Catalog Backend Module to resolve $refs in yaml documents

This is an extension module to the Catalog backend, providing extensions to resolve $refs in yaml documents.

With this you can split your yaml documents into multiple files and reference them. They will be bundled, using an UrlReader, during processing and stored as a single specification.

This is useful for OpenAPI and AsyncAPI specifications.

Installation

Install the package

# From your Backstage root directory
yarn --cwd packages/backend add @backstage/plugin-catalog-backend-module-openapi
Copy

Adding the plugin to your packages/backend

backend.add(import('@backstage/plugin-catalog-backend-module-openapi'));
Copy

This will add the jsonSchemaRefPlaceholderResolver for the placeholder resolver keys asyncapi and openapi.

This allows you to use the $openapi placeholder when referencing your OpenAPI specification and $asyncapi when referencing your AsyncAPI specifications. This will then resolve all $ref instances in your specification.

You can also use this resolver for other kind of yaml files to resolve $ref pointer.

apiVersion: backstage.io/v1alpha1
kind: API
metadata:
  name: example
  description: Example API
spec:
  type: openapi
  lifecycle: production
  owner: team
  definition:
    $openapi: ./spec/openapi.yaml # by using $openapi Backstage will now resolve all $ref instances
Copy

Adding the plugin to your packages/backend (old backend system)

jsonSchemaRefPlaceholderResolver

The placeholder resolver can be added by importing jsonSchemaRefPlaceholderResolver in src/plugins/catalog.ts in your backend package and adding the following.

builder.setPlaceholderResolver('openapi', jsonSchemaRefPlaceholderResolver);
builder.setPlaceholderResolver('asyncapi', jsonSchemaRefPlaceholderResolver);
Copy

This allows you to use the $openapi placeholder when referencing your OpenAPI specification and $asyncapi when referencing your AsyncAPI specifications. This will then resolve all $ref instances in your specification.

You can also use this resolver for other kind of yaml files to resolve $ref pointer.

apiVersion: backstage.io/v1alpha1
kind: API
metadata:
  name: example
  description: Example API
spec:
  type: openapi
  lifecycle: production
  owner: team
  definition:
    $openapi: ./spec/openapi.yaml # by using $openapi Backstage will now resolve all $ref instances
Copy

OpenAPIRefProcessor (deprecated)

The processor can be added by importing OpenApiRefProcessor in src/plugins/catalog.ts in your backend package and adding the following.

builder.addProcessor(
  OpenApiRefProcessor.fromConfig(env.config, {
    logger: env.logger,
    reader: env.reader,
  }),
);
Copy