Improve test coverage (and rewrite parser)

[JojOatXGME]

The project currently lacks automatic tests for the Java implementation. Within this ticket, I want to add tests for the most important components.

[JojOatXGME]

While working on this ticket, I noticed some issues with the parser. I initially wanted to fix the issues incrementally, but I eventually decided to rewrite the parser. I guess I might create a pull request at the end of the week.

Anyway, I noticed that the parser of the plugin had support for some expressions and keywords I couldn't find in the Nix language itself. The related keywords are

• require,
• requires,
• import, and
• imports.

@pSub or @Mic92, do you have any idea where these keywords are coming from? Did Nix had any breaking changes which might have removed these keywords?

@edwtjo, I mention you because you have created the initial version of the parser six years ago according to GitHub. The initial version already supported these keywords. Maybe you can still remember the background?

EDIT: Well, I guess import just refers to the built-in function (which is not a keyword). Strange that I didn't think about that until after writing this comment. 😅 I could not find functions for the other terms in the manual, though.

[Mic92]

Imports is used only in NixOS modules where it is not a module but an attribute in your configuration attribute set. import is a builtin function as you found out. I never saw require or requires being used for anything.

[JojOatXGME]

Just a short update for everyone interested:

My new parser implementation seems to work fine as long as the file is valid. I currently try to find a good approach to recover from syntax errors. I actually created a post on intellij-support.jetbrains.com about one of my problems. I will invest some more time and try to find a good solution. Anyway, I hope that even without reliable error recovery, my new parser implementation (with test coverage and Nix 2.3-support) would be an improvement.

My current status can be found on the tests branch of my fork. However, if you look at this branch, be aware that I rebase this branch from time to time.