Invalid Display Names in Feature Tags

[arinoch]

Quick summary

Tags with invalid characters fail to be imported into instances such as Mastodon, Glitch-soc, etc.

Steps to reproduce

1. Create a tag using this plugin that includes characters that would not be valid in a standard hashtag.
2. Publish content to the fediverse under that tag.
3. From another instance that you might be federated with, try to search for your content using that tag.
4. You will not be able to see your content on the remote instance.
5. Admins of that instance, when looking at related jobs for your site, will see: "Validation failed: Name is invalid, Display name is invalid"

Affected URL: /actors/2/collections/tags

Proposed Solution: The plugin should sanitize tags at this URL to conform with standard hashtag syntax, and not use international characters when pushing content to the fediverse.

Site owner impact

Fewer than 20% of the total website/platform users

Severity

Minor

What other impact(s) does this issue have?

No response

If a workaround is available, please outline it here.

Users can rename an invalid tag to conform to standard hashtag syntax (no international characters), but the solution should come from the plugin authors (see above).

[pfefferle]

Is it only an issue that the specific tag is not imported, or is the whole post blocked?

Can you specify "Invalid Characters" a bit more? Mastodon supports quite a lot of special chars, so it is hard to decide when something is not supported and when is.

[arinoch]

Hi @pfefferle! It doesn't give me a specific post that failed, but only the link to the tag collection that's being rejected. A quick investigation of the JSON doesn't reveal anything obvious, but every occurrence of this issue points to the exact same JSON file so I suspect something isn't being sanitized properly there.

Example JSON: https://public-api.wordpress.com/wpcom/activitypub-1.0/sites/1827312/actors/0/collections/tags

[arinoch]

Upon further review, I suspect I might have identified the issue.

The tags in my example JSON file above include the hashtag (#) symbol in the display name. Since you can't search for a hashtag called "##hello", this might be why the JSON is being rejected.

CC: @pfefferle

[pfefferle]

We can for sure fix that!

[pfefferle]

Just had a look, that is how it should be! See https://mastodon.social/users/pfefferle/collections/tags

[arinoch]

You are of course right and I was looking at it before coffee. :) But that does confirm that I don't see anything super obvious that could be breaking it with this plugin. I can absolutely confirm that it is only this plugin that is generating that error, however, on multiple sites both self-hosted and managed.

[arinoch]

Okay, I found the super not obvious thing that is breaking your plugin. Mastodon will ignore entirely numeric hashtags, which all of the sites throwing this error are using. So hashtags like #2025 will absolutely not work. Or, like in the JSON example, #3. If you tried to add 2025 to the list of tags that you showed me, Mastodon wouldn't let you. So the plugin needs to either ignore numeric tags when sending these collections to the fediverse or explicitly tell the user (and hopefully also reject the tag) that numeric-only tags are not compatible.

My example JSON file only has numeric hashtags. Your corresponding JSON file does not. Mastodon's tag API docs say it will reject numeric hashtags. And there we have "invalid display name".

CC: @pfefferle

[pfefferle]

It's hard to sanitize these 😉

[arinoch]

Yup. ;) But I even tested it by posting a toot with the hashtag #1984 and the platform refused to treat it as a hashtag, so that's definitely the problem you have.

[pfefferle]

I am not sure if that is the problem "I" have :)

So even if numeric hashtags might fail on Mastodon, they are allowed on WordPress and maybe on other platforms too. I think the best option we have is to keep it failing on some of the platforms!?

What do you think?

(I will close this for now, because I think it is not really a bug, but feel free to continue the discussion here)