Add language support for NAMESPACE & .Rbuildignore

[nx10]

Edit: not sure if "language support" is the right terminology. Maybe "syntax highlighting grammars and configurations" would be correct.

What problem did you solve?

This PR adds language support for NAMESPACE and .Rbuildignore R package files according to the specification:

• Namespaces: https://cran.r-project.org/doc/manuals/R-exts.html#Package-namespaces
  • Written from scratch
  • Visually differentiates imports and exports and highlights im-/exported symbols
• R ignore: https://cran.r-project.org/doc/manuals/R-exts.html#Building-package-tarballs
  • JavaScript Regex grammar is dynamically imported
  • Much easier to visually parse lines and not wrongly detected as XML anymore

Screenshots

Note

(I am currently participating in the hacktoberfest. If you like this PR consider to tag it with hacktoberfest-accepted .)

[renkun-ken]

Thanks for working on this?

Looks like NAMESPACE file is more like R syntax, just like the following:

• https://github.com/r-lib/lintr/blob/main/NAMESPACE
• https://github.com/Rdatatable/data.table/blob/master/NAMESPACE

where both do some R version checking.

Is there a reason we don't just use R syntax and extend a bit if helpful?

[nx10]

Thanks for working on this?

Looks like NAMESPACE file is more like R syntax, just like the following:

• https://github.com/r-lib/lintr/blob/main/NAMESPACE
• https://github.com/Rdatatable/data.table/blob/master/NAMESPACE

where both do some R version checking.

Is there a reason we don't just use R syntax and extend a bit if helpful?

Interesting, the documentation does mention version checks, I wonder if general R code is allowed in these files.
I will see if I can link with the R grammar for everything that is not an import/export directive.

As for the use-case: I find myself looking at NAMESPACE files solely to figure out what symbols a package imports and exports, which I tried to simplify with this. I realize that this is subjective so it's perfectly fine if you don't want to merge this feature.

The problem with extending the R grammar is that the NAMESPACE directives are legal symbols in R:

> S3method
Error: object 'S3method' not found
> S3method <- "asd"
> S3method 
[1] "asd"
> import
Error: object 'import' not found
> import <- 12
> import
[1] 12

so it would be wrong to highlight them differently in R code files.

[renkun-ken]

It seems that most functions in baseenv are allowed at compile time. We might need to add highlighting for if else, string literal and simple function calls.

I tried something like the following and it works, but anything like utils::capture.output won't work with an error raised.

export(fun1)
export(fun2)
export(fun3)

if (findInterval(1, c(0, 1)) >= 1) {
  export(fun4)
}

parseNamespaceFile() is called on package installation to parse NAMESPACE file.

[renkun-ken]

Let's merge this first and revisit if we need further improvements.

[nx10]

Thanks! It's not easy to to fall back to the R grammer for everything but specific functions as the grammar is "hungry" and once a scope starts (i.e. with {, () it will completely take over. I am pretty sure there is a way to do it but I could not find it in the short time I tried.