[🐞]: forwarding gtm dataLayer.push breaks immediate dataLayer pushes

[DzmVasileusky]

Describe the bug

Partytown and GTM integration docs page says we should add dataLayer.push to the forward array.
But after doing it immediate call of dataLayer.push stops to work.

index.html

        <script src="/head-scripts/partytown.config.js"></script>
        <script src="/~partytown/debug/partytown.js"></script>
        <script>
            if (!navigator.isServer) {
                (function (w, d, s, l, i) {
                    w[l] = w[l] || [];
                    w[l].push({ 'gtm.start': new Date().getTime(), event: 'gtm.js' });
                    var f = d.getElementsByTagName(s)[0],
                        j = d.createElement(s),
                        dl = l !== 'dataLayer' ? '&l=' + l : '';
                    j.type = 'text/javascript';
                    j.async = true;
                    j.src = 'https://www.googletagmanager.com/gtm.js?id=' + i + dl;
                    f.parentNode.insertBefore(j, f);
                })(window, document, 'script', 'dataLayer', '#gtmAccountId#');

                // Immediate call of dataLayer.push which is working if not forwarded
                window.dataLayer = window.dataLayer || [];
                window.dataLayer.push({
                    partyTownEnabled: true,
                    event: 'Partytown_ready'
                });
            }
        </script>

/head-scripts/partytown.config.js

partytown = (function () {
    const FORWARD_LIST = [
        'dataLayer.push'
    ];
    return {
        forward: FORWARD_LIST
    };
})();

If I am removing it from forwarded list - it works like a charm.

Reproduction

https://tp8h37-5000.csb.app/

Steps to reproduce

1. Open the reproduction url.
2. Disabled Adblock, Ublock and other gtm blocking extensions
3. Open the console

Actual:
Only GTM started message is output

Expected:
GTM started and
Partytown enabled: true messages are output

Browser Info

Chrome

Additional Information

Not sure but maybe it is caused by this partytown code delete win[property.split(".")[0]];

[DzmVasileusky]

Actually adding defer to both partytown config and script solved the issue. But not sure if it is a good idea to defer partytown

[thekingbk90]

Although dataLayer.push isn't working in chrom console, most of data is pushed to gtag manager.
However we missed all data from mobile web, maybe partytown works only on desktop version?

[DzmVasileusky]

@thekingbk90 Not sure what case are you describing but it definitely doesn't send an event in my example.
I set up a testing project in gtm and tag was never triggered.

Setting 1000ms timeout or excluding it from forward makes it work. But my intention is to pass a feature flag to manage which gtm scripts should be handled by partytown