Auto-generated kern feature could have wrong languagesystems

Does anyone understand why the current ufo2ft code runs a regexp over features.fea to find the language systems for the auto-generated features? The current logic seems a little surprising, and it might not work reliably.

• The current logic assumes that there’s a manually entered feature file. That’s not guaranteed — a valid UFO may just kerning.plist but no features.fea.

• Why should the languagesystems of some random GSUB or aalt feature determine the languagesystems for the kern feature?

• The current regexp doesn’t actually retrieve the feature content in a reliable way. A feature file can include other feature files. Also, it doesn’t catch script statements.

Instead of the current logic, why doesn’t the code consider the Unicode codepoints being kerned? It would be tempting to just re-write this code, but I’d like to understand the rationale behind the current logic. Maybe there’s a reason for it?

Start by locating the ufo2ft code that runs a regexp over features.fea to derive language systems for auto-generated features. Read the surrounding feature-generation logic and inspect how missing feature files, included files, and script statements are handled. Done means the rationale is documented and a reliable replacement behavior is agreed for kern language systems.