ENH: introduce conditional annotation for schema generation

data-prepper-api/src/main/java/org/opensearch/dataprepper/model/annotations/AlsoRequires.java

@@ -0,0 +1,21 @@
+package org.opensearch.dataprepper.model.annotations;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation used in schema generation to define the names and corresponding values of other required
+ * configurations if the configuration represented by the annotated field/method is present.
+ */
+@Documented
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.FIELD, ElementType.METHOD})
+public @interface AlsoRequires {
+    /**
+     * Array of Required annotations, each representing a required property with its allowed values.
+     */
+    Required[] values();
+}

data-prepper-api/src/main/java/org/opensearch/dataprepper/model/annotations/Required.java

@@ -0,0 +1,22 @@
+package org.opensearch.dataprepper.model.annotations;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * Annotation to represent a required property and its allowed values.
+ */
+@Documented
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Required {
+    /**
+     * Name of the required property.
+     */
+    String name();
+
+    /**
+     * Allowed values for the required property. The default value of {} means any non-null value is allowed.
+     */
+    String[] allowedValues() default {};
+}

data-prepper-plugin-schema/src/main/java/org/opensearch/dataprepper/schemas/JsonSchemaConverter.java

@@ -11,10 +11,15 @@
 import com.github.victools.jsonschema.generator.SchemaGeneratorConfigBuilder;
 import com.github.victools.jsonschema.generator.SchemaGeneratorConfigPart;
 import com.github.victools.jsonschema.generator.SchemaVersion;
+import org.opensearch.dataprepper.model.annotations.AlsoRequires;
 
+import java.util.Arrays;
 import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
 
 public class JsonSchemaConverter {
+    static final String KEY_VALUE_PAIR_DELIMITER = ":";
     static final String DEPRECATED_SINCE_KEY = "deprecated";
     private final List<Module> jsonSchemaGeneratorModules;
 
@@ -31,9 +36,11 @@ public ObjectNode convertIntoJsonSchema(
         final SchemaGeneratorConfigPart<FieldScope> scopeSchemaGeneratorConfigPart = configBuilder.forFields();
         overrideInstanceAttributeWithDeprecated(scopeSchemaGeneratorConfigPart);
         resolveDefaultValueFromJsonProperty(scopeSchemaGeneratorConfigPart);
+        resolveDependentRequiresFields(scopeSchemaGeneratorConfigPart);
 
         final SchemaGeneratorConfig config = configBuilder.build();
         final SchemaGenerator generator = new SchemaGenerator(config);
+
         return generator.generateSchema(clazz);
     }
 
@@ -59,4 +66,21 @@ private void resolveDefaultValueFromJsonProperty(
             return annotation == null || annotation.defaultValue().isEmpty() ? null : annotation.defaultValue();
         });
     }
+
+    private void resolveDependentRequiresFields(
+            final SchemaGeneratorConfigPart<FieldScope> scopeSchemaGeneratorConfigPart) {
+        scopeSchemaGeneratorConfigPart.withDependentRequiresResolver(field -> Optional
+                .ofNullable(field.getAnnotationConsideringFieldAndGetter(AlsoRequires.class))
+                .map(alsoRequires -> Arrays.stream(alsoRequires.values())
+                        .map(required -> {
+                            final String property = required.name();
+                            final String[] allowedValues = required.allowedValues();
+                            if (allowedValues.length == 0) {
+                                return property;
+                            }
+                            return property + KEY_VALUE_PAIR_DELIMITER + Arrays.toString(allowedValues);
+                        })
+                        .collect(Collectors.toList()))
+                .orElse(null));
+    }
 }

data-prepper-plugin-schema/src/test/java/org/opensearch/dataprepper/schemas/JsonSchemaConverterTest.java

@@ -4,12 +4,15 @@
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ArrayNode;
 import com.fasterxml.jackson.databind.node.ObjectNode;
 import com.fasterxml.jackson.databind.node.TextNode;
 import com.github.victools.jsonschema.generator.Module;
 import com.github.victools.jsonschema.generator.OptionPreset;
 import com.github.victools.jsonschema.generator.SchemaVersion;
 import org.junit.jupiter.api.Test;
+import org.opensearch.dataprepper.model.annotations.AlsoRequires;
+import org.opensearch.dataprepper.model.annotations.Required;
 import org.opensearch.dataprepper.schemas.module.CustomJacksonModule;
 
 import java.util.Collections;
@@ -53,6 +56,21 @@ void testConvertIntoJsonSchemaWithCustomJacksonModule() throws JsonProcessingExc
         assertThat(propertiesNode, instanceOf(ObjectNode.class));
         assertThat(propertiesNode.has("test_attribute_with_getter"), is(true));
         assertThat(propertiesNode.has("custom_test_attribute"), is(true));
+        final JsonNode dependentRequiredNode = jsonSchemaNode.at("/dependentRequired");
+        assertThat(dependentRequiredNode, instanceOf(ObjectNode.class));
+        assertThat(dependentRequiredNode.has("test_mutually_exclusive_attribute_a"), is(true));
+        assertThat(dependentRequiredNode.at("/test_mutually_exclusive_attribute_a"),
+                instanceOf(ArrayNode.class));
+        final ArrayNode dependentRequiredProperty1 = (ArrayNode) dependentRequiredNode.at(
+                "/test_mutually_exclusive_attribute_a");
+        assertThat(dependentRequiredProperty1.size(), equalTo(1));
+        assertThat(dependentRequiredProperty1.get(0), equalTo(
+                TextNode.valueOf("test_mutually_exclusive_attribute_b:[null, \"test_value\"]")));
+        final ArrayNode dependentRequiredProperty2 = (ArrayNode) dependentRequiredNode.at(
+                "/test_dependent_required_property_with_default_allowed_values");
+        assertThat(dependentRequiredProperty2.size(), equalTo(1));
+        assertThat(dependentRequiredProperty2.get(0), equalTo(
+                TextNode.valueOf("test_mutually_exclusive_attribute_a")));
     }
 
     @JsonClassDescription("test config")
@@ -65,6 +83,20 @@ static class TestConfig {
         @JsonProperty(defaultValue = "default_value")
         private String testAttributeWithDefaultValue;
 
+        @JsonProperty
+        @AlsoRequires(values = {
+                @Required(name="test_mutually_exclusive_attribute_b", allowedValues = {"null", "\"test_value\""})
+        })
+        private String testMutuallyExclusiveAttributeA;
+
+        private String testMutuallyExclusiveAttributeB;
+
+        @JsonProperty
+        @AlsoRequires(values = {
+                @Required(name="test_mutually_exclusive_attribute_a")
+        })
+        private String testDependentRequiredPropertyWithDefaultAllowedValues;
+
         public String getTestAttributeWithGetter() {
             return testAttributeWithGetter;
         }