Project specific snapshot dependencies for R

.init.R

local({
    # https://packagemanager.posit.co/client/#/repos/cran/setup
    url = "https://packagemanager.posit.co/cran/2023-09-01"
    r_version = gsub("\\.\\d+$", "", as.character(getRversion()))
    cran_version = rev(unlist(strsplit(url, "/+")))[1]
    dir = sprintf("~/.R/library/%s-%s", r_version, cran_version)
    message(sprintf("Using %s", url))
    message(sprintf("Using %s", dir))
    options(repos=url)
    if (!dir.exists(dir))
        dir.create(dir, recursive=TRUE)
    .libPaths(dir)
})

.Rprofile

local({
    # Source any possible project-specific .init.R first
    # as it might set .libPaths for custom dependencies.
    # https://gist.github.com/otsaloma/f3b8f61a39bf81df0bcc0e5fd80e9ad1
    components = unlist(strsplit(getwd(), "/"))
    for (i in length(components):1) {
        args = as.list(c(components[1:i], ".init.R"))
        path = do.call(file.path, args)
        if (file.exists(path)) {
            source(path)
            break
        }
    }
})

# Make sure your later .Rprofile doesn't overwrite the above,
# e.g. if you want to set default repos, use the following form.
# options(repos=getOption("repos", "https://cran.rstudio.com/"))

Put the .init.R file in your project root and a piece of code that loads it at the very top of your ~/.Rprofile. Whenever you start R anywhere under the project directory, it should load the snapshot library. Installing packages and everything else should work as normal. If you need custom dependencies, not available in CRAN and the corresponding MRAN snapshot, just add them to the end of .init.R.

Updated to use RStudio's snapshots as Microsoft's MRAN has been unreliable for a while now.