Fix: honor nullable: true on object types with additionalProperties

changelog.md

@@ -59,3 +59,7 @@ A major release with breaking changes. Involves updating type signatures to matc
 ### 3.5.4
 
 - Fix for @tanstack/query v5.89.0 onError, onSuccess and onSettled signature change referenced in issue 9660
+
+### 3.5.5
+
+- Fix `nullable: true` not being honored for `object` types with `additionalProperties` (dictionary types). Both code paths in `src/common/util.ts` now wrap the dictionary type with `appendNullToUnion` so `| null` is appended when `nullable: true` is set.

spec/common/types.spec.ts

@@ -70,6 +70,12 @@ export type MyDictionaryValueNested = {
         };
     };
 };
+export type MyNullableDictionary = {
+    [key: string]: any;
+} | null;
+export type MyNullableDictionaryString = {
+    [key: string]: string;
+} | null;
 `;
 
 describe("makeTypes", () => {
@@ -293,6 +299,18 @@ describe("makeTypes", () => {
               },
             },
           },
+          MyNullableDictionary: {
+            type: "object",
+            additionalProperties: true,
+            nullable: true,
+          },
+          MyNullableDictionaryString: {
+            type: "object",
+            additionalProperties: {
+              type: "string",
+            },
+            nullable: true,
+          },
         },
       },
     };

src/common/util.ts

@@ -137,7 +137,7 @@ export function schemaObjectTypeNode(
   }
 
   if (item.additionalProperties) {
-    return createDictionaryType($refs, item);
+    return appendNullToUnion(createDictionaryType($refs, item), item.nullable);
   }
 
   if (item.properties) {
@@ -253,7 +253,10 @@ export function nonArraySchemaObjectTypeToTs(
       );
     case "object": {
       if (item.additionalProperties) {
-        return createDictionaryType($refs, item);
+        return appendNullToUnion(
+          createDictionaryType($refs, item),
+          item.nullable
+        );
       }
 
       return appendNullToUnion(