fix #181: don't run tlmgr path add if /usr/local/bin/tlmgr doesn't …

…exist, which is possible when TinyTeX is installed with the --no-path option, and no symlinks will be created to /usr/local/bin

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: tinytex
 Type: Package
 Title: Helper Functions to Install and Maintain 'TeX Live', and Compile 'LaTeX' Documents
-Version: 0.20.1
+Version: 0.20.2
 Authors@R: c(
   person("Yihui", "Xie", role = c("aut", "cre", "cph"), email = "[email protected]", comment = c(ORCID = "0000-0003-0645-5666")),
   person(family = "RStudio, PBC", role = "cph"),

R/tlmgr.R

@@ -116,6 +116,9 @@ tlmgr_install = function(pkgs = character(), usermode = FALSE, path = !usermode
     }
     if (Sys.which('gs') == '') warning('GhostScript is required for the epstopdf package.')
   }
+  # only run `tlmgr path add` if the symlink for tlmgr exists under
+  # /usr/local/bin; it may not exist when TinyTeX is installed with --no-path
+  if (missing(path)) path = path && file.exists('/usr/local/bin/tlmgr')
   if (path) tlmgr_path('add')
   invisible(res)
 }