Fix script tag replacer

[puntope]

Changes proposed in this Pull Request:

Closes #279

Checks:

• Does your code follow the WordPress coding standards?
• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Detailed test instructions:

1. Dont check out this PR and create this filter

add_filter( 'script_loader_tag', array( $this, 'change_script_tags' ), 1, 3 );
function change_script_tags( $tag, $handle, $src ) {
		if ( in_array( $handle, self::ASYNC_SCRIPT_HANDLES, true ) ) {
			$tag = '<script type="text/javascript" src="' . $src . '" id="' . $handle . '-js"></script>';
		}
		return $tag;
	}

2. Go to the Shop and search for google-tag-manager script in the source
3. See "async" attribute not being added
4. Checkout this PR
5. Refresh
6. See "async" attribute being added

Additional details:

Changelog entry

Fix - Add async attribute in google-tag-manager script.

[eason9487]

Thanks for the fix.

This is not a blocker, but it would be a bit better to avoid having two async attributes, even though it won't cause any real problems. (One of the async attributes seems to come from WC-Blocks)

[puntope]

Howdy @eason9487 thanks for that catch. Might you test again with this change f571294 ?

Thanks

[eason9487]

Two async attributes still occur as this regex pattern cannot match correctly. Maybe consider matching it with a pattern like /\basync\b/?

See #287 (comment)

[puntope]

Thanks @eason9487, for me it seems like working in Firefox and Chrome... but I replaced it with your solution here e3dd72c

Can you check one more time?
Thanks

[eason9487]

Thanks for the fix. LGTM.

for me it seems like working in Firefox and Chrome... [...]

Not sure what makes them different. In my testing env, the $tag content includes two script tags at a time and is separated by a linebreak char as the following, so the previous regex pattern couldn't match.

<script async src='https://www.googletagmanager.com/gtag/js?id=G-XXXXXXXXXX' id='google-tag-manager-js'></script>
<script id='google-tag-manager-js-after'>
	window.dataLayer = window.dataLayer || [];
	function gtag(){dataLayer.push(arguments);}
	gtag('js', new Date());
	gtag('config', 'G-XXXXXXXXXX', { 'send_page_view': false });
</script>