(#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>

6 files changed, 243 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
diff --git a/spec/shared_behaviours/things_that_declare_options.rb b/spec/shared_behaviours/things_that_declare_options.rb
index 19bba66c1..ecdbfcaea 100755
--- a/spec/shared_behaviours/things_that_declare_options.rb
+++ b/spec/shared_behaviours/things_that_declare_options.rb
@@ -146,4 +146,117 @@ shared_examples_for "things that declare options" do
       end
     end
   end
+
+  describe "#default_to" do
+    it "should not have a default value by default" do
+      option = add_options_to do option "--foo" end.get_option(:foo)
+      option.should_not be_has_default
+    end
+
+    it "should accept a block for the default value" do
+      option = add_options_to do
+        option "--foo" do
+          default_to do
+            12
+          end
+        end
+      end.get_option(:foo)
+
+      option.should be_has_default
+    end
+
+    it "should invoke the block when asked for the default value" do
+      invoked = false
+      option = add_options_to do
+        option "--foo" do
+          default_to do
+            invoked = true
+          end
+        end
+      end.get_option(:foo)
+
+      option.should be_has_default
+      option.default.should be_true
+      invoked.should be_true
+    end
+
+    it "should return the value of the block when asked for the default" do
+      option = add_options_to do
+        option "--foo" do
+          default_to do
+            12
+          end
+        end
+      end.get_option(:foo)
+
+      option.should be_has_default
+      option.default.should == 12
+    end
+
+    it "should invoke the block every time the default is requested" do
+      option = add_options_to do
+        option "--foo" do
+          default_to do
+            {}
+          end
+        end
+      end.get_option(:foo)
+
+      first  = option.default.object_id
+      second = option.default.object_id
+      third  = option.default.object_id
+
+      first.should_not == second
+      first.should_not == third
+      second.should_not == third
+    end
+
+    it "should fail if the option has a default and is required" do
+      expect {
+        add_options_to do
+          option "--foo" do
+            required
+            default_to do 12 end
+          end
+        end
+      }.to raise_error ArgumentError, /can't be optional and have a default value/
+
+      expect {
+        add_options_to do
+          option "--foo" do
+            default_to do 12 end
+            required
+          end
+        end
+      }.to raise_error ArgumentError, /can't be optional and have a default value/
+    end
+
+    it "should fail if default_to has no block" do
+      expect { add_options_to do option "--foo" do default_to end end }.
+        to raise_error ArgumentError, /default_to requires a block/
+    end
+
+    it "should fail if default_to is invoked twice" do
+      expect {
+        add_options_to do
+          option "--foo" do
+            default_to do 12 end
+            default_to do "fun" end
+          end
+        end
+      }.to raise_error ArgumentError, /already has a default value/
+    end
+
+    [ "one", "one, two", "one, *two" ].each do |input|
+      it "should fail if the block has the wrong arity (#{input})" do
+        expect {
+          add_options_to do
+            option "--foo" do
+              eval "default_to do |#{input}| 12 end"
+            end
+          end
+        }.to raise_error ArgumentError, /should not take any arguments/
+      end
+    end
+  end
 end
diff --git a/spec/unit/interface/action_spec.rb b/spec/unit/interface/action_spec.rb
index 23216e7b4..dbbf84778 100755
--- a/spec/unit/interface/action_spec.rb
+++ b/spec/unit/interface/action_spec.rb
@@ -552,4 +552,49 @@ describe Puppet::Interface::Action do
         to raise_error ArgumentError, /Multiple aliases for the same option/
     end
   end
+
+  context "default option values" do
+    subject do
+      Puppet::Interface.new(:default_option_values, '1.0.0') do
+        action :foo do
+          option "--foo" do end
+          option "--bar" do end
+          when_invoked do |options| options end
+        end
+      end
+    end
+
+    let :action do subject.get_action :foo end
+    let :option do action.get_option :foo end
+
+    it "should not add options without defaults" do
+      subject.foo.should == {}
+    end
+
+    it "should not add options without defaults, if options are given" do
+      subject.foo(:bar => 1).should == { :bar => 1 }
+    end
+
+    it "should add the option default value when set" do
+      option.default = proc { 12 }
+      subject.foo.should == { :foo => 12 }
+    end
+
+    it "should add the option default value when set, if other options are given" do
+      option.default = proc { 12 }
+      subject.foo(:bar => 1).should == { :foo => 12, :bar => 1 }
+    end
+
+    it "should invoke the same default proc every time called" do
+      option.default = proc { @foo ||= {} }
+      subject.foo[:foo].object_id.should == subject.foo[:foo].object_id
+    end
+
+    [nil, 0, 1, true, false, {}, []].each do |input|
+      it "should not override a passed option (#{input.inspect})" do
+        option.default = proc { :fail }
+        subject.foo(:foo => input).should == { :foo => input }
+      end
+    end
+  end
 end
diff --git a/spec/unit/interface/option_spec.rb b/spec/unit/interface/option_spec.rb
index e77b46e79..e73561fba 100755
--- a/spec/unit/interface/option_spec.rb
+++ b/spec/unit/interface/option_spec.rb
@@ -97,4 +97,48 @@ describe Puppet::Interface::Option do
       end
     end
   end
+
+  context "defaults" do
+    subject { Puppet::Interface::Option.new(face, "--foo") }
+
+    it "should work sanely if member variables are used for state" do
+      subject.default = proc { @foo ||= 0; @foo += 1 }
+      subject.default.should == 1
+      subject.default.should == 2
+      subject.default.should == 3
+    end
+
+    context "with no default" do
+      it { should_not be_has_default }
+      its :default do should be_nil end
+
+      it "should set a proc as default" do
+        expect { subject.default = proc { 12 } }.should_not raise_error
+      end
+
+      [1, {}, [], Object.new, "foo"].each do |input|
+        it "should reject anything but a proc (#{input.class})" do
+          expect { subject.default = input }.to raise_error ArgumentError, /not a proc/
+        end
+      end
+    end
+
+    context "with a default" do
+      before :each do subject.default = proc { [:foo] } end
+
+      it { should be_has_default }
+      its :default do should == [:foo] end
+
+      it "should invoke the block every time" do
+        subject.default.object_id.should_not == subject.default.object_id
+        subject.default.should == subject.default
+      end
+
+      it "should allow replacing the default proc" do
+        subject.default.should == [:foo]
+        subject.default = proc { :bar }
+        subject.default.should == :bar
+      end
+    end
+  end
 end