more informative error on install

Rmagic/R/magic.R

@@ -1,5 +1,5 @@
 #' Perform MAGIC on a data matrix
-#' 
+#'
 #' Markov Affinity-based Graph Imputation of Cells (MAGIC) is an
 #' algorithm for denoising and transcript recover of single cells
 #' applied to single-cell RNA sequencing data, as described in
@@ -83,7 +83,7 @@ magic <- function(data,
                   seed=NULL) {
   # check installation
   if (!reticulate::py_module_available(module = "magic")) {
-    install.magic()
+    load_pymagic()
   }
   tryCatch(pymagic, error = function(e) load_pymagic())
   k <- as.integer(k)

Rmagic/R/utils.R

@@ -9,20 +9,20 @@ null_equal <- function(x, y) {
   }
 }
 
-load_pymagic <- function() {
-  pymagic <<- reticulate::import("magic", delay_load = TRUE)
+load_pymagic <- function(delay_load = FALSE) {
+  result <- try(pymagic <<- reticulate::import("magic", delay_load = delay_load))
+  if (methods::is(result, "try-error")) {
+    install.magic()
+  }
 }
 
-#' Install PHATE Python Package
+#' Install MAGIC Python Package
 #'
-#' Install PHATE Python package into a virtualenv or conda env.
+#' Install MAGIC Python package into a virtualenv or conda env.
 #'
 #' 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.
-#' As of reticulate v1.7, this functionality is only available in the
-#' development version of reticulate, which can be installed using
-#' `devtools::install_github('rstudio/reticulate')`
 #'
 #' @param envname Name of environment to install packages into
 #' @param method Installation method. By default, "auto" automatically finds
@@ -39,13 +39,13 @@ load_pymagic <- function() {
 install.magic <- function(envname = "r-reticulate", method = "auto",
                           conda = "auto", pip=TRUE, ...) {
   stop(paste0(
-      "Cannot install MAGIC, please install from a console with ",
+      "Cannot locate MAGIC Python package, please install from a console with ",
       "pip install --user git+git://github.com/KrishnaswamyLab/MAGIC.git#subdirectory=python"
     ))
 }
 
 pymagic <- NULL
 
 .onLoad <- function(libname, pkgname) {
-  load_pymagic()
+  load_pymagic(delay_load = TRUE)
 }