Support generated ViewModel defaults and stored property access

fx/README.md

@@ -503,3 +503,7 @@ These are the `IllegalArgumentException` messages a document can produce. The vi
 | `No component found for type:` | the container was asked for a controller, component, or converter it did not scan |
 
 A conversion failure does not fail the load. It records a message, as [Converter](#converter) describes.
+
+Generated Java ViewModels can share the existing runtime storage and identity registry; see
+[the generated ViewModel runtime contract](docs/generated-viewmodels.md) for stored-property
+access, declarative service defaults, compatible overrides and module-path registration.

fx/docs/generated-viewmodels.md

@@ -0,0 +1,9 @@
+# Generated ViewModel runtime contract
+
+A generator may extend `ViewModel` with typed constructors and accessors. Accessors call the protected final `storedProperty(name)` method, which returns the existing Attribute property and never invokes a reflective accessor. Unknown stored Attributes fail explicitly. Property storage, write-back, lazy nested Models, collection contents and Messages remain owned by `ViewModel`.
+
+Modules contribute public `ViewModelRegistry` marker services annotated with repeatable `ViewModelRegistration` declarations. Each declaration names the configured Model, generated base and selected default class. Registries are inspected through `ServiceLoader.Provider.type()` without constructing them; their annotations are also available to non-initializing designer discovery. Classpath applications package `META-INF/services/de.neitzel.fx.view.ViewModelRegistry`; named modules declare `provides` and export/open generated ViewModel packages as appropriate.
+
+`ViewModelDefaults.select` checks duplicate/conflicting defaults, finds the most-specific applicable Model declaration, and requires an explicit override to extend the corresponding generated base. No declaration preserves generic/default replacement behavior. A compatible explicit request takes precedence before creation. Existing instances are reused for a requested superclass/interface that they satisfy; incompatible requests fail. Nested lazy loading uses the same registry and identity table as direct loading. Failed subclass construction removes its partially registered instance.
+
+Generated Java source and compiler integration live in NeitzelFXDesigner. This library API is a development snapshot, not a published release. Runtime regressions cover stored identity/write-back, cycles, null children, Messages, compatible/incompatible requests, most-specific defaults, provider non-execution, conflicting contributions and constructor failure cleanup. Existing ungenerated Model and Component tests remain required.

fx/src/main/java/de/neitzel/fx/view/ViewModel.java

@@ -169,6 +169,13 @@ public class ViewModel {
         }
     }
 
+    /** Returns a stored Attribute only, without invoking a generated or custom accessor. */
+    protected final Property<?> storedProperty(String name) {
+        Property<?> property = properties.get(name);
+        if (property == null) throw new IllegalArgumentException("No stored Attribute: " + name);
+        return property;
+    }
+
     /**
      * Returns the JavaFX property for an Attribute name.
      * <p>

fx/src/main/java/de/neitzel/fx/view/ViewModelDefaults.java

@@ -0,0 +1,65 @@
+package de.neitzel.fx.view;
+
+import java.util.*;
+
+/** Resolves declarative services without constructing providers or Models. */
+public final class ViewModelDefaults {
+    private ViewModelDefaults() {}
+
+    public static Class<?> select(Class<?> model, Class<?> explicit, ClassLoader loader) {
+        var entries = new HashMap<Class<?>, ViewModelRegistration>();
+        var origins = new HashMap<Class<?>, String>();
+        for (var provider : ServiceLoader.load(ViewModelRegistry.class, loader).stream().toList()) {
+            Class<?> type = provider.type();
+            for (var entry : type.getAnnotationsByType(ViewModelRegistration.class)) {
+                if (!entry.generated().isAssignableFrom(entry.defaultType())) {
+                    throw new IllegalArgumentException(
+                            "Default must extend generated ViewModel: " + type.getName());
+                }
+                var old = entries.putIfAbsent(entry.model(), entry);
+                if (old != null
+                        && (old.generated() != entry.generated()
+                                || old.defaultType() != entry.defaultType())) {
+                    throw new IllegalArgumentException(
+                            "Conflicting ViewModel defaults for "
+                                    + entry.model().getName()
+                                    + " in "
+                                    + origins.get(entry.model())
+                                    + " and "
+                                    + type.getName());
+                }
+                origins.putIfAbsent(entry.model(), type.getName());
+            }
+        }
+        var candidates =
+                entries.values().stream().filter(e -> e.model().isAssignableFrom(model)).toList();
+        var best =
+                candidates.stream()
+                        .filter(
+                                e ->
+                                        candidates.stream()
+                                                .noneMatch(
+                                                        other ->
+                                                                other != e
+                                                                        && e.model()
+                                                                                .isAssignableFrom(
+                                                                                        other
+                                                                                                .model())))
+                        .toList();
+        if (best.size() > 1)
+            throw new IllegalArgumentException(
+                    "Ambiguous ViewModel defaults for " + model.getName());
+        var chosen = best.isEmpty() ? null : best.getFirst();
+        if (explicit != null && explicit != ViewModel.class) {
+            if (chosen != null && !chosen.generated().isAssignableFrom(explicit)) {
+                throw new IllegalArgumentException(
+                        "Explicit ViewModel "
+                                + explicit.getName()
+                                + " must extend "
+                                + chosen.generated().getName());
+            }
+            return explicit;
+        }
+        return chosen == null ? ViewModel.class : chosen.defaultType();
+    }
+}

fx/src/main/java/de/neitzel/fx/view/ViewModelRegistration.java

@@ -0,0 +1,15 @@
+package de.neitzel.fx.view;
+
+import java.lang.annotation.*;
+
+/** A compiled, non-executing default declaration contributed by a registry service. */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE)
+@Repeatable(ViewModelRegistrations.class)
+public @interface ViewModelRegistration {
+    Class<?> model();
+
+    Class<? extends ViewModel> generated();
+
+    Class<? extends ViewModel> defaultType();
+}

fx/src/main/java/de/neitzel/fx/view/ViewModelRegistrations.java

@@ -0,0 +1,10 @@
+package de.neitzel.fx.view;
+
+import java.lang.annotation.*;
+
+/** Container for generated registry declarations. */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE)
+public @interface ViewModelRegistrations {
+    ViewModelRegistration[] value();
+}

fx/src/main/java/de/neitzel/fx/view/ViewModelRegistry.java

@@ -0,0 +1,7 @@
+package de.neitzel.fx.view;
+
+/**
+ * Marker service for declarative generated ViewModel registrations. Providers are never
+ * instantiated.
+ */
+public interface ViewModelRegistry {}

fx/src/main/java/de/neitzel/fx/view/ViewModels.java

@@ -47,20 +47,19 @@ final class ViewModels {
      * @return the ViewModel for that instance, or the replacement
      */
     static Object of(Object model, Class<?> viewModelClass) {
+        Class<?> selected = ViewModelDefaults.select(model.getClass(), viewModelClass, model.getClass().getClassLoader());
         Object existing = BY_INSTANCE.get(model);
         if (existing != null) {
             if (viewModelClass != null && viewModelClass != ViewModel.class
-                    && existing.getClass() != viewModelClass) {
+                    && !selected.isInstance(existing)) {
                 throw new IllegalArgumentException(
                         "ViewModel is " + existing.getClass().getName()
                                 + " but the View names " + viewModelClass.getName());
             }
             return existing;
         }
-        if (viewModelClass == null || viewModelClass == ViewModel.class) {
-            return new ViewModel(model);
-        }
-        return construct(model, viewModelClass);
+        if (selected == ViewModel.class) return new ViewModel(model);
+        return construct(model, selected);
     }
 
     /**
@@ -101,6 +100,7 @@ final class ViewModels {
             }
             return created;
         } catch (InvocationTargetException failure) {
+            BY_INSTANCE.remove(model);
             if (failure.getCause() instanceof RuntimeException runtime) {
                 throw runtime;
             }

fx/src/test/java/de/neitzel/fx/view/GeneratedViewModelTest.java

@@ -0,0 +1,152 @@
+package de.neitzel.fx.view;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import javafx.beans.property.*;
+
+import org.junit.jupiter.api.Test;
+
+public class GeneratedViewModelTest {
+    public static class Node {
+        private String name = "sample";
+        private Node child;
+
+        public String getName() {
+            return name;
+        }
+
+        public void setName(String n) {
+            name = n;
+        }
+
+        public Node getChild() {
+            return child;
+        }
+
+        public void setChild(Node n) {
+            child = n;
+        }
+    }
+
+    public static class Special extends Node {}
+
+    public static class Generated extends ViewModel {
+        public Generated(Node n) {
+            super(n);
+        }
+
+        public StringProperty nameProperty() {
+            return (StringProperty) storedProperty("name");
+        }
+
+        @SuppressWarnings("unchecked")
+        public Property<Generated> childProperty() {
+            return (Property<Generated>) (Property<?>) storedProperty("child");
+        }
+
+        public Property<?> missingProperty() {
+            return storedProperty("missing");
+        }
+    }
+
+    public static class Custom extends Generated {
+        public Custom(Node n) {
+            super(n);
+        }
+    }
+
+    public static class Other extends Generated {
+        public Other(Node n) {
+            super(n);
+        }
+    }
+
+    public static class Specific extends Generated {
+        public Specific(Special n) {
+            super(n);
+        }
+    }
+
+    @ViewModelRegistration(
+            model = Node.class,
+            generated = Generated.class,
+            defaultType = Custom.class)
+    @ViewModelRegistration(
+            model = Special.class,
+            generated = Specific.class,
+            defaultType = Specific.class)
+    public static class Registry implements ViewModelRegistry {
+        public Registry() {
+            throw new AssertionError("Provider executed");
+        }
+    }
+
+    @Test
+    void storedPropertiesWriteBackAndShareCyclesAndMessages() {
+        Node n = new Node();
+        n.setChild(n);
+        var vm = (Custom) ViewModels.of(n);
+        assertSame(vm.nameProperty(), vm.property("name"));
+        vm.nameProperty().set("changed");
+        assertEquals("changed", n.getName());
+        assertSame(vm, vm.childProperty().getValue());
+        assertSame(vm, ViewModels.of(n, Generated.class));
+        vm.addMessage(new Message(Message.Severity.INFO, "notice", "name"));
+        assertEquals("notice", vm.property("latestMessage").getValue());
+        assertThrows(IllegalArgumentException.class, vm::missingProperty);
+        assertThrows(IllegalArgumentException.class, () -> ViewModels.of(n, Other.class));
+    }
+
+    @Test
+    void explicitAndMostSpecificDefaultsAndNullChildren() {
+        Node n = new Node();
+        var custom = (Other) ViewModels.of(n, Other.class);
+        assertNull(custom.childProperty().getValue());
+        assertSame(custom, ViewModels.of(n));
+        assertInstanceOf(Specific.class, ViewModels.of(new Special()));
+        assertThrows(IllegalArgumentException.class, () -> ViewModels.of(new Node(), String.class));
+    }
+
+    @ViewModelRegistration(
+            model = Node.class,
+            generated = Generated.class,
+            defaultType = Other.class)
+    public static class Conflict implements ViewModelRegistry {}
+
+    public static class Failing extends Generated {
+        public Failing(Node n) {
+            super(n);
+            throw new IllegalStateException("failed constructor");
+        }
+    }
+
+    @Test
+    void conflictingServicesIdentifyBothOrigins() throws Exception {
+        var folder = java.nio.file.Files.createTempDirectory("viewmodel-services-");
+        var service = folder.resolve("META-INF/services/de.neitzel.fx.view.ViewModelRegistry");
+        java.nio.file.Files.createDirectories(service.getParent());
+        java.nio.file.Files.writeString(service, Conflict.class.getName());
+        try (var loader =
+                new java.net.URLClassLoader(
+                        new java.net.URL[] {folder.toUri().toURL()}, getClass().getClassLoader())) {
+            var error =
+                    assertThrows(
+                            IllegalArgumentException.class,
+                            () -> ViewModelDefaults.select(Node.class, null, loader));
+            assertTrue(error.getMessage().contains(Registry.class.getName()));
+            assertTrue(error.getMessage().contains(Conflict.class.getName()));
+        } finally {
+            try (var paths = java.nio.file.Files.walk(folder)) {
+                for (var p : paths.sorted(java.util.Comparator.reverseOrder()).toList())
+                    java.nio.file.Files.delete(p);
+            }
+        }
+    }
+
+    @Test
+    void failedConstructionDoesNotRetainPartialInstance() {
+        Node n = new Node();
+        assertThrows(IllegalStateException.class, () -> ViewModels.of(n, Failing.class));
+        assertInstanceOf(Custom.class, ViewModels.of(n));
+    }
+}

fx/src/test/resources/META-INF/services/de.neitzel.fx.view.ViewModelRegistry

@@ -0,0 +1 @@
+de.neitzel.fx.view.GeneratedViewModelTest$Registry