Mastodon: Use Atom feeds instead of RSS ones

[Sylvhem]

Contrary to popular belief, RSS isn't a normalized file format but three different file formats:

• RDF Site Summary (RSS 0.9 and RSS 1.0)
• Rich Site Summary (RSS 0.91)
• Really Simple Syndication (RSS 2.0)

This three formats have been developed by different people and are all incompatibles with each others. Moreover, none of them have been the subject to a standardization process (although, RSS 2.0 have been developed by the RSS Advisory Board).
That's one of the reasons why the IETF created the Atom file format, twelve years ago, in a attempt to offer a standardized and extensible syndication format using XML.

Mastodon already use Atom feeds, since they are needed for OStatus compatibility. However, since those feeds include additional informations required by the OStatus protocol, they aren't actually compatible with the Atom's specification (see #7443) and are not feed readers friendly. To provide actual syndication feeds, RSS feeds were included #7259.
However, given that RSS isn't really standardized and not maintained anymore, I think it's probably better to add additional Atom feeds instead of RSS ones.

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• [x] I searched or browsed the repo’s other issues to ensure this is not a duplicate.

[nightpool]

What are the actual effects on end users for creating a second atom feed instead of using RSS? "it isn't really standardized and not maintained anymore" isn't a compelling reason to switch, to me. What does atom support that RSS doesn't? What feed readers support atom but not RSS?

[Sylvhem]

What does atom support that RSS doesn't?

In Mastodon's case, nothing I believe. But it's not about that. It's about participating in the global effort to help a deprecated file format to die.

What feed readers support atom but not RSS?

No one I can think of. But that's not going to change if people don't switch from RSS to Atom.

Besides, why should Mastodon support RSS 2.0 when it already support Atom?

[nightpool]

Besides, why should Mastodon support RSS 2.0 when it already support Atom?

Because we use Atom as spec'd by Ostatus, which, as evidenced in #7443, most feed readers are not equipped to handle properly.

[Sylvhem]

But, if you need to reimplement something from scratch, why not implement Atom instead of RSS?

[nightpool]

I mean, the honest reason is that's it's less complicated for us to add a new file format then to add a new route, and it's makes much stuff much less complicated from an end-users perspective. (it supports atom... twice? what?). If people want to use feed readers, they should use RSS, if they want to use Ostatus, they should use Atom.

I don't really see a compelling reason for us to "help a deprecated file format to die" if it's well-supported and fits our usecases.

[Sylvhem]

it's makes much stuff much less complicated from an end-users perspective. (it supports atom... twice? what?)

There will be the same problem with using RSS and Atom at the same time. Feed readers won't know which one to choose.

[Xanthec]

Contrary to popular belief, RSS 1.0 is normalized, being based on RDF (https://www.w3.org/RDF/) on which by the way ActivityStream is based too (which open up interesting features, by including ActivityStream data in the RSS feed).