Pavels work + unit tests

[radbasa]

Description

• First step in building a dev framework for languageserver parser hook. (Move box use parser function into its own discrete function #6)
• Imported Pavel's work as is.
• Copied test helper utilities from languageserver
• Add regression unit test copied from languageserver unit test test-completion.R
• Add test for pkg[...] function name completion.

Definition of Done

• The change is thoroughly documented.
• The CI passes (R CMD check, linter, unit tests, spelling).
• Any generated files have been updated (e.g. .Rd files with roxygen2::roxygenise())

[radbasa]

Couldn't get R CMD Check to see the .Rprofile in CI. Decided to just run testthat::test_dir() manually.

[Gotfrid]

Here are a few comments on what else works (code completion only)

1. box::use(pkg) also works after this change (see attached video)
2. box::use(pkg[attach_list]) kinda works - it will load all functions from a package, not limited to the ones in the attach_list.
3. prefix/mod[attach_list] also works - just the bare minimum code completion tho, which is based solely on text parsing: i can box::use() a non-existent function, so not sure if we should check it (see second video).

Screen.Recording.2024-06-06.at.07.46.19.mov

Screen.Recording.2024-06-06.at.07.51.54.mov

[radbasa]

@Gotfrid , the plans are:

1. box::use(pkg): To auto-complete on pkg$... such as dplyr$ should show dplyr$across, or dplyr$fi should show dplyr$filter.
2. box::use(pkg[attach_list]): to only auto-complete the attached functions

Same goes for path/modules.

Then there are the aliases.