beans should have a no-arg constructor");
     }
     return this;
   }

inject-generator/src/main/java/io/avaje/inject/generator/MethodReader.java

@@ -1,5 +1,6 @@
 package io.avaje.inject.generator;
 
+import static io.avaje.inject.generator.APContext.logError;
 import static io.avaje.inject.generator.APContext.logWarn;
 import static io.avaje.inject.generator.Constants.CONDITIONAL_DEPENDENCY;
 import static io.avaje.inject.generator.ProcessingContext.asElement;
@@ -71,10 +72,18 @@ final class MethodReader {
       primary = PrimaryPrism.isPresent(element);
       secondary = SecondaryPrism.isPresent(element);
       priority = Util.priority(element);
-      lazy = LazyPrism.isPresent(element) || LazyPrism.isPresent(element.getEnclosingElement());
+      var lazyPrism = Util.isLazy(element);
+      lazy = lazyPrism != null;
       conditions.readAll(element);
       this.lazyProxyType = lazy ? Util.lazyProxy(element) : null;
       this.proxyLazy = lazy && lazyProxyType != null;
+      if (lazy && !proxyLazy) {
+        if (lazyPrism.enforceProxy()) {
+          logError(element, "Lazy return type must be abstract or have a no-arg constructor");
+        } else {
+          logWarn(element, "Lazy return type should be abstract or have a no-arg constructor");
+        }
+      }
     } else {
       prototype = false;
       primary = false;
@@ -181,8 +190,6 @@ MethodReader read() {
     observeParameter = params.stream().filter(MethodParam::observeEvent).findFirst().orElse(null);
     if (proxyLazy) {
       SimpleBeanLazyWriter.write(APContext.elements().getPackageOf(element), lazyProxyType);
-    } else if (lazy) {
-      logWarn(element, "Lazy return types should be abstract or have a no-arg constructor");
     }
     return this;
   }

inject-generator/src/main/java/io/avaje/inject/generator/Util.java

@@ -442,4 +442,11 @@ static Integer priority(Element element) {
   private static boolean isPriorityAnnotation(AnnotationMirror mirror) {
     return mirror.getAnnotationType().asElement().getSimpleName().toString().contains("Priority");
   }
+
+  static LazyPrism isLazy(Element element) {
+    if (element == null) {
+      return null;
+    }
+    return LazyPrism.getOptionalOn(element).orElseGet(() -> isLazy(element.getEnclosingElement()));
+  }
 }

inject/src/main/java/io/avaje/inject/Lazy.java

@@ -15,5 +15,12 @@
  * constructor, a generated proxy bean will be wired for ultimate laziness.
  */
 @Retention(RetentionPolicy.SOURCE)
-@Target({ElementType.METHOD, ElementType.TYPE})
-public @interface Lazy {}
+@Target({ElementType.METHOD, ElementType.TYPE, ElementType.PACKAGE, ElementType.MODULE})
+public @interface Lazy {
+
+  /**
+   * Ensures that a compile-time proxy is generated, will fail compilation if missing conditions for
+   * generation
+   */
+  boolean enforceProxy() default false;
+}