(FACT-2317) Add Facter.define_fact method

lib/facter.rb

@@ -102,6 +102,19 @@ def debugonce(message)
       nil
     end
 
+    # Define a new fact or extend an existing fact.
+    #
+    # @param name [Symbol] The name of the fact to define
+    # @param options [Hash] A hash of options to set on the fact
+    #
+    # @return [Facter::Util::Fact] The fact that was defined
+    #
+    # @api public
+    def define_fact(name, options = {}, &block)
+      options[:fact_type] = :custom
+      LegacyFacter.define_fact(name, options, &block)
+    end
+
     def on_message(&block)
       Facter::Log.on_message(&block)
     end

spec/facter/facter_spec.rb

@@ -296,6 +296,16 @@ def mock_collection(method, os_name = nil, error = nil)
     end
   end
 
+  describe '#define_fact' do
+    it 'sends call to LegacyFacter' do
+      allow(LegacyFacter).to receive(:define_fact)
+
+      Facter.define_fact('fact_name') {}
+
+      expect(LegacyFacter).to have_received(:define_fact).once.with('fact_name', { fact_type: :custom })
+    end
+  end
+
   describe '#trace?' do
     it 'returns trace variable' do
       expect(Facter).not_to be_trace