Rails has the method font_url which I'm fairly certain is what is being invoked. However, I can't find where the connection between these two things is made. I have explored the codebases of bourbon, sass, sass-rais, and rails.
Where is font-url defined, and/or the connection between it and rails's font_url made?
update
Clarification: my ultimate goal is to define my own helpers in rubyland which are siblings to font_url.
font-url is a part of rails asset pipeline just like image-url. If you look at rail guides it clearly says
When using the asset pipeline, paths to assets must be re-written and sass-rails provides -url and -path helpers (hyphenated in Sass, underscored in Ruby) for the following asset classes: image, font, video, audio, JavaScript and stylesheet.
So if you are using font-url("some_font") it will look for some_font in app/assets/font directory
Update:
As it is mentioned in docs that if you are using sass then your can use your assets with hypenated urls(image-url) but if you are using a ruby file then those helpers would be underscored (image_url) probably because Ruby doesn't like you having methods or variables with hyphens in the name syntactically, but semantically, there's nothing wrong with it
来源：https://stackoverflow.com/questions/25457893/where-does-the-sass-font-url-method-get-defined