Design nicer error/placeholder pages

[tobyzerner]

Remaining from #118:

• Error page designs (404.html, 500.html)
• Design and handle error messages for empty sections
  • Discussion list (e.g. search, see When searching for something with few characters doesn't throw error. issue-archive#368 773)
  • User profile: Activity
  • User profile: Mentions (see Blank screen if no mentions are available on the mentions tab (profile) #1489)
  • more?
• Design and handle error page for discussion not found, user not found, route not found, etc.

[franzliedke]

404 pages should contain a login form.

[tobyzerner]

Kind of also the same as #252 but meh

[benjaminfrombe]

I guess a temporary workaround can be to have a refresh to the login page in the 403 and 404.html pages ... That's how I fixed it for the time being anyway ...

[franzliedke]

@edd-- Yep, that's a good idea!

[OrdinaryJellyfish]

i have a simple idea for error pages:

Should I open a PR to add these @tobscure @franzliedke ?

[luceos]

I'd prefer to use the compiled (if possible) stylesheet and use that styling @TristianK3604 .

[franzliedke]

I'd prefer to use the compiled (if possible) stylesheet

@luceos Why? I think it's good when error pages are self-contained, and so far that's what we have been doing...

[luceos]

I wasn't aware about that decision. I nevertheless don't think it's a big deal to include the stylesheet, if it doesn't exist it won't break the page anyway.

[tobyzerner]

The design aspect of this issue is already solved in 9392e1b and b7c1cc5

(See https://discuss.flarum.org/asdf for an example)

[askvortsov1]

The user mentions, posts, and discussions pages now all have empty messages.
As to custom messages for discussion not found, route not found, user not found, this should all be handled by flarum/issue-archive#206.

That leaves "too few characters = no discussions" as the only issue; as such, I will reopen https://github.com/flarum/core/issues/773 (if it's not really needed, stable bot will remove it) and close this.