Support custom validator annotations at the nested element method

implementation/src/main/java/io/smallrye/config/SmallRyeConfigSourceInterceptors.java

@@ -0,0 +1,79 @@
+package io.smallrye.config;
+
+import java.util.Iterator;
+import java.util.List;
+
+public class SmallRyeConfigSourceInterceptors implements ConfigSourceInterceptorContext {
+    private final List<ConfigSourceInterceptor> interceptors;
+
+    private int current = 0;
+
+    public SmallRyeConfigSourceInterceptors(final List<ConfigSourceInterceptor> interceptors) {
+        this.interceptors = interceptors;
+    }
+
+    ConfigValue getValue(final String name) {
+        ConfigValue configValue = null;
+        for (int i = 0; i < interceptors.size(); i++) {
+            ConfigSourceInterceptor interceptor = interceptors.get(i);
+            configValue = interceptor.getValue(this, name);
+        }
+        return configValue;
+    }
+
+    @Override
+    public ConfigValue proceed(final String name) {
+        ConfigSourceInterceptorContext context = new ConfigSourceInterceptorContext() {
+            int position = 0;
+
+            @Override
+            public ConfigValue proceed(final String name) {
+                return interceptors.get(position++).getValue(this, name);
+            }
+
+            @Override
+            public Iterator<String> iterateNames() {
+                return null;
+            }
+
+            @Override
+            public Iterator<ConfigValue> iterateValues() {
+                return null;
+            }
+        };
+
+        return context.proceed(name);
+    }
+
+    @Override
+    public Iterator<String> iterateNames() {
+        return null;
+    }
+
+    @Override
+    public Iterator<ConfigValue> iterateValues() {
+        return null;
+    }
+
+    public static void main(String[] args) {
+        SmallRyeConfigSourceInterceptors interceptors = new SmallRyeConfigSourceInterceptors(
+                List.of(new ConfigSourceInterceptor() {
+                    @Override
+                    public ConfigValue getValue(final ConfigSourceInterceptorContext context, final String name) {
+                        return context.proceed(name);
+                    }
+                }, new ConfigSourceInterceptor() {
+                    @Override
+                    public ConfigValue getValue(final ConfigSourceInterceptorContext context, final String name) {
+                        return context.proceed(name);
+                    }
+                }, new ConfigSourceInterceptor() {
+                    @Override
+                    public ConfigValue getValue(final ConfigSourceInterceptorContext context, final String name) {
+                        throw new RuntimeException();
+                    }
+                }));
+
+        interceptors.getValue("foo.bar");
+    }
+}

validator/src/main/java/io/smallrye/config/validator/BeanValidationConfigValidator.java

@@ -96,6 +96,7 @@ default void validateProperty(
                     group = optionalGroup.get();
                 }
 
+                validatePropertyValue(property, currentPath, namingStrategy, mappingObject, problems);
                 validateMappingInterface(property.asGroup().getGroupType(), appendPropertyName(currentPath, property),
                         namingStrategy, group, problems);
             } catch (IllegalAccessException e) {

validator/src/test/java/io/smallrye/config/validator/ValidateConfigTest.java

@@ -42,6 +42,7 @@
 import io.smallrye.config.ConfigValidationException;
 import io.smallrye.config.SmallRyeConfig;
 import io.smallrye.config.SmallRyeConfigBuilder;
+import io.smallrye.config.WithDefault;
 import io.smallrye.config.WithParentName;
 
 public class ValidateConfigTest {
@@ -384,6 +385,53 @@ public interface Child extends Parent {
 
     }
 
+    @Test
+    void nestedMethodValidation() {
+        SmallRyeConfig config = new SmallRyeConfigBuilder()
+                .withValidator(new BeanValidationConfigValidatorImpl())
+                .withMapping(MethodValidation.class)
+                .build();
+
+        ConfigValidationException validationException = assertThrows(ConfigValidationException.class,
+                () -> config.getConfigMapping(MethodValidation.class));
+        List<String> validations = new ArrayList<>();
+        for (int i = 0; i < validationException.getProblemCount(); i++) {
+            validations.add(validationException.getProblem(i).getMessage());
+        }
+
+        assertEquals(1, validationException.getProblemCount());
+        assertTrue(validations.contains("method.validation.nested validation executed"));
+    }
+
+    @ConfigMapping(prefix = "method.validation")
+    interface MethodValidation {
+        @NestedValidation
+        Nested nested();
+
+        interface Nested {
+            @WithDefault("value")
+            String value();
+        }
+    }
+
+    @Target({ METHOD, TYPE })
+    @Retention(RUNTIME)
+    @Constraint(validatedBy = { NestedValidator.class })
+    public @interface NestedValidation {
+        String message() default "validation executed";
+
+        Class<?>[] groups() default {};
+
+        Class<? extends Payload>[] payload() default {};
+    }
+
+    public static class NestedValidator implements ConstraintValidator<NestedValidation, MethodValidation.Nested> {
+        @Override
+        public boolean isValid(final MethodValidation.Nested value, final ConstraintValidatorContext context) {
+            return false;
+        }
+    }
+
     private static void assertValidationsEqual(List<String> validations, String... expectedProblemMessages) {
         List<String> remainingActual = new ArrayList<>(validations);
         List<String> remainingExpected = Stream.of(expectedProblemMessages).collect(Collectors.toList());