Fix bug where @Singleton classes bound toSelf() caused stack overflow.

TODO.md

@@ -24,9 +24,9 @@ For example:
 - [ ] Get rid of wvc compiler dependency on di
 
 ## 0.1.3
-- [ ] refactor tools/gradle start scripts to use dist instead of custom bin script
-  - [ ] have custom bin/* scripts which point to dist(s) for convenience
-- [ ] di bug: @Singleton toSelf() causes stack overflow
+- [ ] ~~refactor tools/gradle start scripts to use dist instead of custom bin script~~
+  - [ ] ~~have custom bin/* scripts which point to dist(s) for convenience~~
+- [x] di bug: @Singleton toSelf() causes stack overflow
 - [ ] `OutletContainer` trait or interface for components which can contain an `<Outlet />` child.
 - [ ] `Context` should have methods for simply finding an ancestor of a certain type without the need for a predicate.
 

util/di/src/main/java/groowt/util/di/DefaultRegistry.java

@@ -3,31 +3,58 @@ package groowt.util.di;
 import org.jetbrains.annotations.Nullable;
 
 import java.lang.annotation.Annotation;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.List;
+import java.util.*;
 import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.function.Predicate;
 
 public class DefaultRegistry implements Registry {
 
-    protected record ClassKeyBinding<T>(Class<T> key, Binding<T> binding) {}
+    protected static class BindingContainer {
 
-    protected final Collection<ClassKeyBinding<?>> classBindings = new ArrayList<>();
+        private final Map<Class<?>, Binding<?>> bindings = new HashMap<>();
+
+        @SuppressWarnings("unchecked")
+        public <T> @Nullable Binding<T> get(Class<T> key) {
+            for (final var entry : bindings.entrySet()) {
+                if (entry.getKey().isAssignableFrom(key)) {
+                    return (Binding<T>) entry.getValue();
+                }
+            }
+            return null;
+        }
+
+        public <T> void put(Class<T> key, Binding<T> binding) {
+            this.bindings.put(key, binding);
+        }
+
+        public void remove(Class<?> key) {
+            this.bindings.remove(key);
+        }
+
+        public <T> void removeIf(Class<T> key, Predicate<? super Binding<T>> filter) {
+            if (filter.test(this.get(key))) {
+                this.bindings.remove(key);
+            }
+        }
+
+        public void clear() {
+            this.bindings.clear();
+        }
+
+    }
+
+    protected final BindingContainer bindingContainer = new BindingContainer();
     protected final Collection<RegistryExtension> extensions = new ArrayList<>();
 
     @Override
     public void removeBinding(Class<?> key) {
-        this.classBindings.removeIf(classKeyBinding -> classKeyBinding.key().equals(key));
+        this.bindingContainer.remove(key);
     }
 
-    @SuppressWarnings("unchecked")
     @Override
     public <T> void removeBindingIf(Class<T> key, Predicate<Binding<T>> filter) {
-        this.classBindings.removeIf(classKeyBinding ->
-                classKeyBinding.key().equals(key) && filter.test((Binding<T>) classKeyBinding.binding())
-        );
+        this.bindingContainer.removeIf(key, filter);
     }
 
     private <E extends RegistryExtension> List<E> getAllRegistryExtensions(Class<E> extensionType) {
@@ -117,18 +144,12 @@ public class DefaultRegistry implements Registry {
     public <T> void bind(Class<T> key, Consumer<? super BindingConfigurator<T>> configure) {
         final var configurator = new SimpleBindingConfigurator<>(key);
         configure.accept(configurator);
-        this.classBindings.add(new ClassKeyBinding<>(key, configurator.getBinding()));
+        this.bindingContainer.put(key, configurator.getBinding());
     }
 
-    @SuppressWarnings("unchecked")
     @Override
-    public @Nullable <T> Binding<T> getBinding(Class<T> key) {
-        for (final var classKeyBinding : this.classBindings) {
-            if (key.isAssignableFrom(classKeyBinding.key())) {
-                return (Binding<T>) classKeyBinding.binding();
-            }
-        }
-        return null;
+    public <T> @Nullable Binding<T> getBinding(Class<T> key) {
+        return this.bindingContainer.get(key);
     }
 
     private KeyBinder<?> findKeyBinder(Class<?> keyClass) {
@@ -189,7 +210,7 @@ public class DefaultRegistry implements Registry {
 
     @Override
     public void clearAllBindings() {
-        this.classBindings.clear();
+        this.bindingContainer.clear();
         for (final var extension : this.extensions) {
             if (extension instanceof KeyBinder<?> keyBinder) {
                 keyBinder.clearAllBindings();

util/di/src/main/java/groowt/util/di/SingletonScopeHandler.java

@@ -1,8 +1,9 @@
 package groowt.util.di;
 
+import jakarta.inject.Provider;
 import jakarta.inject.Singleton;
 
-import static groowt.util.di.BindingUtil.toSingleton;
+import static groowt.util.di.BindingUtil.toLazySingleton;
 
 public final class SingletonScopeHandler implements ScopeHandler<Singleton> {
 
@@ -19,12 +20,22 @@ public final class SingletonScopeHandler implements ScopeHandler<Singleton> {
             RegistryObjectFactory objectFactory
     ) {
         final Binding<T> potentialBinding = this.owner.getBinding(dependencyClass);
-        if (potentialBinding != null) {
-            return potentialBinding;
-        } else {
-            this.owner.bind(dependencyClass, toSingleton(objectFactory.createInstance(dependencyClass)));
-            return this.owner.getBinding(dependencyClass);
+        return switch (potentialBinding) {
+            case ClassBinding<T>(Class<T> from, Class<? extends T> to) -> {
+                this.owner.bind(from, toLazySingleton(() -> objectFactory.createInstance(to)));
+                yield this.owner.getBinding(from);
             }
+            case ProviderBinding<T>(Class<T> from, Provider<? extends T> provider) -> {
+                this.owner.bind(from, toLazySingleton(provider::get));
+                yield this.owner.getBinding(from);
+            }
+            case SingletonBinding<T> singletonBinding -> singletonBinding;
+            case LazySingletonBinding<T> lazySingletonBinding -> lazySingletonBinding;
+            case null -> {
+                this.owner.bind(dependencyClass, toLazySingleton(() -> objectFactory.createInstance(dependencyClass)));
+                yield this.owner.getBinding(dependencyClass);
+            }
+        };
     }
 
     @Override

util/di/src/test/java/groowt/util/di/DefaultRegistryObjectFactoryTests.java

@@ -2,6 +2,7 @@ package groowt.util.di;
 
 import jakarta.inject.Inject;
 import jakarta.inject.Named;
+import jakarta.inject.Singleton;
 import org.junit.jupiter.api.Test;
 
 import static groowt.util.di.BindingUtil.*;
@@ -250,4 +251,25 @@ public class DefaultRegistryObjectFactoryTests {
         assertEquals("Given Greeting", g.greet());
     }
 
+    @Singleton
+    public static final class SingletonGreeter implements Greeter {
+
+        @Override
+        public String greet() {
+            return "Hello, World!";
+        }
+
+    }
+
+    @Test
+    public void singletonDoesNotOverflow() {
+        final var b = DefaultRegistryObjectFactory.Builder.withDefaults();
+        b.configureRegistry(r -> {
+            r.bind(SingletonGreeter.class, toSelf());
+        });
+        final var f = b.build();
+        final var g = f.get(SingletonGreeter.class);
+        assertEquals("Hello, World!", g.greet());
+    }
+
 }