Include sizes attribute when parsing rel microformats.

[Zegnat]

When parsing a hyperlink element for rel microformats a number of possible attributes are added to the resulting object: hreflang, media, title, and type. This covers a lot of the possible attributes on <link> elements, especially those holding important meta data about the resource.

One attribute that is missing from this list is sizes. This becomes especially important when looking at rel="icon". When I was doing a survey on logo metadata for IndieAuth clients a microformats2 parser would simply tell me it had found 3 rel="icon" links on indielogin.com. It would be impossible to select the right one without the sizes data.

Proposed spec change:

With the current list of attributes to check under:

• add keys to the hash of the key with name url for each of these attributes (if present) and key not already set:

Add the sub item:

• "sizes": the value of the "sizes" attribute

[Zegnat]

There was some discussion about this issue in the chat, starting here (my response the next day). This concerned the use of rel="icon" in combination with IndieAuth client information discovery. I want to make clear that this issue is purely about the usefulness of the rel parser, separate of whatever way IndieAuth chooses to go.

And as @kevinmarks said:

• If sizes is important we should consider adding it to rel parsing - we added only attributes we saw in the wild.

Not only are we seeing the attribute in the wild, it is a clearly defined in the HTML spec now (which it probably wasn’t back when the first list of attributes was decided on). It is also important because the output of the rel parser for pages publishing multiple rel="icon"s becomes useless when they are only differentiable by the (missing) sizes attribute.

My reasoning is much as described by @sknebel:

• […] all reasonably widely accepted link-rel-attributes should be covered by the parsers, since it's a very easy addition to the parser and the effort for the parser users that might want a rel-parser too to add another parsing thing just to see the properties the microformats parser doesn't cover is pretty annoying in comparison

I hope that clears things up!