a wrapper of sourceCpp which keeps the shared library file.

importCpp.R

importCpp <- function(infile, output_dir="lib", rebuild=FALSE){
    output_dir = ifelse(is.null(output_dir), ".", output_dir)
    dir.create(output_dir, recursive=T, showWarnings=FALSE)
    outfile = file.path(output_dir, paste0(infile, ".R"))

    if (!file.exists(outfile) || file.info(infile)$mtime > file.info(outfile)$mtime || rebuild){
        Rcpp::sourceCpp(infile, rebuild=rebuild)
        context = .Call("sourceCppContext", PACKAGE = "Rcpp",
            normalizePath(infile, winslash = "/"), code=NULL, 0L, .Platform)
        scriptfile = file.path(context$buildDirectory, context$rSourceFilename)
        content = readLines(scriptfile)
        ext = .Platform$dynlib.ext
        m = regexpr(paste0("(?<=dyn.load\\(').*", ext), content[1], perl=TRUE)
        shlibfile = file.path(output_dir, paste0(infile, ext))
        shlibfile0 = regmatches(content[1], m)
        content[1] = sub(shlibfile0, shlibfile, content[1])

        f = file(outfile, "w+")
        writeLines(content, f)
        close(f)
        file.copy(shlibfile0, shlibfile, overwrite=TRUE)
    }else{
        source(outfile)
    }
    return(outfile)
}

@sdwfrost: The relevant names to generate the cache path seem to be here: https://github.com/RcppCore/Rcpp/blob/master/R/Attributes.R#L35-L37

— At least using this seems to work.