fix($plugin-google-analytics): duplicate tracking of first page (fix #2017)

[ajitzero]

Fixes #2017
Reasoning in Issue.

[meteorlxy]

Thanks for your contribution, but please do not delete the PR template next time.

I found another issue, and it would be better if we can solve it, too.

Scene 1

Open the homepage: https://deploy-preview-2039--vuepress.netlify.com/

Click "Get Started" (i.e. go to the guide page via vue-router):

dl param is wrong

Scene 2

Open the guide page directly: https://deploy-preview-2039--vuepress.netlify.com/guide/

dl param is correct

Conclusion

dl param is always pointing to the "previous" page.

Notice that dp param is useless here according to GA Docs, because we don't have a dh param together

[ajitzero]

I just checked it out.

dl param is always pointing to the "previous" page.

I tried opening other pages and switching multiple times. It's actually always pointing to the first page (whichever it may be) that we open. Only the dp changes at each router change.

The way it is currently written, the valid URL per route is the base URL (/ or ) + dp, concatenated. I'll look into the docs and get back to you shortly.

[ajitzero]

@meteorlxy This seems to be the intended behavior to track the point of entry, after which the dp param holds the consequent path. This is not a bug, as it is. We will need to check the GA results (dashboard) for any inconsistencies.

[meteorlxy]

@ajitzero

Hmmmm that's strange.

For 'pageview' hits, either &dl or both &dh and &dp have to be specified for the hit to be valid

But there is no dh to work together.

It seems that the behavior of "analytics.js" is not consistent with the documentation of "Measurement Protocol".

Alright, let's put this issue aside and merge this PR first.

Thanks for your contribution and investigation ❤️

[meteorlxy]

Oh fuck, wrong scope 😅 ....

[vue-bot]

Thanks again! 💚

[ajitzero]

Glad I could contribute! Thank you 😇