From f737be39bc26c101cf5087bd0df5037021ee3a74 Mon Sep 17 00:00:00 2001
From: worstell <worstell@squareup.com>
Date: Tue, 14 Nov 2023 10:32:39 -0800
Subject: [PATCH] fix(kotlin): allow empty return types (#594)

---
 .../xyz/block/ftl/schemaextractor/ExtractSchemaRule.kt      | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kotlin-runtime/ftl-runtime/src/main/kotlin/xyz/block/ftl/schemaextractor/ExtractSchemaRule.kt b/kotlin-runtime/ftl-runtime/src/main/kotlin/xyz/block/ftl/schemaextractor/ExtractSchemaRule.kt
index 2d89ff7654..113c854120 100644
--- a/kotlin-runtime/ftl-runtime/src/main/kotlin/xyz/block/ftl/schemaextractor/ExtractSchemaRule.kt
+++ b/kotlin-runtime/ftl-runtime/src/main/kotlin/xyz/block/ftl/schemaextractor/ExtractSchemaRule.kt
@@ -142,9 +142,11 @@ class SchemaExtractor(
       }
 
       // Validate return type
-      val respClass = verb.createTypeBindingForReturnType(bindingContext)?.type?.toClassDescriptor()
+      val respClass = verb.createTypeBindingForReturnType(bindingContext)?.type
         ?: throw IllegalStateException("Could not resolve ${verb.name} return type")
-      require(respClass.isData) { "Return type of ${verb.name} must be a data class" }
+      require(respClass.toClassDescriptor().isData || respClass.isEmptyClassTypeAlias()) {
+        "Return type of ${verb.name} must be a data class or typealias of Unit"
+      }
     }
   }