(FACT-2699) augeas fact for OSX is not resolved

lib/facter/resolvers/augeas_resolver.rb

@@ -14,10 +14,27 @@ def post_resolve(fact_name)
         end
 
         def read_augeas_version(fact_name)
-          output = Facter::Core::Execution.execute('augparse --version 2>&1', logger: log)
-          @fact_list[:augeas_version] = Regexp.last_match(1) if output =~ /^augparse (\d+\.\d+\.\d+)/
+          @fact_list[:augeas_version] = read_augeas_from_cli
+          @fact_list[:augeas_version] ||= read_augeas_from_gem
+
           @fact_list[fact_name]
         end
+
+        def read_augeas_from_cli
+          output = Facter::Core::Execution.execute('augparse --version 2>&1', logger: log)
+          Regexp.last_match(1) if output =~ /^augparse (\d+\.\d+\.\d+)/
+        end
+
+        def read_augeas_from_gem
+          require 'augeas'
+
+          if Gem.loaded_specs['augeas']
+            ::Augeas.create { |aug| aug.get('/augeas/version') }
+          else
+            # it is used for legacy augeas <= 0.5.0 (ruby-augeas gem)
+            ::Augeas.open { |aug| aug.get('/augeas/version') }
+          end
+        end
       end
     end
   end

spec/facter/resolvers/augeas_resolver_spec.rb

@@ -7,12 +7,65 @@
 
   before do
     augeas.instance_variable_set(:@log, log_spy)
-    allow(Facter::Core::Execution).to receive(:execute)
-      .with('augparse --version 2>&1', logger: log_spy)
-      .and_return('augparse 1.12.0 <http://augeas.net/>')
   end
 
-  it 'returns build' do
-    expect(augeas.resolve(:augeas_version)).to eq('1.12.0')
+  after do
+    augeas.invalidate_cache
+  end
+
+  context 'when augparse is installed' do
+    before do
+      allow(Facter::Core::Execution).to receive(:execute)
+        .with('augparse --version 2>&1', logger: log_spy)
+        .and_return('augparse 1.12.0 <http://augeas.net/>')
+    end
+
+    it 'returns build' do
+      expect(augeas.resolve(:augeas_version)).to eq('1.12.0')
+    end
+  end
+
+  context 'when augparse is not installed' do
+    before do
+      allow(Facter::Core::Execution).to receive(:execute)
+        .with('augparse --version 2>&1', logger: log_spy)
+        .and_return('sh: augparse: command not found')
+    end
+
+    context 'when augeas gem > 0.5.0 is installed' do
+      before do
+        allow(Gem).to receive(:loaded_specs).and_return({ 'augeas' => true })
+        allow(Augeas).to receive(:create).and_return('1.12.0')
+      end
+
+      it 'returns build' do
+        expect(augeas.resolve(:augeas_version)).to eq('1.12.0')
+      end
+    end
+
+    context 'when augeas gem <= 0.5.0 is installed' do
+      before do
+        allow(Gem).to receive(:loaded_specs).and_return({})
+        allow(Augeas).to receive(:open).and_return('1.12.0')
+      end
+
+      it 'returns build' do
+        expect(augeas.resolve(:augeas_version)).to eq('1.12.0')
+      end
+    end
+
+    context 'when augeas gem is not installed' do
+      let(:exception) { LoadError.new('load_error_message') }
+
+      before do
+        allow(Facter::Resolvers::Augeas).to receive(:require).with('augeas').and_raise(exception)
+      end
+
+      it 'raises a LoadError error' do
+        augeas.resolve(:augeas_version)
+
+        expect(log_spy).to have_received(:debug).with('resolving fact augeas_version, but load_error_message')
+      end
+    end
   end
 end

spec/mocks/augeas.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class Augeas
+  def self.create(opts = {}, &block); end
+
+  def self.open(root = nil, loadpath = nil, flags = NONE, &block); end
+end

spec/mocks/kernel_mock.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-LIBS_TO_SKIP = %w[win32ole ffi win32/registry sys/filesystem].freeze
+LIBS_TO_SKIP = %w[win32ole ffi win32/registry sys/filesystem augeas].freeze
 module Kernel
   alias old_require require
   def require(path)