Add @ConfigMapping validateUnknown to enable / disable validation of unknown configurations in the mapping path

cdi/src/main/java/io/smallrye/config/inject/ConfigExtension.java

@@ -101,8 +101,7 @@ protected void processConfigProperties(
 
             // Each config class is both in SmallRyeConfig and managed by a configurator bean.
             // CDI requires more beans for injection points due to binding prefix.
-            ConfigClass properties = ConfigClass.configClass(annotatedType.getJavaClass(),
-                    annotatedType.getAnnotation(ConfigProperties.class).prefix());
+            ConfigClass properties = ConfigClass.configClass(annotatedType.getJavaClass());
             configProperties.add(properties);
             configPropertiesBeans.add(properties);
         }
@@ -132,7 +131,7 @@ protected void processConfigInjectionPoints(@Observes ProcessInjectionPoint<?, ?
 
         if (injectionPoint.getAnnotated().isAnnotationPresent(ConfigProperties.class)) {
             ConfigClass properties = ConfigClass.configClass((Class<?>) injectionPoint.getType(),
-                    injectionPoint.getAnnotated().getAnnotation(ConfigProperties.class).prefix());
+                    injectionPoint.getAnnotated().getAnnotation(ConfigProperties.class).prefix(), false);
 
             // If the prefix is empty at the injection point, fallbacks to the class prefix (already registered)
             if (!properties.getPrefix().equals(ConfigProperties.UNCONFIGURED_PREFIX)) {
@@ -145,7 +144,7 @@ protected void processConfigInjectionPoints(@Observes ProcessInjectionPoint<?, ?
         // Add to SmallRyeConfig config classes with a different prefix by injection point
         if (injectionPoint.getAnnotated().isAnnotationPresent(ConfigMapping.class)) {
             ConfigClass mapping = ConfigClass.configClass((Class<?>) injectionPoint.getType(),
-                    injectionPoint.getAnnotated().getAnnotation(ConfigMapping.class).prefix());
+                    injectionPoint.getAnnotated().getAnnotation(ConfigMapping.class).prefix(), true);
             // If the prefix is empty at the injection point, fallbacks to the class prefix (already registered)
             if (!mapping.getPrefix().isEmpty()) {
                 configMappings.add(mapping);

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

@@ -26,6 +26,9 @@
  * }
  * </pre>
  *
+ * A Config Mapping must match every configuration path available in the Config system. If a property name
+ * <code>server.name</code> exists, then it must be mapped with a method <code>String name()</code>.
+ * <p>
  * This annotation is also used in CDI aware environments to scan and register Config Mappings. Otherwise, Config
  * Mapping interfaces require registration via
  * {@link SmallRyeConfigBuilder#withMapping(java.lang.Class)}.
@@ -52,6 +55,14 @@
      */
     NamingStrategy namingStrategy() default NamingStrategy.KEBAB_CASE;
 
+    /**
+     * Enable or disable the Config Mapping requirement to match every configuration path available in the Config
+     * system. By default, the validation is <b>enabled</b>.
+     *
+     * @return a boolean <code>true</code> to enable the validation, or <code>false</code> to disable it.
+     */
+    boolean validateUnknown() default true;
+
     enum NamingStrategy {
         /**
          * The method name is used as is to map the configuration property.

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

@@ -119,10 +119,12 @@ static String prefix(final String prefix, final String path) {
     public static final class ConfigClass {
         private final Class<?> klass;
         private final String prefix;
+        private final boolean validateUnknown;
 
-        public ConfigClass(final Class<?> klass, final String prefix) {
+        public ConfigClass(final Class<?> klass, final String prefix, final boolean validateUnknown) {
             this.klass = klass;
             this.prefix = prefix;
+            this.validateUnknown = validateUnknown;
         }
 
         public Class<?> getKlass() {
@@ -133,6 +135,10 @@ public String getPrefix() {
             return prefix;
         }
 
+        public boolean isValidateUnknown() {
+            return validateUnknown;
+        }
+
         @Override
         public boolean equals(final Object o) {
             if (this == o) {
@@ -151,21 +157,26 @@ public int hashCode() {
         }
 
         public static ConfigClass configClass(final Class<?> klass, final String prefix) {
-            return new ConfigClass(klass, prefix);
+            return new ConfigClass(klass, prefix, true);
+        }
+
+        public static ConfigClass configClass(final Class<?> klass, final String prefix, final boolean validateUnknown) {
+            return new ConfigClass(klass, prefix, validateUnknown);
         }
 
         public static ConfigClass configClass(final Class<?> klass) {
             if (klass.isInterface()) {
                 ConfigMapping configMapping = klass.getAnnotation(ConfigMapping.class);
                 String prefix = configMapping != null ? configMapping.prefix() : "";
-                return configClass(klass, prefix);
+                boolean validateUnknown = configMapping == null || configMapping.validateUnknown();
+                return configClass(klass, prefix, validateUnknown);
             } else {
                 ConfigProperties configProperties = klass.getAnnotation(ConfigProperties.class);
                 String prefix = configProperties != null ? configProperties.prefix() : "";
                 if (prefix.equals(ConfigProperties.UNCONFIGURED_PREFIX)) {
                     prefix = "";
                 }
-                return configClass(klass, prefix);
+                return configClass(klass, prefix, false);
             }
         }
     }

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

@@ -776,7 +776,11 @@ public final class MappingBuilder {
         private final List<String> ignoredPaths = new ArrayList<>();
 
         public void mapping(ConfigClass configClass) {
+            Assert.checkNotNullParam("configClass", configClass);
             mapping(configClass.getKlass(), configClass.getPrefix());
+            if (!configClass.isValidateUnknown()) {
+                ignoredPath(configClass.getPrefix() + ".**");
+            }
         }
 
         public void mapping(Class<?> type, String prefix) {

implementation/src/test/java/io/smallrye/config/ConfigMappingInterfaceTest.java

@@ -2659,4 +2659,20 @@ interface Nested {
             String value();
         }
     }
+
+    @Test
+    void ignoreUnknownAnnotation() {
+        SmallRyeConfig config = new SmallRyeConfigBuilder()
+                .withSources(config("ignore.value", "value", "ignore.unknown", "unknown"))
+                .withMapping(IgnoreUnknownAnnotation.class)
+                .build();
+
+        IgnoreUnknownAnnotation mapping = config.getConfigMapping(IgnoreUnknownAnnotation.class);
+        assertEquals("value", mapping.value());
+    }
+
+    @ConfigMapping(prefix = "ignore", validateUnknown = false)
+    interface IgnoreUnknownAnnotation {
+        String value();
+    }
 }