Short intro and scope

Hi @richfitz and @mllg

Very short introductions below.

Rich and I work at Imperial together. Rich has worked on many many R projects but most relevant here is provisionr and in particular the package_sources function for collecting info on package sources. But I believe Rich is planning on deprecating the function and/or package.

Michel is the main developer on the mlr3 project, which is our primary use-case for this package (though hope would generalise well).

Both very experienced in R6 and R programming in general but here we are looking at something that should be fairly simple and stripped back (S3 only).

This issue covers my motivation and some basic design ideas. Essentially I need a way of cleanly storing and querying package information for mlr3extralearners, which preferably includes package name and location.

At a minimum I think we need one function that can construct an S3 class that provides information about the package name and location. provisionr includes packages from github, cran, drat, local-- I think in addition we should include Bioconductor and release URLs.

We could also consider a separated class that holds all the packages that could be useful for install methods and printing.

Some links to another implementation by Michel to something similar to this: https://github.com/rdatsci/rtcl/blob/master/R/stringToPackage.r https://github.com/rdatsci/rtcl/blob/master/R/Packages.r https://github.com/rdatsci/rtcl/blob/master/R/installPackage.r

Start by reading provisionr's R/package_sources.R and the linked mlr3 issue, then compare the related rtcl files: R/stringToPackage.r, R/Packages.r, and R/installPackage.r. Done means agreeing on an S3 representation that stores package name and location and covers the proposed package sources, including Bioconductor and release URLs.