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.

12 files changed, 63 insertions, 94 deletions

diff --git a/lib/puppet/parser/ast/leaf.rb b/lib/puppet/parser/ast/leaf.rb
index 77617e992..b61634d6c 100644
--- a/lib/puppet/parser/ast/leaf.rb
+++ b/lib/puppet/parser/ast/leaf.rb
@@ -124,7 +124,7 @@ class Puppet::Parser::AST
     # not include syntactical constructs, like '$' and '{}').
     def evaluate(scope)
       parsewrap do
-        if (var = scope.lookupvar(@value, false)) == :undefined
+        if (var = scope.lookupvar(@value)) == :undefined
           var = :undef
         end
         var
diff --git a/lib/puppet/parser/functions/extlookup.rb b/lib/puppet/parser/functions/extlookup.rb
index b5688d644..5fbf26cec 100644
--- a/lib/puppet/parser/functions/extlookup.rb
+++ b/lib/puppet/parser/functions/extlookup.rb
@@ -91,9 +91,9 @@ This is for back compatibility to interpolate variables with %. % interpolation
 
   raise Puppet::ParseError, ("extlookup(): wrong number of arguments (#{args.length}; must be <= 3)") if args.length > 3
 
-  extlookup_datadir = lookupvar('::extlookup_datadir')
+  extlookup_datadir = undef_as('',lookupvar('::extlookup_datadir'))
 
-  extlookup_precedence = lookupvar('::extlookup_precedence').collect { |var| var.gsub(/%\{(.+?)\}/) { lookupvar("::#{$1}") } }
+  extlookup_precedence = undef_as([],lookupvar('::extlookup_precedence')).collect { |var| var.gsub(/%\{(.+?)\}/) { lookupvar("::#{$1}") } }
 
   datafiles = Array.new
 
diff --git a/lib/puppet/parser/resource.rb b/lib/puppet/parser/resource.rb
index c007d4dbe..ace01bb4b 100644
--- a/lib/puppet/parser/resource.rb
+++ b/lib/puppet/parser/resource.rb
@@ -241,7 +241,7 @@ class Puppet::Parser::Resource < Puppet::Resource
 
   def add_backward_compatible_relationship_param(name)
     # Skip metaparams for which we get no value.
-    return unless val = scope.lookupvar(name.to_s, false) and val != :undefined
+    return unless val = scope.lookupvar(name.to_s) and val != :undefined
 
     # The default case: just set the value
     set_parameter(name, val) and return unless @parameters[name]
diff --git a/lib/puppet/parser/scope.rb b/lib/puppet/parser/scope.rb
index 07347552b..df307915e 100644
--- a/lib/puppet/parser/scope.rb
+++ b/lib/puppet/parser/scope.rb
@@ -210,45 +210,41 @@ class Puppet::Parser::Scope
     find_definition(name) || find_hostclass(name)
   end
 
-  def lookup_qualified_var(name, usestring)
+  def undef_as(x,v)
+    (v == :undefined) ? x : (v == :undef) ? x : v
+  end
+
+  def lookup_qualified_var(name)
     parts = name.split(/::/)
     shortname = parts.pop
     klassname = parts.join("::")
     klass = find_hostclass(klassname)
     unless klass
       warning "Could not look up qualified variable '#{name}'; class #{klassname} could not be found"
-      return usestring ? "" : :undefined
+      return :undefined
     end
     unless kscope = class_scope(klass)
       warning "Could not look up qualified variable '#{name}'; class #{klassname} has not been evaluated"
-      return usestring ? "" : :undefined
+      return :undefined
     end
-    kscope.lookupvar(shortname, usestring)
+    kscope.lookupvar(shortname)
   end
 
   private :lookup_qualified_var
 
-  # Look up a variable.  The simplest value search we do.  Default to returning
-  # an empty string for missing values, but support returning a constant.
-  def lookupvar(name, usestring = true)
+  # Look up a variable.  The simplest value search we do.  
+  def lookupvar(name)
     table = ephemeral?(name) ? @ephemeral.last : @symtable
     # If the variable is qualified, then find the specified scope and look the variable up there instead.
     if name =~ /::/
-      return lookup_qualified_var(name, usestring)
-    end
-    # We can't use "if table[name]" here because the value might be false
-    if ephemeral_include?(name) or table.include?(name)
-      if usestring and table[name] == :undef
-        return ""
-      else
-        return table[name]
-      end
-    elsif self.parent
-      return parent.lookupvar(name, usestring)
-    elsif usestring
-      return ""
+      lookup_qualified_var(name)
+    elsif ephemeral_include?(name) or table.include?(name)
+      # We can't use "if table[name]" here because the value might be false
+      table[name]
+    elsif parent
+      parent.lookupvar(name)
     else
-      return :undefined
+      :undefined
     end
   end
 
@@ -333,7 +329,7 @@ class Puppet::Parser::Scope
       table[name] = value
     else # append case
       # lookup the value in the scope if it exists and insert the var
-      table[name] = lookupvar(name)
+      table[name] = undef_as('',lookupvar(name))
       # concatenate if string, append if array, nothing for other types
       case value
       when Array
@@ -363,7 +359,7 @@ class Puppet::Parser::Scope
           if var and var =~ /^[0-9]+$/ and not ephemeral_include?(var)
             next
           end
-          out << lookupvar(var).to_s || ""
+          out << undef_as('',lookupvar(var)).to_s
         end
       elsif ss.scan(/^\\(.)/)
         # Puppet.debug("Got escape: pos:%d; m:%s" % [ss.pos, ss.matched])
diff --git a/lib/puppet/parser/templatewrapper.rb b/lib/puppet/parser/templatewrapper.rb
index 6864aa1a9..73fcb8aac 100644
--- a/lib/puppet/parser/templatewrapper.rb
+++ b/lib/puppet/parser/templatewrapper.rb
@@ -20,11 +20,7 @@ class Puppet::Parser::TemplateWrapper
 
   # Should return true if a variable is defined, false if it is not
   def has_variable?(name)
-    if scope.lookupvar(name.to_s, false) != :undefined
-      true
-    else
-      false
-    end
+    scope.lookupvar(name.to_s) != :undefined
   end
 
   # Allow templates to access the defined classes
@@ -55,9 +51,7 @@ class Puppet::Parser::TemplateWrapper
   # the missing_method definition here until we declare the syntax finally
   # dead.
   def method_missing(name, *args)
-    # We have to tell lookupvar to return :undefined to us when
-    # appropriate; otherwise it converts to "".
-    value = scope.lookupvar(name.to_s, false)
+    value = scope.lookupvar(name.to_s)
     if value != :undefined
       return value
     else
diff --git a/spec/unit/parser/ast/arithmetic_operator_spec.rb b/spec/unit/parser/ast/arithmetic_operator_spec.rb
index 6f57fd9b6..0aab6f080 100755
--- a/spec/unit/parser/ast/arithmetic_operator_spec.rb
+++ b/spec/unit/parser/ast/arithmetic_operator_spec.rb
@@ -61,8 +61,8 @@ describe Puppet::Parser::AST::ArithmeticOperator do
   end
 
   it "should work for variables too" do
-    @scope.expects(:lookupvar).with("one", false).returns(1)
-    @scope.expects(:lookupvar).with("two", false).returns(2)
+    @scope.expects(:lookupvar).with("one").returns(1)
+    @scope.expects(:lookupvar).with("two").returns(2)
     one = ast::Variable.new( :value => "one" )
     two = ast::Variable.new( :value => "two" )
 
diff --git a/spec/unit/parser/ast/comparison_operator_spec.rb b/spec/unit/parser/ast/comparison_operator_spec.rb
index 169d92d0a..3efe28bb6 100755
--- a/spec/unit/parser/ast/comparison_operator_spec.rb
+++ b/spec/unit/parser/ast/comparison_operator_spec.rb
@@ -95,8 +95,8 @@ describe Puppet::Parser::AST::ComparisonOperator do
     one = Puppet::Parser::AST::Variable.new( :value => "one" )
     two = Puppet::Parser::AST::Variable.new( :value => "two" )
 
-    @scope.expects(:lookupvar).with("one", false).returns(1)
-    @scope.expects(:lookupvar).with("two", false).returns(2)
+    @scope.expects(:lookupvar).with("one").returns(1)
+    @scope.expects(:lookupvar).with("two").returns(2)
 
     operator = Puppet::Parser::AST::ComparisonOperator.new :lval => one, :operator => "<", :rval => two
     operator.evaluate(@scope).should == true
diff --git a/spec/unit/parser/ast/leaf_spec.rb b/spec/unit/parser/ast/leaf_spec.rb
index 3b8c14efa..97c996b40 100755
--- a/spec/unit/parser/ast/leaf_spec.rb
+++ b/spec/unit/parser/ast/leaf_spec.rb
@@ -336,12 +336,12 @@ describe Puppet::Parser::AST::Variable do
   end
 
   it "should lookup the variable in scope" do
-    @scope.expects(:lookupvar).with("myvar", false).returns(:myvalue)
+    @scope.expects(:lookupvar).with("myvar").returns(:myvalue)
     @var.safeevaluate(@scope).should == :myvalue
   end
 
   it "should return undef if the variable wasn't set" do
-    @scope.expects(:lookupvar).with("myvar", false).returns(:undefined)
+    @scope.expects(:lookupvar).with("myvar").returns(:undefined)
     @var.safeevaluate(@scope).should == :undef
   end
 
diff --git a/spec/unit/parser/scope_spec.rb b/spec/unit/parser/scope_spec.rb
index 44e255956..b37cb4add 100755
--- a/spec/unit/parser/scope_spec.rb
+++ b/spec/unit/parser/scope_spec.rb
@@ -76,16 +76,8 @@ describe Puppet::Parser::Scope do
   end
 
   describe "when looking up a variable" do
-    it "should default to an empty string" do
-      @scope.lookupvar("var").should == ""
-    end
-
-    it "should return an string when asked for a string" do
-      @scope.lookupvar("var", true).should == ""
-    end
-
-    it "should return ':undefined' for unset variables when asked not to return a string" do
-      @scope.lookupvar("var", false).should == :undefined
+    it "should return ':undefined' for unset variables" do
+      @scope.lookupvar("var").should == :undefined
     end
 
     it "should be able to look up values" do
@@ -151,32 +143,32 @@ describe Puppet::Parser::Scope do
         @scope.lookupvar("other::deep::klass::var").should == "otherval"
       end
 
-      it "should return an empty string for qualified variables that cannot be found in other classes" do
+      it "should return ':undefined' for qualified variables that cannot be found in other classes" do
         other_scope = create_class_scope("other::deep::klass")
 
-        @scope.lookupvar("other::deep::klass::var").should == ""
+        @scope.lookupvar("other::deep::klass::var").should == :undefined
       end
 
-      it "should warn and return an empty string for qualified variables whose classes have not been evaluated" do
+      it "should warn and return ':undefined' for qualified variables whose classes have not been evaluated" do
         klass = newclass("other::deep::klass")
         @scope.expects(:warning)
-        @scope.lookupvar("other::deep::klass::var").should == ""
+        @scope.lookupvar("other::deep::klass::var").should == :undefined
       end
 
-      it "should warn and return an empty string for qualified variables whose classes do not exist" do
+      it "should warn and return ':undefined' for qualified variables whose classes do not exist" do
         @scope.expects(:warning)
-        @scope.lookupvar("other::deep::klass::var").should == ""
+        @scope.lookupvar("other::deep::klass::var").should == :undefined
       end
 
       it "should return ':undefined' when asked for a non-string qualified variable from a class that does not exist" do
         @scope.stubs(:warning)
-        @scope.lookupvar("other::deep::klass::var", false).should == :undefined
+        @scope.lookupvar("other::deep::klass::var").should == :undefined
       end
 
       it "should return ':undefined' when asked for a non-string qualified variable from a class that has not been evaluated" do
         @scope.stubs(:warning)
         klass = newclass("other::deep::klass")
-        @scope.lookupvar("other::deep::klass::var", false).should == :undefined
+        @scope.lookupvar("other::deep::klass::var").should == :undefined
       end
     end
   end
@@ -291,7 +283,7 @@ describe Puppet::Parser::Scope do
 
       @scope.unset_ephemeral_var
 
-      @scope.lookupvar("1", false).should == :undefined
+      @scope.lookupvar("1").should == :undefined
     end
 
     it "should not remove classic variables when unset_ephemeral_var is called" do
@@ -301,7 +293,7 @@ describe Puppet::Parser::Scope do
 
       @scope.unset_ephemeral_var
 
-      @scope.lookupvar("myvar", false).should == :value1
+      @scope.lookupvar("myvar").should == :value1
     end
 
     it "should raise an error when setting it again" do
@@ -322,7 +314,7 @@ describe Puppet::Parser::Scope do
         @scope.setvar("0", :earliest, :ephemeral => true)
         @scope.new_ephemeral
         @scope.setvar("0", :latest, :ephemeral => true)
-        @scope.lookupvar("0", false).should == :latest
+        @scope.lookupvar("0").should == :latest
       end
 
       it "should be able to report the current level" do
@@ -353,7 +345,7 @@ describe Puppet::Parser::Scope do
         @scope.setvar("1", :value1, :ephemeral => true)
         @scope.new_ephemeral
         @scope.setvar("0", :value2, :ephemeral => true)
-        @scope.lookupvar("1", false).should == :value1
+        @scope.lookupvar("1").should == :value1
       end
 
       describe "when calling unset_ephemeral_var without a level" do
@@ -364,7 +356,7 @@ describe Puppet::Parser::Scope do
 
           @scope.unset_ephemeral_var
 
-          @scope.lookupvar("1", false).should == :undefined
+          @scope.lookupvar("1").should == :undefined
         end
       end
 
@@ -378,7 +370,7 @@ describe Puppet::Parser::Scope do
 
           @scope.unset_ephemeral_var(2)
 
-          @scope.lookupvar("1", false).should == :value2
+          @scope.lookupvar("1").should == :value2
         end
       end
     end
@@ -563,13 +555,13 @@ describe Puppet::Parser::Scope do
     it "should be able to unset normal variables" do
       @scope.setvar("foo", "bar")
       @scope.unsetvar("foo")
-      @scope.lookupvar("foo").should == ""
+      @scope.lookupvar("foo").should == :undefined
     end
 
     it "should be able to unset ephemeral variables" do
       @scope.setvar("0", "bar", :ephemeral => true)
       @scope.unsetvar("0")
-      @scope.lookupvar("0").should == ""
+      @scope.lookupvar("0").should == :undefined
     end
 
     it "should not unset ephemeral variables in previous ephemeral scope" do
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
diff --git a/test/language/functions.rb b/test/language/functions.rb
index e882b68f3..84b1b3861 100755
--- a/test/language/functions.rb
+++ b/test/language/functions.rb
@@ -382,17 +382,15 @@ class TestLangFunctions < Test::Unit::TestCase
     }.each do |string, value|
       scope = mkscope
       scope.setvar("yayness", string)
-      assert_equal(string, scope.lookupvar("yayness", false))
+      assert_equal(string, scope.lookupvar("yayness"))
 
       assert_nothing_raised("An empty string was not a valid variable value") do
         ast.evaluate(scope)
       end
 
-
-        assert_equal(
-          "template #{value}\n", scope.lookupvar("output"),
-
-            "#{string.inspect} did not get evaluated correctly")
+      assert_equal(
+        "template #{value}\n", scope.lookupvar("output"),
+        "#{string.inspect} did not get evaluated correctly")
     end
   end
 
diff --git a/test/language/scope.rb b/test/language/scope.rb
index c4154dc27..ccc359651 100755
--- a/test/language/scope.rb
+++ b/test/language/scope.rb
@@ -42,22 +42,22 @@ class TestScope < Test::Unit::TestCase
     # Set a variable in the top and make sure all three can get it
     topscope.setvar("first", "topval")
     scopes.each do |name, scope|
-      assert_equal("topval", scope.lookupvar("first", false), "Could not find var in #{name}")
+      assert_equal("topval", scope.lookupvar("first"), "Could not find var in #{name}")
     end
 
     # Now set a var in the midscope and make sure the mid and bottom can see it but not the top
     midscope.setvar("second", "midval")
-    assert_equal(:undefined, scopes[:top].lookupvar("second", false), "Found child var in top scope")
+    assert_equal(:undefined, scopes[:top].lookupvar("second"), "Found child var in top scope")
     [:mid, :bot].each do |name|
-      assert_equal("midval", scopes[name].lookupvar("second", false), "Could not find var in #{name}")
+      assert_equal("midval", scopes[name].lookupvar("second"), "Could not find var in #{name}")
     end
 
     # And set something in the bottom, and make sure we only find it there.
     botscope.setvar("third", "botval")
     [:top, :mid].each do |name|
-      assert_equal(:undefined, scopes[name].lookupvar("third", false), "Found child var in top scope")
+      assert_equal(:undefined, scopes[name].lookupvar("third"), "Found child var in top scope")
     end
-    assert_equal("botval", scopes[:bot].lookupvar("third", false), "Could not find var in bottom scope")
+    assert_equal("botval", scopes[:bot].lookupvar("third"), "Could not find var in bottom scope")
 
 
     # Test that the scopes convert to hash structures correctly.
@@ -260,18 +260,7 @@ Host <<||>>"
     scope = mkscope
 
     scope.setvar("testing", :undef)
-
-
-      assert_equal(
-        :undef, scope.lookupvar("testing", false),
-
-      "undef was not returned as :undef when not string")
-
-
-        assert_equal(
-          "", scope.lookupvar("testing", true),
-
-      "undef was not returned as '' when string")
+    assert_equal(:undef, scope.lookupvar("testing"), "undef was not returned as :undef")
   end
 end