Refactor en route to #5027 -- remove usestring parameter from lookupvar

The usestring parameter to lookupvar was objectionable for several reasons;
first, it performed a function orthogonal to the main purpose of the method,
second its default was the least common value, and third it was causing other
code to work for reasons that were not obvious (extlookup).

This refactor breaks the value-transforming function out into a seperate
method which allows the user to specify the value to be used in lieu of :undef
and removes the parameter.  The function, Scope#undef_as(default,exp) is
written so that it can be used in user code (templates, functions, etc.) if
needed.

This refactor will introduce a user-visible behaviour change in the case where
users were counting on lookupvar to return "" for undefined variables.  The
best solution is to have them use undef_as, replacing:

    lookupvar('myvar')

with

    undef_as('',lookupvar('myvar'))

(with the option to specify another default value if desired).  If this is too
objectionable, we could rename the existing lookupvar as raw_lookupvar and
define

    def lookupvar(v)
      undef_as('',raw_lookupvar(v))
    end

to restore the present behaviour.

1 files changed, 4 insertions, 4 deletions

diff --git a/spec/unit/parser/templatewrapper_spec.rb b/spec/unit/parser/templatewrapper_spec.rb
index afb0032fd..4a713b8a8 100755
--- a/spec/unit/parser/templatewrapper_spec.rb
+++ b/spec/unit/parser/templatewrapper_spec.rb
@@ -70,25 +70,25 @@ describe Puppet::Parser::TemplateWrapper do
   end
 
   it "should return the contents of a variable if called via method_missing" do
-    @scope.expects(:lookupvar).with("chicken", false).returns("is good")
+    @scope.expects(:lookupvar).with("chicken").returns("is good")
     tw = Puppet::Parser::TemplateWrapper.new(@scope)
     tw.chicken.should eql("is good")
   end
 
   it "should throw an exception if a variable is called via method_missing and it does not exist" do
-    @scope.expects(:lookupvar).with("chicken", false).returns(:undefined)
+    @scope.expects(:lookupvar).with("chicken").returns(:undefined)
     tw = Puppet::Parser::TemplateWrapper.new(@scope)
     lambda { tw.chicken }.should raise_error(Puppet::ParseError)
   end
 
   it "should allow you to check whether a variable is defined with has_variable?" do
-    @scope.expects(:lookupvar).with("chicken", false).returns("is good")
+    @scope.expects(:lookupvar).with("chicken").returns("is good")
     tw = Puppet::Parser::TemplateWrapper.new(@scope)
     tw.has_variable?("chicken").should eql(true)
   end
 
   it "should allow you to check whether a variable is not defined with has_variable?" do
-    @scope.expects(:lookupvar).with("chicken", false).returns(:undefined)
+    @scope.expects(:lookupvar).with("chicken").returns(:undefined)
     tw = Puppet::Parser::TemplateWrapper.new(@scope)
     tw.has_variable?("chicken").should eql(false)
   end