Allow empty structs and all optionals in Generatable

Sources/LLMMacrosImplementation/GeneratableMacro.swift

@@ -33,12 +33,15 @@ public struct GeneratableMacro: MemberMacro, ExtensionMacro {
             let schemaExpr = schema(for: unwrappedType, in: declaration, context: context)
             return (name, schemaExpr, !isOptional)
         }
+        let emptyStringToken="\"\""
         let propertyExprsString = props.map { "\"\\\"" + $0.name + "\\\": \" + " + $0.schema }.joined(separator: " + \",\" + ")
+        let propertyExprsStringFinal = propertyExprsString.isEmpty ? emptyStringToken : propertyExprsString
         let requiredExprString = props.filter { $0.isRequired }.map { "\"\\\"" + $0.name + "\\\"\"" }.joined(separator: " + \",\" + ")
+        let requiredExprStringFinal = requiredExprString.isEmpty ? emptyStringToken : requiredExprString
         return [
             """
             public static var jsonSchema: String {
-                return "{ \\"type\\": \\"object\\", \\"properties\\": {" + \(raw: propertyExprsString) + "}, \\"required\\": [" + \(raw: requiredExprString) + "] }"
+                return "{ \\"type\\": \\"object\\", \\"properties\\": {" + \(raw: propertyExprsStringFinal) + "}, \\"required\\": [" + \(raw: requiredExprStringFinal) + "] }"
             }
             """
         ]
@@ -149,4 +152,4 @@ enum MacroError: Error, CustomStringConvertible {
         case .notAStruct: "Can only be applied to a struct."
         }
     }
-} 
+} 

Tests/LLMTests/LLMTests.swift

@@ -779,4 +779,56 @@ final class LLMTests {
         #expect(assignee["name"] is String)
         #expect(assignee["age"] is Int)
     }
+
+    @Generatable
+    struct EmptyTestStruct { }
+
+    @Test
+    func testEmptyGeneratable() async throws {
+        let bot = try await LLM(from: model)!
+
+        let result = try await bot.respond(
+            to: "Create the void",
+            as: EmptyTestStruct.self
+        )
+        let project = result.value
+        let output = result.rawOutput
+
+        print("Project: \(project)")
+        print("Raw output: \(output)")
+
+        let jsonData = output.data(using: String.Encoding.utf8)!
+        let parsed = try JSONSerialization.jsonObject(with: jsonData) as! [String: Any]
+        #expect(parsed.isEmpty)
+    }
+
+    @Generatable
+    struct AllNullableAttributes {
+        let first: Int?
+        let second: Int?
+    }
+
+    @Test
+    func testStructWithNullableAttributes() async throws {
+        let bot = try await LLM(from: model)!
+
+        print(AllNullableAttributes.jsonSchema)
+
+        // Note: it seems it is hard to tell this LLM to return an empty JSON or drop an attribute,
+        // so stick to just simple type checking
+        let result = try await bot.respond(
+            to: "Return something",
+            as: AllNullableAttributes.self
+        )
+        let project = result.value
+        let output = result.rawOutput
+
+        print("Project: \(project)")
+        print("Raw output: \(output)")
+
+        let jsonData = output.data(using: String.Encoding.utf8)!
+        let parsed = try JSONSerialization.jsonObject(with: jsonData) as! [String: Any]
+        #expect(parsed["first"] is Int?)
+        #expect(parsed["second"] is Int?)
+    }
 }