Chat Command to test longer posts

[micsthepick]

Is your feature request related to a problem? Please describe.

Sometimes I want to test messages that are longer than the chat command length, but there's not a simple way to do so.

Describe the solution you'd like

#13245 - Implement a chat command to test a post by a plaintext download url.

Describe alternatives you've considered

Making a real sandbox post with the contents - let's not go there!

Additional context

[makyen]

I'd substantially prefer that the capability to test longer text be implemented by accepting multi-line chat messages. Doing so would leave a record of what was actually tested, rather than just a reference to a URL which would, eventually, become invalid.

[micsthepick]

I'd substantially prefer that the capability to test longer text be implemented by accepting multi-line chat messages. Doing so would leave a record of what was actually tested, rather than just a reference to a URL which would, eventually, become invalid.

If you have an idea of how this would look I am all ears. There may be unsupported characters that need consideration too such as the newlines themselves.

[CoconutMacaroon]

@micsthepick cc @makyen I've been working on multiline chat message support, and one of the fixes I'm currently working on may enable this functionality without more work. See #12803, which more-or-less is for SD support of multiline messages that are fairly short. I have a somewhat-tested theory on fixing that, although I don't know when exactly I'll have a chance to implement and test that fix.

If the !!/test command supporting multiline messages would be a suitable fix, I'd probably suggest waiting until I fix that bug, as there's a decent chance that would be enough to enable multiline use of !!/test.

Newlines present via multiline messages (i.e., Shift + Enter) would likely be persisted as <br> (I believe that gets transformed into \n). But I'd have to go back and double-check exactly what happens to newlines.