Custom Functions are poorly documented

[layton-glympse]

Documentation around the custom functions experimental feature is poor. It says they are available, and even shows how to make a call to renderSync(), but it doesn't explain how those functions are surfaced from within SASS.
Unless I'm misunderstanding how this works, the documentation does say:

...a collection of custom functions that may be invoked by the sass files being compiled...

The syntax around setting up these functions is confusing, as it seems to be defined with a stringified function call followed by a "similar" function signature. But there is no real explanation around what these things mean, or any explanation of how to call said custom function from within sass.

Reading the source code to figure it out makes the Readme moot. I would appreciate a better explanation and an update of the readme, if possible.

Thanks!

[emanuel-macoun]

After almost one year, custom function are still marked as experimental feature. Is this still issue? Or are there any plans to bring this feature into stable version?

[saper]

node-sass does not have "stable versions" right now. The issue with custom importers and custom functions that there are still issues that are hard to resolve (like #857) and might need a major change to how things work (if possible at all). There is also an undecided issue how to deal with sass types further (#1088, #1320) and other issues (#911).

Experimental means that the way those things are defined and used can be changed dramatically. For example, sass_types might be gone or completely replaced.

[emanuel-macoun]

Hi Saper, thanks for explanation. For now, the custom function feature works well for me, I don't mind using sass types for now, but I'll obviously welcome native types support.