feat: auto populate propertyOrdering in Schema builder and transformers

src/main/java/com/google/genai/Transformers.java

@@ -43,6 +43,8 @@
 import com.google.genai.types.VoiceConfig;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.Map;
 import java.util.List;
 import java.util.logging.Logger;
 import java.util.regex.Matcher;
@@ -221,14 +223,58 @@ public static Content tContent(Object content) {
 
   /** Transforms an object to a Schema for the API. */
   public static Schema tSchema(Object origin) {
+    Schema schema = null;
     if (origin == null) {
       return null;
     } else if (origin instanceof Schema) {
-      return (Schema) origin;
+      schema = (Schema) origin;
     } else if (origin instanceof JsonNode) {
-      return JsonSerializable.fromJsonNode((JsonNode) origin, Schema.class);
+      schema = JsonSerializable.fromJsonNode((JsonNode) origin, Schema.class);
+    } else {
+      throw new IllegalArgumentException("Unsupported schema type: " + origin.getClass());
+    }
+    return populatePropertyOrdering(schema);
+  }
+
+  private static Schema populatePropertyOrdering(Schema schema) {
+    if (schema == null) {
+      return null;
     }
-    throw new IllegalArgumentException("Unsupported schema type: " + origin.getClass());
+    Schema.Builder builder = schema.toBuilder();
+    boolean modified = false;
+
+    if (schema.properties().isPresent() && !schema.properties().get().isEmpty()) {
+      Map<String, Schema> updatedProperties = new LinkedHashMap<>();
+      boolean childModified = false;
+      for (Map.Entry<String, Schema> entry : schema.properties().get().entrySet()) {
+        Schema originalChild = entry.getValue();
+        Schema populatedChild = populatePropertyOrdering(originalChild);
+        if (populatedChild != originalChild) {
+          childModified = true;
+        }
+        updatedProperties.put(entry.getKey(), populatedChild);
+      }
+      if (childModified) {
+        builder.properties(updatedProperties);
+        modified = true;
+      }
+
+      if (!schema.propertyOrdering().isPresent() && schema.properties().get().size() > 1) {
+        builder.propertyOrdering(new ArrayList<>(schema.properties().get().keySet()));
+        modified = true;
+      }
+    }
+
+    if (schema.items().isPresent()) {
+      Schema originalItems = schema.items().get();
+      Schema populatedItems = populatePropertyOrdering(originalItems);
+      if (populatedItems != originalItems) {
+        builder.items(populatedItems);
+        modified = true;
+      }
+    }
+
+    return modified ? builder.build() : schema;
   }
 
   public static SpeechConfig tSpeechConfig(Object speechConfig) {

src/main/java/com/google/genai/types/Schema.java

@@ -26,10 +26,8 @@
 import com.google.auto.value.AutoValue;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.genai.JsonSerializable;
-import java.util.Arrays;
-import java.util.List;
-import java.util.Map;
-import java.util.Optional;
+
+import java.util.*;
 
 /**
  * Schema is used to define the format of input/output data.
@@ -698,7 +696,18 @@ public Builder type(String type) {
       return type(new Type(type));
     }
 
-    public abstract Schema build();
+    abstract Schema autoBuild();
+
+    abstract Optional<Map<String, Schema>> properties();
+
+    abstract Optional<List<String>> propertyOrdering();
+
+    public Schema build() {
+      if (!propertyOrdering().isPresent() && properties().isPresent() && properties().get().size() > 1) {
+        propertyOrdering(new ArrayList<>(properties().get().keySet()));
+      }
+      return autoBuild();
+    }
   }
 
   /** Deserializes a JSON string to a Schema object. */

src/test/java/com/google/genai/TransformersTest.java

@@ -25,6 +25,7 @@
 import com.fasterxml.jackson.databind.node.JsonNodeFactory;
 import com.fasterxml.jackson.databind.node.ObjectNode;
 import com.fasterxml.jackson.databind.node.TextNode;
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.genai.types.File;
 import com.google.genai.types.FunctionDeclaration;
@@ -126,6 +127,43 @@ public void testTSchema_Required_success() {
     assertEquals(schema, transformedSchema);
   }
 
+  @Test
+  public void testTSchema_PropertyOrdering_autoPopulated() {
+    Schema schema =
+        Schema.builder()
+            .type("OBJECT")
+            .properties(
+                ImmutableMap.of(
+                    "name", Schema.builder().type("STRING").build(),
+                    "age", Schema.builder().type("INTEGER").build()))
+            .build();
+
+    Schema transformedSchema = Transformers.tSchema(schema);
+    assertTrue(transformedSchema.propertyOrdering().isPresent());
+    assertEquals(
+        ImmutableList.of("name", "age"),
+        transformedSchema.propertyOrdering().get());
+  }
+
+  @Test
+  public void testTSchema_PropertyOrdering_preservedIfExplicit() {
+    Schema schema =
+        Schema.builder()
+            .type("OBJECT")
+            .properties(
+                ImmutableMap.of(
+                    "name", Schema.builder().type("STRING").build(),
+                    "age", Schema.builder().type("INTEGER").build()))
+            .propertyOrdering("age", "name")
+            .build();
+
+    Schema transformedSchema = Transformers.tSchema(schema);
+    assertTrue(transformedSchema.propertyOrdering().isPresent());
+    assertEquals(
+        ImmutableList.of("age", "name"),
+        transformedSchema.propertyOrdering().get());
+  }
+
   @Test
   public void testTTool_noFunctions_success() {
     Tool tool =