Intent to Ship: Move location.fragmentDirective to document.fragmentDirective

[David Bokan]

***This is a minor change to the already shipped (in M80) text-fragment feature. I followed the chromestatus intent template which asks for many links - where not specific or relevant to this change I point at the general text-fragment feature.***

Contact emails

bo...@chromium.org

Explainer

https://crbug.com/1057795
https://github.com/whatwg/html/issues/5523

Specification

https://wicg.github.io/scroll-to-text-fragment/#feature-detectability

Design docs

https://github.com/WICG/scroll-to-text-fragment/

TAG review

https://github.com/w3ctag/design-reviews/issues/392

Summary

This is a small change to the text-fragments feature in https://chromestatus.com/feature/4733392803332096. The above introduced an empty object at `window.location.fragmentDirective` as a means to feature detect the newly added text-fragment capability. `window.location` turns out to be a bad place for this functionality, see https://crbug.com/1057795. This change moves `window.location.fragmentDirective` to `document.fragmentDirective` which seems like a more appropriate and safer place.

Link to “Intent to Prototype” blink-dev discussion

https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/aKI6doxffgQ/7dzrVvo4CAAJ

Risks

Interoperability and Compatibility

Chromium is the only currently implementation of text-fragments so the interop risk is low. 

There is some compat risk that there are existing users of `window.location.fragmentDirective`, though this was only recently added in M80.

We added a use counter: https://chromestatus.com/metrics/feature/timeline/popularity/3283. This shows ~2% of page loads reading the field which seems high. An analysis of HTTPArchive shows ~4000 domains that read location.fragmentDirective: https://docs.google.com/spreadsheets/d/1WxHFozsnA4qwfbVdt0iKbuUyJfu6Z9aKdjqEC6sSGf4/edit?usp=sharing All these uses seem to be 2 analytics scripts from PayPal and PerimiterX that use it for user agent detection. Removing location.fragmentDirective doesn't appear to have a user visible effect on the page.

Gecko: No signal
WebKit: No signal
Web developers: No signals

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?

Yes

Is this feature fully tested by web-platform-tests?

Yes https://wpt.fyi/results/scroll-to-text-fragment/scroll-to-text-fragment-api.html?label=experimental&label=master&aligned

Tracking bug

https://crbug.com/1057795

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5679640498667520

This intent message was generated by Chrome Platform Status.

[Yoav Weiss]

LGTM1

This seems like a minor change required for compat, so better to go ahead with it now rather than later.

Please make sure that the public documentation of the feature and its detection (e.g. MDN, web.dev) is also changed to reflect the new feature detection method.

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[Thomas Steiner]

On Sat 8. Aug 2020 at 23:25 Yoav Weiss <yo...@yoav.ws> wrote:

LGTM1

This seems like a minor change required for compat, so better to go ahead with it now rather than later.

Please make sure that the public documentation of the feature and its detection (e.g. MDN, web.dev) is also changed to reflect the new feature detection method.

I’ve already taken care of web.dev: 

https://web.dev/text-fragments/#feature-detection

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[jd66...@gmail.com]

Enter code here...

[Mike West]

LGTM2.

[David Bokan]

Friendly ping. Still waiting on a third stamp here (and trying to make M86 cut this week)

[Chris Harrelson]

LGTM3

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[Thomas Steiner]

Now that this has landed, I have noticed that `window.FragmentDirective` (upper case 'F') is exposed, too, apart from `document.fragmentDirective` (before and after this shipment). Is this on purpose?

[David Bokan]

I think so, yes, and that's unchanged from before. `FragmentDirective` is the type for the object returned from `document.fragmentDirective`. I guess it gets added to the global object. This is consistent with other types, e.g. `window.Location`.

[Thomas Steiner]

On Wed, Sep 2, 2020 at 4:00 PM David Bokan <bo...@google.com> wrote:

I think so, yes, and that's unchanged from before. `FragmentDirective` is the type for the object returned from `document.fragmentDirective`. I guess it gets added to the global object. This is consistent with other types, e.g. `window.Location`.

Sounds good, thanks! For feature detection, it's probably still better to look for `document.fragmentDirective`. 

[jacob duncan]