Be more user-friendly when unable to find a command

* do not blow up with a stack trace if xprop is not found
* output how to debug and file a bug report when a command is not found

Fixes Issue #42

lib/launchy.rb

@@ -97,7 +97,7 @@ def dry_run?
     end
 
     def bug_report_message
-      "Please file a bug at https://github.com/copiousfreetime/launchy/issues/new"
+      "Please rerun with environment variable LAUNCHY_DEBUG=true or the '-d' commandline option and file a bug at https://github.com/copiousfreetime/launchy/issues/new"
     end
 
     def log(msg)

lib/launchy/applications/browser.rb

@@ -55,9 +55,11 @@ def browser_cmdline
       possibilities.each do |p|
         Launchy.log "#{self.class.name} : possibility : #{p}"
       end
-      browser = possibilities.shift
-      Launchy.log "#{self.class.name} : Using browser value '#{browser}'"
-      return browser
+      if browser = possibilities.shift then
+        Launchy.log "#{self.class.name} : Using browser value '#{browser}'"
+        return browser
+      end
+      raise Launchy::CommandNotFoundError, "Unable to find a browser command. If this is unexpected, #{Launchy.bug_report_message}"
     end
 
     def cmd_and_args( uri, options = {} )

lib/launchy/cli.rb

@@ -7,7 +7,7 @@ class Cli
     def initialize
       @options = {}
     end
-  
+
     def parser
       @parser ||= OptionParser.new do |op|
         op.banner = "Usage: launchy [options] thing-to-launch"

lib/launchy/detect/nix_desktop_environment.rb

@@ -14,7 +14,7 @@ class NotFoundError < Launchy::Error; end
     # NixDekstopEnvironment::Unknown
     def self.detect
       found = find_child( :is_current_desktop_environment? )
-      Launchy.log("Current Desktop environment not flound. #{Launchy.bug_report_message}") unless found
+      Launchy.log("Current Desktop environment not found. #{Launchy.bug_report_message}") unless found
       return found
     end
 
@@ -48,7 +48,11 @@ def self.browser
 
     class Xfce < NixDesktopEnvironment
       def self.is_current_desktop_environment?
-        %x[ xprop -root _DT_SAVE_MODE | grep ' = \"xfce\"$' ].strip.size > 0
+        if Launchy::Application.find_executable( 'xprop' ) then
+          %x[ xprop -root _DT_SAVE_MODE | grep ' = \"xfce\"$' ].strip.size > 0
+        else
+          false
+        end
       end
 
       def self.browser

lib/launchy/detect/runner.rb

@@ -28,7 +28,7 @@ def self.detect
         require 'spoon'
         return Jruby.new
       end
-      return Forkable.new 
+      return Forkable.new
     end
 
     #
@@ -55,6 +55,7 @@ def dry_run( cmd, *args )
     end
 
     def run( cmd, *args )
+      raise Launchy::CommandNotFoundError, "No command found to run with args '#{args.join(' ')}'. If this is unexpected, #{Launchy.bug_report_message}" unless cmd
       if Launchy.dry_run? then
         $stdout.puts dry_run( cmd, *args )
       else

lib/launchy/error.rb

@@ -1,4 +1,5 @@
 module Launchy
   class Error < ::StandardError; end
   class ApplicationNotFoundError < Error; end
+  class CommandNotFoundError < Error; end
 end

spec/detect/nix_desktop_environment_spec.rb

@@ -22,6 +22,10 @@
     end
    end
 
+  it "returns false for XFCE if xprop is not found" do
+    Launchy.host_os = "linux"
+    Launchy::Detect::NixDesktopEnvironment::Xfce.is_current_desktop_environment?.must_equal( false )
+  end
 
   it "returns nil if it cannot determine the *nix desktop environment" do
     Launchy.host_os = "linux"

spec/detect/runner_spec.rb

@@ -20,6 +20,11 @@
     lambda{ Launchy::Detect::Runner.detect }.must_raise Launchy::Detect::RubyEngine::NotFoundError
   end
 
+  it "raises and error when there is no command found" do
+    runner = Launchy::Detect::Runner.detect
+    lambda{ runner.run( nil, *%w[ arg1 arg2 arg 3] ) }.must_raise Launchy::CommandNotFoundError
+  end
+
   # On anything that has fork, use Forkable
   %w[ linux darwin cygwin ].each do |host_os|
     %w[ ruby rbx macruby ].each do |engine_name|

spec/spec_helper.rb

@@ -1,5 +1,5 @@
 gem 'minitest'
-require 'minitest/autorun'
-require 'minitest/pride'
 require 'launchy'
 require 'stringio'
+require 'minitest/autorun'
+require 'minitest/pride'