🕷️ Patch tracking element load failure

[JFWooten4]

Docusaurus does not have a good time right now where there are interruptions between it and the Google Tag Manager. This PR stops the following recurring error (scales with page reloads when it happens):

Changes

Adds a runtime guard around Docusaurus’ Google gtag page-view tracking callback. It is often blocked by an ad blocker, delayed, or not loaded yet, that call can crash.

Previously, the plugin assumed window.gtag was always available before sending the page_view event. This patch returns early when window.gtag is not a function, preventing runtime errors in environments where the analytics script is unavailable.

The intent is to keep analytics optional and non-blocking, so page navigation continues safely even when Google tracking cannot run. Hence the page-view guard.

[Copilot]

Pull request overview

This PR makes Docusaurus’ Google gtag page-view tracking resilient to cases where window.gtag is blocked or not yet loaded (e.g., ad blockers / interrupted GTM), preventing runtime errors during navigation.

Changes:

• Adds a runtime guard to return early when window.gtag is not a function before sending page_view.

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[ElliotFriend]

The bug is real — the gtag plugin calls window.gtag(...) unguarded in onRouteDidUpdate, so ad blockers that strip the gtag bootstrap throw on every SPA navigation — and your 3-line guard is the right idea.

I don't want to take it as a package patch, though. Patches freeze us to a plugin version and rot silently (the pnpm migration in #2493 already left this PR's patch-package file inert — it currently applies nothing, which is why CI is green). And this particular fix doesn't need one: we can put the guard in our own code instead.

Proposal: rework this as a Docusaurus client module in src/ (registered via clientModules in docusaurus.config.ts) that defines the standard no-op gtag stub when it's missing, e.g.:

if (typeof window !== 'undefined' && typeof window.gtag !== 'function') {
  window.dataLayer = window.dataLayer || [];
  window.gtag = function () {
    window.dataLayer.push(arguments);
  };
}

Client modules load at app bootstrap, before any route update fires, so the plugin's unguarded call always finds a function. Same fix, zero patches, survives every plugin upgrade untouched.

Separately, this is worth an upstream issue at facebook/docusaurus so the plugin guards its own call — you found it, you should file it, and I'm glad to co-sign. Want to rework this PR along those lines?