f31878bc2c
Fix searches like this:
https://danbooru.donmai.us/artist_urls?search[url_not_regex]=https://www/.artstation/.com/[a-zA-Z0-9-.]
returning a HTTP 500 error with a blank page.
Here the problem is that Postgres raises an error because `[a-zA-Z0-9-.]`
is an invalid character class (it should be `[a-ZA-Z0-9.-]`). This error
happens on the error page itself, when rendering the <link rel="next"> /
<link rel="prev"> links in the <head>, so it causes the error page to fail.
Helpers
This directory contains helper functions used by views. Helpers are used for simple common functions, such as linking to users or formatting timestamps.
Helper functions are globals. If you see an unnamespaced function in a view, and it's not a Rails function, then it's probably a helper defined here.
All helper functions defined in this directory are globally available to all views. They're not limited to single views. For example, the functions in posts_helper.rb are available to all views, not just to app/views/posts.
The use of helper functions should be minimized. Partials or components are preferred for more complex widgets, or for things used in only one or two places. Helper functions should be limited to very simple things used in nearly all views.