Evaluate confine block in case-insensitive way

Prior to this commit when a user provided a confine block, Facter would
downcase the value when evaluating it.

For example:

confine :kernel do |value|
  value == "Linux"
end

While Facter's public documentation states that this is a valid way to
write a confine block, it would incorrectly and unexpectedly evaluate
as false on Linux systems.

However, these other styles of confine would return true:

confine :kernel => "Linux"

confine kernel: "Linux"

This downcasing behavior was introduced in 7a81945 as a way of comparing
values in a case-insensitive way. However when block confines were
introduced in e4c8689, it added block evaluation before value
comparison, making the case-insensitive comparison moot with blocks.

This commit retains existing behavior of evaluating a confine block with
a downcased fact value, while adding evaluation with the raw fact value
to ensure expected behavior.

Author: mhashizume

lib/facter/custom_facts/util/confine.rb

@@ -35,7 +35,7 @@ def to_s
       end
 
       # Evaluate the fact, returning true or false.
-      # if we have a block paramter then we only evaluate that instead
+      # if we have a block parameter then we only evaluate that instead
       def true?
         if @block && !@fact
           begin
@@ -54,9 +54,11 @@ def true?
 
         return false if value.nil?
 
+        # We call the block with both the downcased and raw fact value for
+        # backwards-compatibility.
         if @block
           begin
-            return !!@block.call(value)
+            return !@block.call(value).nil? || !@block.call(fact.value).nil?
           rescue StandardError => e
             log.debug "Confine raised #{e.class} #{e}"
             return false

spec/custom_facts/util/confine_spec.rb

@@ -126,6 +126,12 @@ def confined(fact_value, *confines)
       expect(confine.true?).to be true
     end
 
+    it 'accepts and evaluate a block argument against the fact while respecting case' do
+      allow(fact).to receive(:value).and_return 'Foo'
+      confine = LegacyFacter::Util::Confine.new(:yay) { |f| f == 'Foo' }
+      expect(confine.true?).to be true
+    end
+
     it 'returns false if the block raises a StandardError when checking a fact' do
       allow(fact).to receive(:value).and_return 'foo'
       confine = LegacyFacter::Util::Confine.new(:yay) { |_f| raise StandardError }