install_rosetta: add upgrade argument

 - closes #10

R/install_rosetta.R

@@ -8,6 +8,7 @@
 #' @param pip _logical_. Use `pip` for package installation? Default: `TRUE`. This is only relevant when Conda environments are used, as otherwise packages will be installed from the Conda repositories.
 #' @param system _logical_. Default: `FALSE`. If `TRUE`, try installing to system (user) site library with `system()` and set reticulate to use system Python.
 #' @param user _logical_. Default: `FALSE`. Pass `--user` flag. This should only be done if other installation methods fail and it is impossible to use a virtual environment.
+#' @param upgrade _logical_. Install latest versions of Python packages by passing `--upgrade` flag? Default: `TRUE`.
 #' @param arcpy_path Argument passed to `find_python()`. Path to ArcGIS Pro Python installation e.g. ``. Set as `NULL` (default) to prevent use of ArcGIS Pro instance.
 #'
 #' @details From `reticulate::py_install()`: On Linux and OS X the "virtualenv" method will be used by default ("conda" will be used if virtualenv isn't available). On Windows, the "conda" method is always used.
@@ -21,6 +22,7 @@ install_rosetta <- function(envname = NULL,
                             conda = "auto",
                             pip = TRUE,
                             user = FALSE,
+                            upgrade = TRUE,
                             system = FALSE,
                             arcpy_path = getOption("rosettaPTF.arcpy_path")) {
 
@@ -39,10 +41,12 @@ install_rosetta <- function(envname = NULL,
   if (isFALSE(system)) {
     # get rosetta-soil (and numpy if needed)
     try(reticulate::py_install("rosetta-soil", envname = envname, method = method,
-                               conda = conda, pip = pip, pip_options = ifelse(user, "--user", "")), silent = TRUE)
+                               conda = conda, pip = pip, pip_options = c(ifelse(user, "--user", character()),
+                                                                         ifelse(upgrade, "--upgrade", character()))), silent = TRUE)
   } else {
     reticulate::use_python(p, required = TRUE)
-    try(system(paste(shQuote(p), "-m pip install --upgrade --user rosetta-soil")), silent = TRUE)
+    try(system(paste(shQuote(p), "-m pip install", ifelse(upgrade, "--upgrade", ""),
+                                                   ifelse(user, "--user", ""), "rosetta-soil")), silent = TRUE)
   }
 
   # load modules globally in package (prevents having to reload rosettaPTF library in session)