Raise error if Runfile exists but no tasks have been defined.

Author: schmich

runx.rb

@@ -56,6 +56,9 @@ def initialize(path, files)
   attr_reader :path, :files
 end
 
+class NoTasksDefinedError < StandardError
+end
+
 class TaskManager
   def initialize
     @tasks = {}
@@ -66,6 +69,7 @@ def load(file)
     context = TaskContext.new(dir, self)
     context.instance_eval(File.read(file), file)
     @tasks.merge!(context.tasks)
+    raise NoTasksDefinedError if @tasks.empty?
   end
 
   def show_help
@@ -234,6 +238,9 @@ def find_runfile
 rescue MultipleRunfileError => e
   $stderr.puts "[runx] Error: Multiple Runfiles found in #{e.path}: #{e.files.join(', ')}."
   exit 1
+rescue NoTasksDefinedError => e
+  $stderr.puts '[runx] Error: No tasks defined. See https://github.com/schmich/runx#usage.'
+  exit 1
 rescue TaskNotFoundError => e
   $stderr.puts "[runx] Error: Task '#{e.name}' not found."
   exit 1