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# Diagnostics Developer-mode warnings and error reporting. This module powers the feedback you get while developing: `[PN] WARN` messages for suspicious props and styles, the [`HookOrderError`][pythonnative.HookOrderError] raised on conditional hooks, and the RedBox overlay that surfaces uncaught errors from renders, effects, and event handlers. Dev mode is enabled automatically by `pn start` / `pn preview` and in the debug builds `pn run` produces, or explicitly with the `PN_DEV=1` environment variable. In production builds every check in this module is skipped, so shipping apps pay no overhead. ```python import pythonnative as pn if pn.diagnostics.is_dev(): pn.diagnostics.warn("fetching from a staging endpoint") ``` Most apps never call this module directly; it exists so framework code (and custom component libraries) can report problems in a way that reaches the developer instead of disappearing into a log. ::: pythonnative.diagnostics options: show_root_heading: false show_root_toc_entry: false members_order: source filters: ["!^_"] ## Next steps - Catch render errors in the tree with [`ErrorBoundary`][pythonnative.ErrorBoundary]: see the [Error boundaries guide](../guides/error-boundaries.md). - The rules of hooks and what `HookOrderError` means: [Hooks](../concepts/hooks.md).