(FACT-2086) Use core facts when weight is 0 for custom facts (#118)

* (FACT-2086) Fix Facter interface for add method.
* (FACT-2086) Add test for empty resolved fact list in hocon formatter.
* (FACT-2086) Take into account weight when deciding between custom facts and core facts.
* (FACT-2086) Add tests for fact and collection.

.rubocop.yml

@@ -70,6 +70,7 @@ Metrics/ClassLength:
   Exclude:
     - 'lib/custom_facts/util/fact.rb'
     - 'lib/resolvers/windows/networking_resolver.rb'
+    - 'lib/custom_facts/util/collection.rb'
 
 Style/DoubleNegation:
   Exclude:

custom_facts/my_custom_fact.rb

@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-LegacyFacter.add(:my_custom_fact) do
+Facter.add(:my_custom_fact) do
   has_weight(10_000)
   setcode do
     # 'my_custom_fact'
-    LegacyFacter.value('os')
+    Facter.value('os')
   end
 end

lib/custom_facts/util/collection.rb

@@ -137,9 +137,16 @@ def to_hash
 
       def value(name)
         fact = fact(name)
+
         return Facter.core_value(name) if fact.nil?
 
-        fact&.value
+        value = fact&.value
+        weight = fact&.used_resolution_weight || 0
+
+        core_value = Facter.core_value(name)
+        return core_value if weight <= 0 && core_value
+
+        value
       end
 
       private

lib/custom_facts/util/fact.rb

@@ -17,6 +17,8 @@ class Fact
       # @deprecated
       attr_accessor :ldapname
 
+      attr_accessor :used_resolution_weight
+
       # Creates a new fact, with no resolution mechanisms. See {Facter.add}
       # for the public API for creating facts.
       # @param name [String] the fact name
@@ -158,6 +160,7 @@ def sort_by_weight(resolutions)
       def find_first_real_value(resolutions)
         resolutions.each do |resolve|
           value = resolve.value
+          @used_resolution_weight = resolve.weight
           return value unless value.nil?
         end
         nil

lib/custom_facts/util/resolution.rb

@@ -16,6 +16,8 @@ class Resolution
       attr_accessor :code
       attr_writer :value
 
+      attr_reader :weight
+
       extend LegacyFacter::Core::Execution
 
       class << self

lib/facter-ng.rb

@@ -26,11 +26,12 @@ def self.value(user_query)
     fact_collection.dig(*user_query.split('.'))
   end
 
-  def add(name, options = {}, &block)
+  def self.add(name, options = {}, &block)
     LegacyFacter.add(name, options, &block)
   end
 
   def self.core_value(user_query)
+    user_query = user_query.to_s
     resolved_facts = Facter::FactManager.instance.resolve_core({}, [user_query])
     fact_collection = FactCollection.new.build_fact_collection!(resolved_facts)
     fact_collection.dig(*user_query.split('.'))

spec/custom_facts/util/collection_spec.rb

@@ -132,8 +132,34 @@
     it 'should treat strings and symbols equivalently' do
       expect(collection.value(:yayness)).to eq 'result'
     end
+
+    describe 'when the fact is a core fact' do
+      it 'should call the core_value method' do
+        expect(Facter).to receive(:core_value).with('core_fact')
+        collection.value('core_fact')
+      end
+    end
+
+    describe 'when the weight of the resolution is 0' do
+      it 'should return core facts value is it exists' do
+        expect(Facter).to receive(:core_value).with('yayness').and_return('core_result')
+        expect(collection.value('yayness')).to eq('core_result')
+      end
+    end
+
+    describe 'when the weight of the resolution is greater than 0' do
+      it 'shoudl return the custom fact value' do
+        expect(collection.value('yayness')).to eq('result')
+      end
+    end
   end
 
+  # describe 'when retriving a core fact' do
+  #   before do
+  #     # @fact = collection.add('YayNess', value: 'result')
+  #   end
+  # end
+
   it "should return the fact's value when the array index method is used" do
     collection.add('myfact', value: 'foo')
 

spec/custom_facts/util/fact_spec.rb

@@ -149,6 +149,26 @@ def suitable?
 
       expect(fact.value).to eq '1'
     end
+
+    it 'sets weight of the resolution that gave the value' do
+      fact.add do
+        has_weight 1
+        setcode { '1' }
+      end
+
+      fact.add do
+        has_weight 2
+        setcode { nil }
+      end
+
+      fact.add do
+        has_weight 0
+        setcode { '0' }
+      end
+
+      expect(fact.value).to eq '1'
+      expect(fact.used_resolution_weight).to eq 1
+    end
   end
 
   describe '#flush' do

spec/framework/formatters/hocon_fact_formatter_spec.rb

@@ -40,4 +40,10 @@
 
     expect(formatted_output).to eq(expected_output)
   end
+
+  it 'formats to hocon for empty resolved fact array' do
+    formatted_output = Facter::HoconFactFormatter.new.format([])
+
+    expect(formatted_output).to eq(nil)
+  end
 end