fix idempotency for empty environment

lib/puppet/provider/cron/crontab.rb

@@ -221,7 +221,7 @@ def self.prefetch_hook(records)
           record[:unmanaged] = true
         end
         if envs.nil? || envs.empty?
-          record[:environment] = :absent
+          record[:environment] = []
         else
           # Collect all of the environment lines, and mark the records to be skipped,
           # since their data is included in our crontab record.

spec/acceptance/tests/resource/cron/should_be_idempotent_spec.rb

@@ -18,14 +18,14 @@
   compatible_agents.each do |agent|
     it "ensures idempotency on #{agent}" do
       step 'Cron: basic - verify that it can be created'
-      result = apply_manifest_on(agent, 'cron { "myjob": command => "/bin/true", user    => "tstuser", hour    => "*", minute  => [1], ensure  => present,}')
+      result = apply_manifest_on(agent, 'cron { "myjob": command => "/bin/true", user    => "tstuser", hour    => "*", minute  => [1], ensure  => present, environment => [],}')
       expect(result.stdout).to match(%r{ensure: created})
 
       result = run_cron_on(agent, :list, 'tstuser')
       expect(result.stdout).to match(%r{. . . . . .bin.true})
 
       step 'Cron: basic - should not create again'
-      result = apply_manifest_on(agent, 'cron { "myjob": command => "/bin/true", user    => "tstuser", hour    => "*", minute  => [1], ensure  => present,}')
+      result = apply_manifest_on(agent, 'cron { "myjob": command => "/bin/true", user    => "tstuser", hour    => "*", minute  => [1], ensure  => present, environment => [],}')
       expect(result.stdout).not_to match(%r{ensure: created})
     end
   end

spec/unit/provider/cron/parsed_spec.rb

@@ -223,7 +223,7 @@
         expect(parameters[0][:special]).to eq(:absent)
         expect(parameters[0][:command]).to match(%r{\$HOME/bin/daily.job >> \$HOME/tmp/out 2>&1})
         expect(parameters[0][:ensure]).to eq(:present)
-        expect(parameters[0][:environment]).to eq(:absent)
+        expect(parameters[0][:environment]).to eq([])
         expect(parameters[0][:user]).to eq(:absent)
 
         expect(parameters[1][:name]).to match(%r{unmanaged:\$HOME/bin/monthly-\d+})
@@ -235,7 +235,7 @@
         expect(parameters[1][:special]).to eq(:absent)
         expect(parameters[1][:command]).to match(%r{\$HOME/bin/monthly})
         expect(parameters[1][:ensure]).to eq(:present)
-        expect(parameters[1][:environment]).to eq(:absent)
+        expect(parameters[1][:environment]).to eq([])
         expect(parameters[1][:user]).to eq(:absent)
         expect(parameters[1][:target]).to eq('foobar')
       end
@@ -259,7 +259,7 @@
                        special: :absent,
                        command: '/bin/true',
                        ensure: :present,
-                       environment: :absent,
+                       environment: [],
                        user: :absent,
                        target: 'foobar',
                      },