Fix description for allOf-inheriting child schemas

Fixes #2810

Author: marcelstoer

packages/elements-core/src/components/Docs/Model/Model.spec.tsx

@@ -135,6 +135,21 @@ describe('Model', () => {
     expect(textboxDescription).toHaveTextContent('example schema description');
   });
 
+  it('displays child description at top of doc for allOf-inheriting objects', async () => {
+    const desc = 'child schema description';
+    // allOf-inheriting properties from parent but having its own description
+    const allOfSchema: JSONSchema7 = {
+      allOf: [exampleSchema],
+      description: desc,
+    };
+    render(<Model data={allOfSchema} />);
+    const description = screen.queryAllByText(desc);
+    const textboxDescription = screen.getByRole('textbox');
+
+    expect(description).toHaveLength(1);
+    expect(textboxDescription).toHaveTextContent(desc);
+  });
+
   it('does not display description at top of doc for non-objects', async () => {
     render(<Model data={exampleStringSchema} />);
     const description = screen.queryByRole('textbox');

packages/elements-core/src/components/Docs/Model/Model.tsx

@@ -93,12 +93,13 @@ const ModelComponent: React.FC<ModelProps> = ({
 
   const description = (
     <VStack spacing={10}>
-      {data.description && data.type === 'object' && (
-        <Box pos="relative">
-          <MarkdownViewer role="textbox" markdown={data.description} />
-          <NodeAnnotation change={descriptionChanged} />
-        </Box>
-      )}
+      {data.description &&
+        (data.type === 'object' || (data.allOf || []).some(s => (s as JSONSchema7).type === 'object')) && (
+          <Box pos="relative">
+            <MarkdownViewer role="textbox" markdown={data.description} />
+            <NodeAnnotation change={descriptionChanged} />
+          </Box>
+        )}
 
       <NodeVendorExtensions data={data} />