Fix cron resource commented job handling

This change fixes an edge case failure that may occur when processing a
cron resource where the following conditions are true:

* A `# Chef Name` comment exists for the job
* The following line is commented out
* The new cron resource uses default values for the minute, hour, day,
month, weekday, and time properties

This causes the following error to be raised within the
`Chef::Provider::Cron#cron_different?` method:

```
  Chef::Exceptions::ValidationFailed
  ----------------------------------
  command is a required property
```

The new guard prevents `cron_different?` from being called when the
current resource does not have a set command property. Since the new
resource requires the command property to be set to be valid, we can
assume it is different from the current cron resource if the command is
unset.

Signed-off-by: Matthew Newell <18470637+wheatevo@users.noreply.github.com>

2 files changed, 49 insertions, 1 deletions

diff --git a/lib/chef/provider/cron.rb b/lib/chef/provider/cron.rb
index 77c1973fb4..694f7ba4b8 100644
--- a/lib/chef/provider/cron.rb
+++ b/lib/chef/provider/cron.rb
@@ -100,7 +100,10 @@ class Chef
         newcron = get_crontab_entry
 
         if @cron_exists
-          unless cron_different?
+          # Only compare the crontab if the current resource has a set command.
+          # This may not be set in cases where the Chef comment exists but the
+          # crontab command was commented out.
+          if current_resource.property_is_set?(:command) && !cron_different?
             logger.debug("#{new_resource}: Skipping existing cron entry")
             return
           end
diff --git a/spec/unit/provider/cron_spec.rb b/spec/unit/provider/cron_spec.rb
index 9a276bfffd..3e56dbc8b1 100644
--- a/spec/unit/provider/cron_spec.rb
+++ b/spec/unit/provider/cron_spec.rb
@@ -392,6 +392,27 @@ describe Chef::Provider::Cron do
         expect(cron.command).to eq("/bin/true")
       end
     end
+
+    context "with a matching entry with a commented crontab line" do
+      it "should set cron_exists" do
+        allow(@provider).to receive(:read_crontab).and_return(<<~CRONTAB)
+          0 2 * * * /some/other/command
+
+          # Chef Name: cronhole some stuff
+          #* * * * * /bin/true
+        CRONTAB
+        cron = @provider.load_current_resource
+        expect(@provider.cron_exists).to eq(true)
+        expect(@provider.cron_empty).to eq(false)
+        expect(cron.minute).to eq("*")
+        expect(cron.hour).to eq("*")
+        expect(cron.day).to eq("*")
+        expect(cron.month).to eq("*")
+        expect(cron.weekday).to eq("*")
+        expect(cron.time).to eq(nil)
+        expect(cron.property_is_set?(:command)).to eq(false)
+      end
+    end
   end
 
   describe "cron_different?" do
@@ -691,6 +712,30 @@ describe Chef::Provider::Cron do
       end
     end
 
+    context "when there is a crontab with a matching section with a commented crontab line in it" do
+      before :each do
+        @provider.cron_exists = true
+      end
+
+      it "should add the crontab to the entry" do
+        allow(@provider).to receive(:read_crontab).and_return(<<~CRONTAB)
+          0 2 * * * /some/other/command
+
+          # Chef Name: cronhole some stuff
+          # * * * * * /bin/true
+        CRONTAB
+        expect(@provider).to receive(:write_crontab).with(<<~ENDCRON)
+          0 2 * * * /some/other/command
+
+          # Chef Name: cronhole some stuff
+          * * * * * /bin/true
+          # * * * * * /bin/true
+        ENDCRON
+        @new_resource.minute "*"
+        @provider.run_action(:create)
+      end
+    end
+
     context "when there is a crontab with a matching and identical section" do
       context "when environment variable is not used" do
         before :each do