fix #1125 Friendly configuration for icons

[braver]

• make it less easy to make little mistakes
• make third party gutter themes easier to use

Fixes #1125

[kaste]

Requesting @Monokai for review bc the python code itself is simple but I don't have any themes to do a functional test.

[Monokai]

@kaste Already commented here: #1125 (comment)

[kaste]

Okay, thanks. Explicit is the base implementation, anything more convenient (automatic) must go on top of that. I like the failing icon we have right now.

So, what the code does.

User sets theme: a/b/c.gutter-theme, icon to 'warning' => resolved icon 'a/b/warning.png'
User sets theme: a/nothere/c.gutter-theme icon to 'warning' => resolved icon 'FAIL'
User sets theme: a/b/c.grutterteme, resolved icon 'FAIL'

So, a more convenient experience can be e.g. theme: c -> searches for c.gutter-theme or FAIL

[braver]

So, a more convenient experience can be e.g. theme: c -> searches for c.gutter-theme

We provide that experience for our built-in themes. You set it to 'Danish Royalty' and we understand that to mean 'Packages/SublimeLinter/gutter-themes/Danish Royalty/Danish Royalty.gutter-theme'.

We could use find_resources instead (and that's basically what @Monokai proposes too) and let Sublime Text figure out where Danish Royalty.gutter-theme hangs out. However, that means that if <Some Package Earlier In The Alphabet Than SublimeLinter> has a Danish Royalty.gutter-theme it will try to use that and maybe fail because who knows what that is. Now, this is perhaps unlikely, but we get enough people asking us to debug their computer for them and debugging style things is about the least exciting thing I can think of.

We could also first try to see if 'Danish Royalty' is a theme we know, and if not then look for it using find_resources. However, as I noted in my reaction in #1125, how do you know to put 'Danish Royalty' in that setting in the first place? You probably copied that from somewhere. Why do we have to go looking for it if you (or the provider of said gutter theme) knows exactly where it is?

[kaste]

I just don't see that we need more than this. 🚢

[braver]

I just don't see that we need more than this.

Same. 🤘