Don't crash when asking for help on invalid cmd.

2 files changed, 2 insertions, 1 deletions

diff --git a/src/luarocks/help.lua b/src/luarocks/help.lua
index 0a155509..e6c214ff 100644
--- a/src/luarocks/help.lua
+++ b/src/luarocks/help.lua
@@ -100,7 +100,7 @@ function help.run(...)
       end
    else
       command = command:gsub("-", "_")
-      local cmd = require(commands[command])
+      local cmd = commands[command] and require(commands[command])
       if cmd then
          local arguments = cmd.help_arguments or "<argument>"
          print_banner()
diff --git a/test/testing.sh b/test/testing.sh
index 4b159892..5018abe0 100755
--- a/test/testing.sh
+++ b/test/testing.sh
@@ -365,6 +365,7 @@ test_download_all() { $luarocks download --all validate-args && rm validate-args
 test_download_rockspecversion() { $luarocks download --rockspec validate-args ${verrev_validate_args} && rm validate-args-*; }
 
 test_help() { $luarocks help; }
+fail_help_invalid() { $luarocks help invalid; }
 
 test_install_binaryrock() { $luarocks build --pack-binary-rock cprint && $luarocks install ./cprint-${verrev_cprint}.${platform}.rock && rm ./cprint-${verrev_cprint}.${platform}.rock; }
 test_install_with_bin() { $luarocks install wsapi; }