Intent to Deprecate: HTMLHtmlElement.manifest

[Philip Jägenstedt]

Primary eng (and PM) emails

phi...@opera.com

Summary

Remove the HTMLHtmlElement.manifest IDL attribute.

Motivation

The spec says: "The manifest attribute only has an effect during the early stages of document load. Changing the attribute dynamically thus has no effect (and thus, no DOM API is provided for this attribute)."

http://www.whatwg.org/specs/web-apps/current-work/multipage/semantics.html#the-html-element

Only Blink/WebKit supports the IDL attribute, at least in this basic test: http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=2939

Compatibility Risk

Getting and setting the attribute after HTMLHtmlElement::insertedByParser() has been called has no effect, so the appcache mechanism itself is not affected, but as always scripts could depend on the return type (string not undefined) and misbehave in unknown ways.

Also, the attribute could be used for feature testing appcache, in which case a pre-appcache codepath would be taken. That should usually mean that the cache doesn't work, but the worst case is always complete breakage of the site.

Alternative implementation suggestion for web developers

Use window.ApplicationCache for feature testing, getAttribute('manifest') to read the attribute, and don't bother setting the attribute at all, since it has no effect.

Usage information from UseCounter

http://www.chromestatus.com/metrics/feature/timeline/popularity/210

The counter is available in M33, and the top measurement to date is 0.0141%.

Entry on chromestatus.com and/or MDN

http://www.chromestatus.com/features/6192449487634432 is Application Cache, to which this is related.

Requesting approval to remove too?

No, deprecate now and wait until after the next branch point before removing.

[PhistucK]

Can someone gather the Android specific numbers for this feature?

☆PhistucK

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[Jochen Eisinger]

For Android, it's below 0.01%, so LGTM to remove

[Eric Seidel]

For context, that's about twice as much usage as showModalDialog.
Although it's still below our 0.06% historical recommendation.

Why does usage look like it's increasing and work-day focused?
http://www.chromestatus.com/metrics/feature/timeline/popularity/210

In any case, LGTM to deprecate.