allow @Conditional on property, that asserts a sibling value

jsonschema-module-expressive-annotations/src/main/java/io/github/axonivy/json/schema/annotations/Conditional.java

@@ -0,0 +1,37 @@
+package io.github.axonivy.json.schema.annotations;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Repeatable;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Documents fields which only will be present, if a sibling has a certain value.
+ *
+ * @see "https://json-schema.org/understanding-json-schema/reference/conditionals.html"
+ * @see Condition
+ *
+ */
+@Repeatable(Conditional.List.class)
+@Target({ElementType.FIELD})
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Conditional {
+
+  /**
+   * @return the 'name' of a sibling property to asserted
+   */
+  public String ifProperty();
+
+  /**
+   * @return the 'value' to assert on the field
+   */
+  public String[] hasConst();
+
+  @Retention(RetentionPolicy.RUNTIME)
+  @Target({ElementType.FIELD})
+  @interface List {
+      Conditional[] value();
+  }
+
+}

jsonschema-module-expressive-annotations/src/main/java/io/github/axonivy/json/schema/impl/ConditionalFieldProvider.java

@@ -22,6 +22,7 @@
 import com.github.victools.jsonschema.generator.SchemaVersion;
 
 import io.github.axonivy.json.schema.annotations.Condition;
+import io.github.axonivy.json.schema.annotations.Conditional;
 
 public class ConditionalFieldProvider implements CustomDefinitionProviderV2 {
 
@@ -44,26 +45,39 @@ public CustomDefinition provideCustomSchemaDefinition(ResolvedType javaType, Sch
   }
 
   private void annotate(ConditionBuilder builder, ResolvedField field) {
-    Consumer<Condition> add = condition -> builder.addCondition(condition, field.getName());
     Annotations annotations = field.getAnnotations();
-    Condition single = field.get(Condition.class);
-    if (single != null) {
-      add.accept(single);
+
+    Consumer<Condition> add = condition -> builder.addCondition(condition, field.getName());
+    Condition condition = field.get(Condition.class);
+    if (condition != null) {
+      add.accept(condition);
     }
     Condition.List conditions = annotations.get(Condition.List.class);
     if (conditions != null) {
       Arrays.stream(conditions.value()).forEachOrdered(add);
     }
+
+    Consumer<Conditional> addConditional = c -> builder.addConditional(c, field);
+    Conditional conditional = field.get(Conditional.class);
+    if (conditional != null) {
+      addConditional.accept(conditional);
+    }
+    Conditional.List conditionals = annotations.get(Conditional.List.class);
+    if (conditionals != null) {
+      Arrays.stream(conditionals.value()).forEachOrdered(addConditional);
+    }
   }
 
   public static class ConditionBuilder {
 
     private final SchemaVersion version;
     private final List<ObjectNode> conditions = new ArrayList<>();
     private DynamicRefs refs = new DynamicRefs();
+    private SchemaGenerationContext context;
 
     public ConditionBuilder(SchemaGenerationContext context) {
       this.version = context.getGeneratorConfig().getSchemaVersion();
+      this.context = context;
     }
 
     public ConditionBuilder refs(DynamicRefs resolver) {
@@ -78,6 +92,11 @@ public ObjectNode addCondition(Condition condition, String field) {
       return addCondition(field, condition.ifConst(), condition.thenProperty(), ref);
     }
 
+    public ObjectNode addConditional(Conditional condition, ResolvedField field) {
+      var resolved = context.createStandardDefinitionReference(field.getType(), null);
+      return addCondition(condition.ifProperty(), condition.hasConst(), field.getName(), resolved);
+    }
+
     public ObjectNode addCondition(String field, String expect, String thenProp, JsonNode thenRef) {
       return addCondition(field, new String[] {expect}, thenProp, thenRef);
     }

jsonschema-module-expressive-annotations/src/test/java/io/github/axonivy/json/schema/tests/TestFieldCondition.java

@@ -12,6 +12,7 @@
 import com.fasterxml.jackson.databind.node.ObjectNode;
 
 import io.github.axonivy.json.schema.annotations.Condition;
+import io.github.axonivy.json.schema.annotations.Conditional;
 
 class TestFieldCondition {
 
@@ -61,7 +62,6 @@ static class MyMultiConditionalField {
   @Test
   void multiple_constsToVerfiy() {
     ObjectNode schema = new ExpressiveSchemaGenerator().generateSchema(MyAnyOfConditionalField.class);
-    System.out.println(schema.toPrettyString());
 
     JsonNode provider = schema.get("if").get("properties").get("provider");
     var anyOf = provider.get("anyOf");
@@ -89,4 +89,76 @@ public static class ComplexType {
     }
   }
 
+  @Test
+  void conditionalOtherProp() {
+    ObjectNode schema = new ExpressiveSchemaGenerator().generateSchema(MyConditionalFieldSibling.class);
+
+    JsonNode ifProvider = schema.get("if").get("properties").get("provider");
+    assertThat(ifProvider.get("const").asText())
+      .isEqualTo("azure");
+
+    JsonNode thenProperty = schema.get("then").get("properties").get("always");
+    assertThat(thenProperty.get("$ref").asText())
+      .isEqualTo("#/$defs/ComplexType");
+  }
+
+  static class MyConditionalFieldSibling {
+    public String $schema; // self-ref
+
+    public String provider;
+
+    @Conditional(ifProperty = "provider", hasConst = { "azure" })
+    public ComplexType always;
+
+    public static class ComplexType {
+      public String name;
+    }
+  }
+
+  @Test
+  void conditionAndConditionalOtherProp() {
+    ObjectNode schema = new ExpressiveSchemaGenerator().generateSchema(MyMixedCondition.class);
+
+    var allOf = (ArrayNode)schema.get("allOf");
+    assertThat(allOf)
+      .as("multiple kinds of conditionals as one 'allOf' condition")
+      .isInstanceOf(ArrayNode.class);
+
+    JsonNode first = allOf.get(0);
+    JsonNode ifProvider = first.get("if").get("properties").get("provider");
+    assertThat(ifProvider.get("const").asText())
+      .isEqualTo("ms-ad");
+    JsonNode thenProperty = first.get("then").get("properties").get("ifAd");
+    assertThat(thenProperty.get("$ref").asText())
+      .isEqualTo("#/$defs/ComplexType");
+
+    JsonNode second = allOf.get(1);
+    JsonNode ifOther = second.get("if").get("properties").get("provider");
+    assertThat(ifOther.get("const").asText())
+      .isEqualTo("azure");
+    JsonNode thenThis = second.get("then").get("properties").get("ifAzure");
+    assertThat(thenThis.get("$ref").asText())
+      .isEqualTo("#/$defs/AzureType");
+  }
+
+  static class MyMixedCondition {
+    public String $schema; // self-ref
+
+    @Condition(ifConst  = { "ms-ad" }, thenProperty = "ifAd", thenRef = "#/$defs/ComplexType")
+    public String provider;
+
+    @Conditional(ifProperty = "provider", hasConst = { "azure" })
+    public AzureType ifAzure;
+
+    public static class AzureType {
+      public String id;
+    }
+
+    public ComplexType always;
+
+    public static class ComplexType {
+      public String name;
+    }
+  }
+
 }