Fix #3155 - prevent error when using two matching regex in cascade

The following manifest:
case $var {
  /match/: {
     if $var =~ /matchagain/ {
     }
  }
}

is failing because the "=~" operators when matching sets an ephemeral
variable in the scope. But the case regex also did it, and since they
both belong to the same scope, and Puppet variables are immutables, the
scope raises an error.

This patch fixes this issue by adding to the current scope a stack
of ephemeral symbol tables. Each new match operator or case/selector
with regex adds a new scope. When we get out of the case/if/selector
structure the scope is reset to the ephemeral level we were when
entering it.

This way the following manifest produces the correct output:
case $var {
  /match(rematch)/: {
     notice("1. \$0 = $0, \$1 = $1")
     if $var =~ /matchagain/ {
         notice("2. \$0 = $0, \$1 = $1")
     }
     notice("3. \$0 = $0, \$1 = $1")
  }
}
notice("4. \$0 = $0")

And the output is:
1. $0 = match, $1 = rematch
2. $0 = matchagain, $1 = rematch
3. $0 = match, $1 = rematch
4. $0 =

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

4 files changed, 104 insertions, 8 deletions

diff --git a/spec/unit/parser/ast/casestatement.rb b/spec/unit/parser/ast/casestatement.rb
index c2e9a6929..240d3bfea 100755
--- a/spec/unit/parser/ast/casestatement.rb
+++ b/spec/unit/parser/ast/casestatement.rb
@@ -104,19 +104,21 @@ describe Puppet::Parser::AST::CaseStatement do
             end
 
             it "should unset scope ephemeral variables after option evaluation" do
+                @scope.stubs(:ephemeral_level).returns(:level)
                 @opval1.stubs(:evaluate_match).with { |*arg| arg[0] == "value" and arg[1] == @scope }.returns(true)
                 @option1.stubs(:safeevaluate).with(@scope).returns(:result)
 
-                @scope.expects(:unset_ephemeral_var)
+                @scope.expects(:unset_ephemeral_var).with(:level)
 
                 @casestmt.evaluate(@scope)
             end
 
             it "should not leak ephemeral variables even if evaluation fails" do
+                @scope.stubs(:ephemeral_level).returns(:level)
                 @opval1.stubs(:evaluate_match).with { |*arg| arg[0] == "value" and arg[1] == @scope }.returns(true)
                 @option1.stubs(:safeevaluate).with(@scope).raises
 
-                @scope.expects(:unset_ephemeral_var)
+                @scope.expects(:unset_ephemeral_var).with(:level)
 
                 lambda { @casestmt.evaluate(@scope) }.should raise_error
             end
diff --git a/spec/unit/parser/ast/ifstatement.rb b/spec/unit/parser/ast/ifstatement.rb
index 10d877a4b..83121cddd 100755
--- a/spec/unit/parser/ast/ifstatement.rb
+++ b/spec/unit/parser/ast/ifstatement.rb
@@ -64,10 +64,11 @@ describe Puppet::Parser::AST::IfStatement do
         end
 
         it "should reset ephemeral statements after evaluation" do
+            @scope.expects(:ephemeral_level).returns(:level)
             Puppet::Parser::Scope.stubs(:true?).returns(true)
 
             @stmt.expects(:safeevaluate).with(@scope)
-            @scope.expects(:unset_ephemeral_var)
+            @scope.expects(:unset_ephemeral_var).with(:level)
 
             @ifstmt.evaluate(@scope)
         end
diff --git a/spec/unit/parser/ast/selector.rb b/spec/unit/parser/ast/selector.rb
index 23989b902..f32310b92 100755
--- a/spec/unit/parser/ast/selector.rb
+++ b/spec/unit/parser/ast/selector.rb
@@ -102,19 +102,21 @@ describe Puppet::Parser::AST::Selector do
             end
 
             it "should unset scope ephemeral variables after option evaluation" do
+                @scope.stubs(:ephemeral_level).returns(:level)
                 @param1.stubs(:evaluate_match).with { |*arg| arg[0] == "value" and arg[1] == @scope }.returns(true)
                 @value1.stubs(:safeevaluate).with(@scope).returns(:result)
 
-                @scope.expects(:unset_ephemeral_var)
+                @scope.expects(:unset_ephemeral_var).with(:level)
 
                 @selector.evaluate(@scope)
             end
 
             it "should not leak ephemeral variables even if evaluation fails" do
+                @scope.stubs(:ephemeral_level).returns(:level)
                 @param1.stubs(:evaluate_match).with { |*arg| arg[0] == "value" and arg[1] == @scope }.returns(true)
                 @value1.stubs(:safeevaluate).with(@scope).raises
 
-                @scope.expects(:unset_ephemeral_var)
+                @scope.expects(:unset_ephemeral_var).with(:level)
 
                 lambda { @selector.evaluate(@scope) }.should raise_error
             end
diff --git a/spec/unit/parser/scope.rb b/spec/unit/parser/scope.rb
index 56bcd18fb..c030f2552 100755
--- a/spec/unit/parser/scope.rb
+++ b/spec/unit/parser/scope.rb
@@ -286,6 +286,85 @@ describe Puppet::Parser::Scope do
 
             @scope.lookupvar("myvar", false).should == :value1
         end
+
+        it "should raise an error when setting it again" do
+            @scope.setvar("1", :value2, :ephemeral => true)
+            lambda { @scope.setvar("1", :value3, :ephemeral => true) }.should raise_error
+        end
+
+        it "should declare ephemeral number only variable names" do
+            @scope.ephemeral?("0").should be_true
+        end
+
+        it "should not declare ephemeral other variable names" do
+            @scope.ephemeral?("abc0").should be_nil
+        end
+
+        describe "with more than one level" do
+            it "should prefer latest ephemeral scopes" do
+                @scope.setvar("0", :earliest, :ephemeral => true)
+                @scope.new_ephemeral
+                @scope.setvar("0", :latest, :ephemeral => true)
+                @scope.lookupvar("0", false).should == :latest
+            end
+
+            it "should be able to report the current level" do
+                @scope.ephemeral_level.should == 1
+                @scope.new_ephemeral
+                @scope.ephemeral_level.should == 2
+            end
+
+            it "should check presence of an ephemeral variable accross multiple levels" do
+                @scope.new_ephemeral
+                @scope.setvar("1", :value1, :ephemeral => true)
+                @scope.new_ephemeral
+                @scope.setvar("0", :value2, :ephemeral => true)
+                @scope.new_ephemeral
+                @scope.ephemeral_include?("1").should be_true
+            end
+
+            it "should return false when an ephemeral variable doesn't exist in any ephemeral scope" do
+                @scope.new_ephemeral
+                @scope.setvar("1", :value1, :ephemeral => true)
+                @scope.new_ephemeral
+                @scope.setvar("0", :value2, :ephemeral => true)
+                @scope.new_ephemeral
+                @scope.ephemeral_include?("2").should be_false
+            end
+
+            it "should get ephemeral values from earlier scope when not in later" do
+                @scope.setvar("1", :value1, :ephemeral => true)
+                @scope.new_ephemeral
+                @scope.setvar("0", :value2, :ephemeral => true)
+                @scope.lookupvar("1", false).should == :value1
+            end
+
+            describe "when calling unset_ephemeral_var without a level" do
+                it "should remove all the variables values"  do
+                    @scope.setvar("1", :value1, :ephemeral => true)
+                    @scope.new_ephemeral
+                    @scope.setvar("1", :value2, :ephemeral => true)
+
+                    @scope.unset_ephemeral_var
+
+                    @scope.lookupvar("1", false).should == :undefined
+                end
+            end
+
+            describe "when calling unset_ephemeral_var with a level" do
+                it "should remove ephemeral scopes up to this level" do
+                    @scope.setvar("1", :value1, :ephemeral => true)
+                    @scope.new_ephemeral
+                    @scope.setvar("1", :value2, :ephemeral => true)
+                    @scope.new_ephemeral
+                    @scope.setvar("1", :value3, :ephemeral => true)
+
+                    @scope.unset_ephemeral_var(2)
+
+                    @scope.lookupvar("1", false).should == :value2
+                end
+            end
+        end
     end
 
     describe "when interpolating string" do
@@ -451,6 +530,11 @@ describe Puppet::Parser::Scope do
 
             @scope.ephemeral_from(@match)
         end
+
+        it "should create a new ephemeral level" do
+            @scope.expects(:new_ephemeral)
+            @scope.ephemeral_from(@match)
+        end
     end
 
     describe "when unsetting variables" do
@@ -461,9 +545,16 @@ describe Puppet::Parser::Scope do
         end
 
         it "should be able to unset ephemeral variables" do
-            @scope.setvar("foo", "bar", :ephemeral => true)
-            @scope.unsetvar("foo")
-            @scope.lookupvar("foo").should == ""
+            @scope.setvar("0", "bar", :ephemeral => true)
+            @scope.unsetvar("0")
+            @scope.lookupvar("0").should == ""
+        end
+
+        it "should not unset ephemeral variables in previous ephemeral scope" do
+            @scope.setvar("0", "bar", :ephemeral => true)
+            @scope.new_ephemeral
+            @scope.unsetvar("0")
+            @scope.lookupvar("0").should == "bar"
         end
     end