feat(databind): add parser validation for required fields and collection types

PRDs/20251224-codegen-quality/implementation-plan.md

@@ -249,16 +249,16 @@ This PR creates the databind bootstrap infrastructure and regenerates the databi
 
 ---
 
-## PR 4: Parser Required Field Validation
+## PR 4: Parser Required Field Validation ✅
 
 | Attribute | Value |
 |-----------|-------|
-| **Files Changed** | ~10 |
+| **Files Changed** | ~25 |
 | **Risk Level** | Medium |
 | **Dependencies** | PR 1 |
 | **Target Branch** | develop |
-| **Status** | Pending |
-| **Pull Request** | |
+| **Status** | Completed |
+| **Pull Request** | [#593](https://github.com/metaschema-framework/metaschema-java/pull/593) |
 
 This PR adds validation during parsing to emit meaningful errors when required fields are missing, and includes type compatibility validation for collection class overrides.
 
@@ -294,15 +294,18 @@ Currently, when a required field/flag is missing from input data, the generated
 
 ### Acceptance Criteria
 
-- [ ] Parser validates required fields are present during deserialization
-- [ ] Missing required field produces clear error with field name and location
-- [ ] Collection class override validates type compatibility (List/Map)
-- [ ] Validation is efficient (no per-field overhead)
-- [ ] Unit tests for required field validation
-- [ ] Unit tests for collection class type validation
-- [ ] `mvn checkstyle:check` passes
-- [ ] All tests pass: `mvn test`
-- [ ] Build succeeds: `mvn clean install -PCI -Prelease`
+- [x] Parser validates required fields are present during deserialization
+- [x] Missing required field produces clear error with field name and location
+- [x] Collection class override validates type compatibility (Collection/Map)
+- [x] Validation is efficient (no per-field overhead)
+- [x] Choice group support - only error if ALL options in choice are missing
+- [x] Unit tests for required field validation
+- [x] Unit tests for collection class type validation
+- [x] Required field validation enabled by default
+- [x] CLI validators disable required field validation (schema handles it)
+- [x] `mvn checkstyle:check` passes
+- [x] All tests pass: `mvn test`
+- [x] Build succeeds: `mvn clean install -PCI -Prelease`
 
 ---
 
@@ -313,7 +316,7 @@ Currently, when a required field/flag is missing from input data, the generated
 | 1 | Code generator improvements + metaschema-testing regeneration | 20 | Low | None | ✅ Completed ([#577](https://github.com/metaschema-framework/metaschema-java/pull/577)) |
 | 2 | Collection class override support | ~15 | Low | PR 1 | ✅ Completed ([#584](https://github.com/metaschema-framework/metaschema-java/pull/584)) |
 | 3 | Databind bootstrap setup + regeneration | ~55 | Medium | PR 1, PR 2 | ✅ Completed (combined with PR 2) |
-| 4 | Parser required field validation | ~10 | Medium | PR 1 | Pending |
+| 4 | Parser required field validation | ~25 | Medium | PR 1 | ✅ Completed ([#593](https://github.com/metaschema-framework/metaschema-java/pull/593)) |
 
 **Total Estimated PRs**: 4 (3 actual - PR 2 and PR 3 combined)
 **Total Estimated Files**: ~100

databind/src/main/java/gov/nist/secauto/metaschema/databind/IBindingContext.java

@@ -447,6 +447,8 @@ default IConstraintValidator newValidator(
       @Nullable IConfiguration<ValidationFeature<?>> config) {
     IBoundLoader loader = newBoundLoader();
     loader.disableFeature(DeserializationFeature.DESERIALIZE_VALIDATE_CONSTRAINTS);
+    // Disable required field validation since schema validation handles this
+    loader.disableFeature(DeserializationFeature.DESERIALIZE_VALIDATE_REQUIRED_FIELDS);
 
     DynamicContext context = new DynamicContext();
     context.setDocumentLoader(loader);
@@ -570,6 +572,8 @@ default IValidationResult validateWithConstraints(
       throws IOException, ConstraintValidationException {
     IBoundLoader loader = newBoundLoader();
     loader.disableFeature(DeserializationFeature.DESERIALIZE_VALIDATE_CONSTRAINTS);
+    // Disable required field validation since schema validation handles this
+    loader.disableFeature(DeserializationFeature.DESERIALIZE_VALIDATE_REQUIRED_FIELDS);
     IDocumentNodeItem nodeItem = loader.loadAsNodeItem(target);
 
     return validate(nodeItem, loader, config);

databind/src/main/java/gov/nist/secauto/metaschema/databind/codegen/config/DefaultBindingConfiguration.java

@@ -15,6 +15,7 @@
 import gov.nist.secauto.metaschema.databind.IBindingContext;
 import gov.nist.secauto.metaschema.databind.codegen.ClassUtils;
 import gov.nist.secauto.metaschema.databind.config.binding.MetaschemaBindings;
+import gov.nist.secauto.metaschema.databind.io.BindingException;
 import gov.nist.secauto.metaschema.databind.io.Format;
 import gov.nist.secauto.metaschema.databind.io.IDeserializer;
 
@@ -25,6 +26,7 @@
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.nio.file.Path;
+import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -295,8 +297,10 @@ public MetaschemaBindingConfiguration addMetaschemaBindingConfiguration(
    *          the configuration resource
    * @throws IOException
    *           if an error occurred while reading the {@code file}
+   * @throws BindingException
+   *           if an error occurred while processing the binding configuration
    */
-  public void load(Path file) throws IOException {
+  public void load(Path file) throws IOException, BindingException {
     URL resource = file.toAbsolutePath().normalize().toUri().toURL();
     load(resource);
   }
@@ -308,8 +312,10 @@ public void load(Path file) throws IOException {
    *          the configuration resource
    * @throws IOException
    *           if an error occurred while reading the {@code file}
+   * @throws BindingException
+   *           if an error occurred while processing the binding configuration
    */
-  public void load(File file) throws IOException {
+  public void load(File file) throws IOException, BindingException {
     load(file.toPath());
   }
 
@@ -320,8 +326,10 @@ public void load(File file) throws IOException {
    *          the configuration resource
    * @throws IOException
    *           if an error occurred while reading the {@code resource}
+   * @throws BindingException
+   *           if an error occurred while processing the binding configuration
    */
-  public void load(URL resource) throws IOException {
+  public void load(URL resource) throws IOException, BindingException {
     IBindingContext context = IBindingContext.newInstance();
     IDeserializer<MetaschemaBindings> deserializer = context.newDeserializer(Format.XML, MetaschemaBindings.class);
 
@@ -364,7 +372,7 @@ private void processModelBindingConfig(MetaschemaBindings.ModelBinding model) {
   }
 
   private void processMetaschemaBindingConfig(URL configResource, MetaschemaBindings.MetaschemaBinding metaschema)
-      throws MalformedURLException, URISyntaxException {
+      throws MalformedURLException, URISyntaxException, BindingException {
     String href = metaschema.getHref().toString();
     URL moduleUrl = new URL(configResource, href);
     String moduleUri = ObjectUtils.notNull(moduleUrl.toURI().normalize().toString());
@@ -441,14 +449,16 @@ private void processMetaschemaBindingConfig(URL configResource, MetaschemaBindin
    *          function to extract the Java config from a binding
    * @param collectionClassAccessor
    *          function to extract the collection class name from a Java config
+   * @throws BindingException
+   *           if the collection class is invalid or cannot be found
    */
   private static <P, J> void processPropertyBindings(
       @NonNull MetaschemaBindingConfiguration metaschemaConfig,
       @NonNull String definitionName,
       @Nullable List<P> propertyBindings,
       @NonNull Function<P, String> nameAccessor,
       @NonNull Function<P, J> javaAccessor,
-      @NonNull Function<J, String> collectionClassAccessor) {
+      @NonNull Function<J, String> collectionClassAccessor) throws BindingException {
     if (propertyBindings == null) {
       return;
     }
@@ -466,13 +476,52 @@ private static <P, J> void processPropertyBindings(
 
       String collectionClassName = collectionClassAccessor.apply(java);
       if (collectionClassName != null) {
+        // Validate the collection class
+        validateCollectionClass(collectionClassName, definitionName, propertyName);
+
         IMutablePropertyBindingConfiguration config = new DefaultPropertyBindingConfiguration();
         config.setCollectionClassName(collectionClassName);
         metaschemaConfig.addPropertyBindingConfig(definitionName, propertyName, config);
       }
     }
   }
 
+  /**
+   * Validate that the specified collection class exists and implements a
+   * supported collection interface (Collection or Map).
+   *
+   * @param collectionClassName
+   *          the fully qualified class name to validate
+   * @param definitionName
+   *          the name of the containing definition (for error messages)
+   * @param propertyName
+   *          the name of the property (for error messages)
+   * @throws BindingException
+   *           if the class cannot be found or does not implement a supported
+   *           collection interface
+   */
+  private static void validateCollectionClass(
+      @NonNull String collectionClassName,
+      @NonNull String definitionName,
+      @NonNull String propertyName) throws BindingException {
+    Class<?> collectionClass;
+    try {
+      collectionClass = Class.forName(collectionClassName);
+    } catch (ClassNotFoundException ex) {
+      throw new BindingException(String.format(
+          "Collection class '%s' for property '%s' in definition '%s' could not be found",
+          collectionClassName, propertyName, definitionName), ex);
+    }
+
+    // Check if the class implements Collection or Map
+    if (!Collection.class.isAssignableFrom(collectionClass) && !Map.class.isAssignableFrom(collectionClass)) {
+      throw new BindingException(String.format(
+          "Collection class '%s' for property '%s' in definition '%s' must implement "
+              + "java.util.Collection or java.util.Map",
+          collectionClassName, propertyName, definitionName));
+    }
+  }
+
   /**
    * Process property bindings from a define-assembly-binding element.
    *
@@ -482,11 +531,14 @@ private static <P, J> void processPropertyBindings(
    *          the name of the containing definition
    * @param propertyBindings
    *          the list of property bindings to process
+   * @throws BindingException
+   *           if the collection class is invalid or cannot be found
    */
   private static void processAssemblyPropertyBindings(
       @NonNull MetaschemaBindingConfiguration metaschemaConfig,
       @NonNull String definitionName,
-      @Nullable List<MetaschemaBindings.MetaschemaBinding.DefineAssemblyBinding.PropertyBinding> propertyBindings) {
+      @Nullable List<MetaschemaBindings.MetaschemaBinding.DefineAssemblyBinding.PropertyBinding> propertyBindings)
+      throws BindingException {
     processPropertyBindings(
         metaschemaConfig,
         definitionName,
@@ -505,11 +557,14 @@ private static void processAssemblyPropertyBindings(
    *          the name of the containing definition
    * @param propertyBindings
    *          the list of property bindings to process
+   * @throws BindingException
+   *           if the collection class is invalid or cannot be found
    */
   private static void processFieldPropertyBindings(
       @NonNull MetaschemaBindingConfiguration metaschemaConfig,
       @NonNull String definitionName,
-      @Nullable List<MetaschemaBindings.MetaschemaBinding.DefineFieldBinding.PropertyBinding> propertyBindings) {
+      @Nullable List<MetaschemaBindings.MetaschemaBinding.DefineFieldBinding.PropertyBinding> propertyBindings)
+      throws BindingException {
     processPropertyBindings(
         metaschemaConfig,
         definitionName,