Fix rendering of OpenAPI nullable defined with allOf. (#1033)

.changeset/chatty-balloons-approve.md

@@ -0,0 +1,5 @@
+---
+"fumadocs-openapi": patch
+---
+
+Fix rendering of OpenAPI nullable defined with `allOf`.

packages/openapi/src/render/schema.tsx

@@ -71,7 +71,11 @@ export function Schema({
   const child: ReactNode[] = [];
 
   // object type
-  if (isObject(schema) && parseObject) {
+  if (
+    isObject(schema) &&
+    parseObject &&
+    (schema.additionalProperties || schema.properties)
+  ) {
     const { additionalProperties, properties } = schema;
 
     if (additionalProperties === true) {
@@ -249,10 +253,21 @@ function getSchemaType(schema: OpenAPI.SchemaObject, ctx: Context): string {
       .map((one) => getSchemaType(noRef(one), ctx))
       .join(' | ');
 
-  if (schema.allOf)
-    return schema.allOf
-      .map((one) => getSchemaType(noRef(one), ctx))
-      .join(' & ');
+  if (schema.allOf) {
+    const allTypeNames = schema.allOf.map((one) =>
+      getSchemaType(noRef(one), ctx),
+    );
+    const hasNull = allTypeNames.includes('null');
+    const nonNullTypes = allTypeNames.filter((v) => v !== 'null');
+    const nonNullTypeNames = nonNullTypes.join(' & ');
+
+    if (!hasNull) return nonNullTypeNames;
+
+    if (nonNullTypes.length === 0) return 'null';
+    else if (nonNullTypes.length === 1 || !hasNull)
+      return `${nonNullTypeNames} | null`;
+    else return `(${nonNullTypeNames}) | null`;
+  }
 
   if (schema.not) return `not ${getSchemaType(noRef(schema.not), ctx)}`;
 

packages/openapi/src/utils/combine-schema.ts

@@ -8,10 +8,14 @@ export function combineSchema(
   schema: OpenAPI.SchemaObject[],
 ): OpenAPI.SchemaObject {
   const result: OpenAPI.SchemaObject = {
-    type: 'object',
+    type: undefined,
   };
 
   function add(s: OpenAPI.SchemaObject): void {
+    if (s.type) {
+      result.type = result.type ? 'object' : s.type;
+    }
+
     if (s.properties) {
       result.properties ??= {};
       Object.assign(result.properties, s.properties);
@@ -32,6 +36,15 @@ export function combineSchema(
       result.required.push(...s.required);
     }
 
+    if (s.enum && s.enum.length > 0) {
+      result.enum ??= [];
+      result.enum.push(...s.enum);
+    }
+
+    if (s.nullable) {
+      result.nullable = true;
+    }
+
     if (s.allOf) {
       noRef(s.allOf).forEach(add);
     }