${documentReferrer} is empty when document.referrer is “https://www.google.com/”

[mattrohland]

Looking through the AMP documentation (https://github.com/ampproject/amphtml/blob/master/spec/amp-var-substitutions.md#document-referrer) is appears that the ${documentReferrer} variable should reflect the JS document.referrer.

While ${documentReferrer} appears to return the correct value for other domains (like: www.twitter.com, t.co, linkedin.com, etc.) when the page's document.referrer value is "https://www.google.com/" ${documentReferrer} is empty.

I couldn't find any documentation indicating that the www.google.com domain carried any additional caveats. Is this a bug or expected behavior?

---

For some context, this behavior was observed after implementing the "adobeanalytics_nativeConfig" approach provided by Adobe: https://marketing.adobe.com/resources/help/en_US/sc/implement/accelerated-mobile-pages.html

[cramforce]

To @lannka while @zhouyx is out.

This is certainly not intended.

[lannka]

@mattrohland do you have a page that we can reproduce the issue?

[mattrohland]

It turns out that the documentation provided by Adobe was not followed precisely in our implementation (https://marketing.adobe.com/resources/help/en_US/sc/implement/accelerated-mobile-pages.html).

Stripping out a lot of the noise, the following code was in use in our implementation:

<amp-analytics type="adobeanalytics_nativeConfig">
    <script type="application/json">
        {
            "requests": {
                "base": "https://${host}",
                "iframeMessage": "${base}/amp/iframe.html?page-referrer=${documentReferrer}"
            },
            "vars": {
                "host": "www.example.com",
                "documentReferrer" : "{{meta.Referer}}"
            },
            "extraUrlParams": {}
        }
    </script>
</amp-analytics>

Inclusion of the vars.documentReferrer entry deviated from Adobe's documentation and appears to be the culprit. Once that extra value was removed referrals for "https://www.google.com/" started to work correctly.

"vars": {
-     "host": "www.example.com",
-     "documentReferrer" : "{{meta.Referer}}"
+     "host": "www.example.com"
},
"extraUrlParams": {

This was an implementation issue on our end not a bug in AMP.

[lannka]

@mattrohland since you get that far, it will be appreciated if you could file a bug against adobe folks :-)