Fix #2033 - Allow regexp in if expression

This changeset introduces regexp in if expression with the use of the
=~ (match) and !~ (not match) operator.

Usage:

if $uname =~ /Linux|Debian/ {
  ...
}

Moreover this patch creates ephemeral variables ($0 to $9) in the current
scope which contains the regex captures:
if $uname =~ /(Linux|Debian)/ {
  notice("this is a $1 system")
}

Signed-off-by: Brice Figureau <brice-puppet@daysofwonder.com>

2 files changed, 42 insertions, 6 deletions

diff --git a/lib/puppet/parser/ast/ifstatement.rb b/lib/puppet/parser/ast/ifstatement.rb
index d216b7c65..9d52123b6 100644
--- a/lib/puppet/parser/ast/ifstatement.rb
+++ b/lib/puppet/parser/ast/ifstatement.rb
@@ -18,14 +18,19 @@ class Puppet::Parser::AST
         def evaluate(scope)
             value = @test.safeevaluate(scope)
 
-            if Puppet::Parser::Scope.true?(value)
-                return @statements.safeevaluate(scope)
-            else
-                if defined? @else
-                    return @else.safeevaluate(scope)
+            # let's emulate a new scope for each branches
+            begin
+                if Puppet::Parser::Scope.true?(value)
+                    return @statements.safeevaluate(scope)
                 else
-                    return nil
+                    if defined? @else
+                        return @else.safeevaluate(scope)
+                    else
+                        return nil
+                    end
                 end
+            ensure
+                scope.unset_ephemeral_var
             end
         end
     end
diff --git a/lib/puppet/parser/ast/match_operator.rb b/lib/puppet/parser/ast/match_operator.rb
new file mode 100644
index 000000000..17e27826e
--- /dev/null
+++ b/lib/puppet/parser/ast/match_operator.rb
@@ -0,0 +1,31 @@
+require 'puppet'
+require 'puppet/parser/ast/branch'
+
+class Puppet::Parser::AST
+    class MatchOperator < AST::Branch
+
+        attr_accessor :lval, :rval, :operator
+
+        # Iterate across all of our children.
+        def each
+            [@lval,@rval].each { |child| yield child }
+        end
+
+        # Returns a boolean which is the result of the boolean operation
+        # of lval and rval operands
+        def evaluate(scope)
+            lval = @lval.safeevaluate(scope)
+
+            return @operator == "=~" if rval.evaluate_match(lval, scope)
+            return @operator == "!~"
+        end
+
+        def initialize(hash)
+            super
+
+            unless %w{!~ =~}.include?(@operator)
+                raise ArgumentError, "Invalid regexp operator %s" % @operator
+            end
+        end
+    end
+end