[DEFECT] SDK: Page Query Override Breaks Contentlet Data When Extending Page Response

Problem Statement

When developers pass a custom page GraphQL fragment to extend the page response (e.g. to fetch relationships like author { firstName }), the SDK currently disables _map for contentlets unless manually re-added.

This causes missing contentlet fields in the UI and forces developers to reconstruct internal query fragments.

This behavior was intentional originally (full override mode), but real usage shows most developers only want to extend the response; not replace core fields.

We need to evaluate the best long-term solution.

Steps to Reproduce

If you try this request:

dotCMSClient.page.get(path, {
  graphql: {
    page: `
      urlContentMap {
        ... on Blog {
          author {
            firstName
          }
        }
      }
    `
  }
});

Your page will be broken; to fix it to need to do:

page: `
  containers {
    containerContentlets {
      contentlets { _map }
    }
  }
  urlContentMap {
    ... on Blog {
      author { firstName }
    }
  }
`

Video

https://github.com/user-attachments/assets/5ed71424-0a9f-484b-8da1-4ca6c1a383fa

Acceptance Criteria

Acceptance Criteria for Spike

• Written proposal with recommended approach
• Code experiment or prototype (if needed)
• Impact analysis (DX, backwards compatibility, performance)
• Next steps: implement ticket OR technical design doc

dotCMS Version

@dotcms/client@latest

Severity

Medium - Some functionality impacted

Start with the dotCMSClient.page.get reproduction and compare the custom page GraphQL fragment with the version that explicitly includes containers, containerContentlets, contentlets, and _map. Assess the behavior's DX, backwards-compatibility, and performance impact, then document a recommended approach, prototype if needed, and next steps as requested by the spike acceptance criteria.