allow installing package dependencies from single repo (fixes #1762)

src/cpp/session/modules/ModuleTools.R

@@ -1,7 +1,7 @@
 #
 # ModuleTools.R
 #
-# Copyright (C) 2009-15 by RStudio, Inc.
+# Copyright (C) 2009-17 by RStudio, Inc.
 #
 # Unless you have received this program directly from RStudio pursuant
 # to the terms of a commercial license agreement with RStudio, then
@@ -121,19 +121,17 @@
   # the repos option is canonically a named character vector, but could also
   # be a named list
   if (is.character(repos) || is.list(repos)) {
-    if (is.null(names(repos))) {
-      # no indication of which repo is which, presume the first entry to be
-      # CRAN if it's of character type
-      if (length(repos) > 0 && is.character(repos[[1]]))
-        repo <- repos[[1]]
-    } else {
-      # use repo named CRAN
-      repo <- as.character(repos["CRAN"])
+    # check for a repo named "CRAN"
+    repo <- as.character(repos["CRAN"])
+
+    # if no repo named "CRAN", blindly guess that the first repo is a CRAN mirror 
+    if (length(repo) < 1 || is.na(repo)) {
+      repo <- as.character(repos[[1]])
     }
   }
 
   # if no default repo and no repo marked CRAN, give up
-  if (is.na(repo)) {
+  if (length(repo) < 1 || is.na(repo)) {
     return(list(version = "", satisfied = FALSE))
   }