🐛 Prevent duplicate Next.js RUM views from discarded renders

[BeltranBulbarellaDD]

Motivation

Fixes #4931, where DatadogAppRouter and DatadogPagesRouter could call startNextjsView() during a render that React later discarded. Because the render-phase useRef guard is recreated for discarded fibers, those calls could create duplicate RUM views.

Changes

• Move the shared view-start logic into useStartNextjsView, which calls startNextjsView() from useLayoutEffect after the render commits.
• Reuse the hook in both App Router and Pages Router integrations while preserving route-pattern view names and concrete-path navigation detection.
• Wait for the Pages Router to be ready before starting the initial view.
• Add unit tests for Strict Mode, route changes, and router readiness.
• Add an end-to-end regression test covering a discarded App Router render.

Test instructions

• Run the Next.js router unit tests.
• Run the Next.js plugin E2E scenario, including should not create a view for a discarded App Router render.

Checklist

• Added unit tests for this change.
• Added e2e/integration tests for this change.
• Tested locally
• Tested on staging
• Updated documentation and/or relevant AGENTS.md file

[datadog-datadog-prod-us1]

 

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ℹ️ Info

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