Consider supporting oEmbed for Tumblr sites on custom domains

[johnbillion]

Slack convo: ​https://wordpress.slack.com/archives/core/p1429065580004024

Tumblr sites on custom domains can't be embedded because their domains won't match our oEmbed whitelist.

Thought exercise: we could do a server-side request to the site (after it fails to match an oEmbed provider), detect the application/json+oembed link in the page, and if it includes the tumblr.com oEmbed endpoint then allow the URL to be embedded.

[dd32]

Personally I'm of the mind that not supporting custom domains is OK for now.

I do think that it's worthwhile thinking about how we could handle custom domains though, since Tumblr is not unique in this - other providers such as WordPress.com & Jetpack also use custom domains (It's worth noting, that we don't yet support WordPress.com's oEmbeds).

[johnbillion]

Related: #32522 (enables oEmbed link discovery)

[johnbillion]

Tumblr doesn't expose its oEmbed endpoint via discovery links in the header. I'm not sure if it's theme-dependent or not. If they did expose this, it would allow Tumblr sites on custom domains to be embedded now that discovery is enabled by default in core (see #32522).

@jkudish Does the WordPress.com partnership team have a contact at Tumblr they can mention this to?

[jkudish]

Hello,

Yes we do have a contact that I've reached out to with details about this ticket. I've asked him to reply here directly if possible, but otherwise I'll act as a relay.

Keep you posted if I hear back.

[ceyko]

I gave it a check, and tumblr does indeed expose oEmbed endpoints via discovery links. Here's an example from both a custom domain blog, and non:

$ curl -Ls "http://davidslog.com/post/128062418445" | grep oembed
<link rel="alternate" type="application/json+oembed" href="https://www.tumblr.com/oembed/1.0?url=http://www.davidslog.com/128062418445" title="..."/>

$ curl -Ls "http://staff.tumblr.com/post/128383384520" | grep oembed
<link rel="alternate" type="application/json+oembed" href="https://www.tumblr.com/oembed/1.0?url=http://staff.tumblr.com/post/128383384520" title=""/>

Do you have any examples from blogs where it is missing?

[johnbillion]

Replying to ceyko:

Do you have any examples from blogs where it is missing?

Yep, the discovery links aren't present on ​http://greatshowdowns.com/, which is a custom domain on Tumblr. Maybe it's related to the theme.

[johnbillion]

Wait, I'm an idiot. I was checking the home pages, not individual permalinks. The discovery links are indeed there.

curl -Ls "http://greatshowdowns.com/post/130695896684/jurassic-backs-new-print-debuting-at-nycc-this" | grep oembed
<link rel="alternate" type="application/json+oembed" href="https://www.tumblr.com/oembed/1.0?url=http://greatshowdowns.com/post/130695896684/jurassic-backs-new-print-debuting-at-nycc-this" title="[snip]"/>

[johnbillion]

Closing as wontfix in favour of #32522. Tumblr custom domains do indeed provide oEmbed discovery.

Thanks for the feedback, @ceyko!