[#4370] Fixes extlookup precedence getting overwritten between runs

We found the gsub! in extlookup was actually modifying the value for
extlookup_precedence, so the next node to call it just got the
interpolated value from the first run.

We did two things in the code to prevent this:
1. We returned a dup of the ast string object so that modifying it
wouldn’t change puppet’s state. We didn’t do this for all possible
return values because we depend on using the original ast array object
to do array concatenation
2. We fixed extlookup to not do a destructive gsub

Reviewed by: Jesse Wolfe

3 files changed, 7 insertions, 12 deletions

diff --git a/lib/puppet/parser/ast/function.rb b/lib/puppet/parser/ast/function.rb
index 602016c75..74023f631 100644
--- a/lib/puppet/parser/ast/function.rb
+++ b/lib/puppet/parser/ast/function.rb
@@ -11,7 +11,6 @@ class Puppet::Parser::AST
     @settor = true
 
     def evaluate(scope)
-
       # Make sure it's a defined function
       raise Puppet::ParseError, "Unknown function #{@name}" unless Puppet::Parser::Functions.function(@name)
 
diff --git a/lib/puppet/parser/ast/leaf.rb b/lib/puppet/parser/ast/leaf.rb
index 49cde63ca..090d75c4e 100644
--- a/lib/puppet/parser/ast/leaf.rb
+++ b/lib/puppet/parser/ast/leaf.rb
@@ -42,7 +42,7 @@ class Puppet::Parser::AST
   # The base string class.
   class String < AST::Leaf
     def evaluate(scope)
-      @value
+      @value.dup
     end
 
     def to_s
diff --git a/lib/puppet/parser/functions/extlookup.rb b/lib/puppet/parser/functions/extlookup.rb
index ee230e7ce..177d9aef8 100644
--- a/lib/puppet/parser/functions/extlookup.rb
+++ b/lib/puppet/parser/functions/extlookup.rb
@@ -99,19 +99,15 @@ module Puppet::Parser::Functions
     # this will result in /path/to/extdata/hosts/your.box.com.csv
     # being searched.
     #
-    # we parse the precedence here because the best place to specify
-    # it would be in site.pp but site.pp is only evaluated at startup
-    # so $fqdn etc would have no meaning there, this way it gets evaluated
-    # each run and has access to the right variables for that run
-    lookupvar('extlookup_precedence').each do |prec|
-      while prec =~ /%\{(.+?)\}/
-        prec.gsub!(/%\{#{$1}\}/, lookupvar($1))
+    # This is for back compatibility to interpolate variables with %.
+    # % interpolation is a workaround for a problem that has been fixed: Puppet variable
+    # interpolation at top scope used to only happen on each run
+    extlookup_precedence = lookupvar('extlookup_precedence').collect do |var|
+      var.gsub(/%\{(.+?)\}/) do |capture|
+        lookupvar($1)
       end
-
-      extlookup_precedence << prec
     end
 
-
     datafiles = Array.new
 
     # if we got a custom data file, put it first in the array of search files