feat: support non-map return values returned from Function Tools as in https://google.github.io/adk-docs/tools-custom/function-tools/#return-type

PiperOrigin-RevId: 838719814

Author: Mateusz Krawiec

core/src/main/java/com/google/adk/tools/FunctionTool.java

@@ -238,8 +238,15 @@ private Maybe<Map<String, Object>> call(Map<String, Object> args, ToolContext to
               data -> OBJECT_MAPPER.convertValue(data, new TypeReference<Map<String, Object>>() {}))
           .toMaybe();
     } else {
-      return Maybe.just(
-          OBJECT_MAPPER.convertValue(result, new TypeReference<Map<String, Object>>() {}));
+      try {
+        return Maybe.just(
+            OBJECT_MAPPER.convertValue(result, new TypeReference<Map<String, Object>>() {}));
+      } catch (IllegalArgumentException e) {
+        // Conversion to map failed, in this case we follow
+        // https://google.github.io/adk-docs/tools-custom/function-tools/#return-type and return
+        // the { "result": $result }
+        return Maybe.just(ImmutableMap.of("result", result));
+      }
     }
   }
 

core/src/test/java/com/google/adk/tools/FunctionToolTest.java

@@ -328,6 +328,15 @@ public void call_withPojoParamWithFields() throws Exception {
     assertThat(result).containsExactly("field1", "abc", "field2", 123);
   }
 
+  @Test
+  public void call_withBooleanReturnValue_returnsMapWithResult() throws Exception {
+    FunctionTool tool = FunctionTool.create(Functions.class, "returnsBoolean");
+
+    Map<String, Object> result = tool.runAsync(ImmutableMap.of(), null).blockingGet();
+
+    assertThat(result).containsExactly("result", true);
+  }
+
   @Test
   public void call_withPojoParamWithGettersAndSetters() throws Exception {
     FunctionTool tool = FunctionTool.create(Functions.class, "pojoParamWithGettersAndSetters");
@@ -894,6 +903,10 @@ public static Single<Map<String, Object>> returnsSingleMap() {
       return Single.just(ImmutableMap.of("key", "value"));
     }
 
+    public static Boolean returnsBoolean() {
+      return true;
+    }
+
     public static PojoWithGettersAndSetters returnsPojo() {
       PojoWithGettersAndSetters pojo = new PojoWithGettersAndSetters();
       pojo.setField1("abc");