[cpp-ue4] Handled nullable by setting the required tag, effectively m…

…aking nullables optionals (even if they may be required in the spec). This is because there is no such concept as a value being nullable in C++, and this generator deals with values, not pointers. (OpenAPITools#18168)

Co-authored-by: Samuel Kahn <[email protected]>

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppUE4ClientCodegen.java

@@ -20,6 +20,10 @@
 import io.swagger.v3.oas.models.media.Schema;
 import org.openapitools.codegen.CodegenConstants;
 import org.openapitools.codegen.CodegenType;
+import org.openapitools.codegen.CodegenModel;
+import org.openapitools.codegen.CodegenParameter;
+import org.openapitools.codegen.CodegenProperty;
+import org.openapitools.codegen.CodegenResponse;
 import org.openapitools.codegen.SupportingFile;
 import org.openapitools.codegen.meta.GeneratorMetadata;
 import org.openapitools.codegen.meta.Stability;
@@ -246,6 +250,34 @@ public void setOptionalProjectFileFlag(boolean flag) {
         this.optionalProjectFileFlag = flag;
     }
 
+    // override to post-process any model properties
+    @Override
+    @SuppressWarnings("unused")
+    public void postProcessModelProperty(CodegenModel model, CodegenProperty property) {
+        super.postProcessModelProperty(model, property);
+        // Nullable will be handled as optional
+        property.required = !property.notRequiredOrIsNullable();
+    }
+
+    // override to post-process any response
+    @Override
+    @SuppressWarnings("unused")
+    public void postProcessResponseWithProperty(CodegenResponse response, CodegenProperty property) {
+        super.postProcessResponseWithProperty(response, property);
+        // Nullable will be handled as optional
+        property.required = !property.notRequiredOrIsNullable();
+    }
+
+    // override to post-process any parameters
+    @Override
+    @SuppressWarnings("unused")
+    public void postProcessParameter(CodegenParameter parameter) {
+        super.postProcessParameter(parameter);
+        // Nullable will be handled as optional
+        parameter.required = !parameter.notRequiredOrIsNullable();
+    }
+
+
     /**
      * Configures the type of generator.
      *

modules/openapi-generator/src/main/resources/cpp-ue4/helpers-header.mustache

@@ -448,18 +448,21 @@ inline bool TryGetJsonValue(const TSharedPtr<FJsonObject>& JsonObject, const FSt
 template<typename T>
 inline bool TryGetJsonValue(const TSharedPtr<FJsonObject>& JsonObject, const FString& Key, TOptional<T>& OptionalValue)
 {
-	if(JsonObject->HasField(Key))
+	const TSharedPtr<FJsonValue> JsonValue = JsonObject->TryGetField(Key);
+	if (JsonValue.IsValid() && !JsonValue->IsNull())
 	{
 		T Value;
-		if (TryGetJsonValue(JsonObject, Key, Value))
+		if (TryGetJsonValue(JsonValue, Value))
 		{
 			OptionalValue = Value;
 			return true;
 		}
 		else
 			return false;
 	}
-	return true; // Absence of optional value is not a parsing error
+	// Absence of optional value is not a parsing error.
+	// Nullable is handled like optional.
+	return true;
 }
 
 {{#cppNamespaceDeclarations}}