(#6787) Add `default_to` for options.

This implement support for options with default values, allowing faces to set
those values when not invoked.  This can eliminate substantial duplicate code
from actions, especially when there are face-level options in use.

Reviewed-By: Pieter van de Bruggen <pieter@puppetlabs.com>

3 files changed, 41 insertions, 0 deletions

diff --git a/lib/puppet/interface/action.rb b/lib/puppet/interface/action.rb
index fe77a9658..fc1121eb6 100644
--- a/lib/puppet/interface/action.rb
+++ b/lib/puppet/interface/action.rb
@@ -199,6 +199,7 @@ def #{@name}(#{decl.join(", ")})
   options = args.last
 
   action = get_action(#{name.inspect})
+  action.add_default_args(args)
   action.validate_args(args)
   __invoke_decorations(:before, action, args, options)
   rval = self.__send__(#{internal_name.inspect}, *args)
@@ -252,6 +253,14 @@ WRAPPER
     option
   end
 
+  def add_default_args(args)
+    options.map {|x| get_option(x) }.each do |option|
+      if option.has_default? and not option.aliases.any? {|x| args.last.has_key? x}
+        args.last[option.name] = option.default
+      end
+    end
+  end
+
   def validate_args(args)
     # Check for multiple aliases for the same option...
     args.last.keys.each do |name|
diff --git a/lib/puppet/interface/option.rb b/lib/puppet/interface/option.rb
index 3cd930acf..01f6f2307 100644
--- a/lib/puppet/interface/option.rb
+++ b/lib/puppet/interface/option.rb
@@ -6,6 +6,7 @@ class Puppet::Interface::Option
   def initialize(parent, *declaration, &block)
     @parent   = parent
     @optparse = []
+    @default  = nil
 
     # Collect and sort the arguments in the declaration.
     dups = {}
@@ -81,8 +82,26 @@ class Puppet::Interface::Option
     !!@required
   end
 
+  def has_default?
+    !!@default
+  end
+
+  def default=(proc)
+    required and raise ArgumentError, "#{self} can't be optional and have a default value"
+    proc.is_a? Proc or raise ArgumentError, "default value for #{self} is a #{proc.class.name.inspect}, not a proc"
+    @default = proc
+  end
+
+  def default
+    @default and @default.call
+  end
+
   attr_reader   :parent, :name, :aliases, :optparse
   attr_accessor :required
+  def required=(value)
+    has_default? and raise ArgumentError, "#{self} can't be optional and have a default value"
+    @required = value
+  end
 
   attr_accessor :before_action
   def before_action=(proc)
diff --git a/lib/puppet/interface/option_builder.rb b/lib/puppet/interface/option_builder.rb
index 5676ec977..c87adc2c0 100644
--- a/lib/puppet/interface/option_builder.rb
+++ b/lib/puppet/interface/option_builder.rb
@@ -51,4 +51,17 @@ class Puppet::Interface::OptionBuilder
   def required(value = true)
     @option.required = value
   end
+
+  def default_to(&block)
+    block or raise ArgumentError, "#{@option} default_to requires a block"
+    if @option.has_default?
+      raise ArgumentError, "#{@option} already has a default value"
+    end
+    # Ruby 1.8 treats a block without arguments as accepting any number; 1.9
+    # gets this right, so we work around it for now... --daniel 2011-07-20
+    unless block.arity == 0 or (RUBY_VERSION =~ /^1\.8/ and block.arity == -1)
+      raise ArgumentError, "#{@option} default_to block should not take any arguments"
+    end
+    @option.default = block
+  end
 end