Fix neutron subnets with empty values.

Subnet was expended with ability to set and update parameters like
specifing dns servers, allocation pools and also specific host routes.
Sadly it introduced issue when calling neutron_subnet without specifying
values for these parameters.
Closes-Bug: #1312628

Change-Id: Id1207ab793fc65c43c10afcfe2271e2c02a912d3

lib/puppet/provider/neutron_subnet/neutron.rb

@@ -50,6 +50,7 @@ def self.prefetch(resources)
 
   def self.parse_allocation_pool(values)
     allocation_pools = []
+    return [] if values.empty?
     for value in Array(values)
       matchdata = /\{\s*"start"\s*:\s*"(.*)"\s*,\s*"end"\s*:\s*"(.*)"\s*\}/.match(value)
       start_ip = matchdata[1]
@@ -61,6 +62,7 @@ def self.parse_allocation_pool(values)
 
   def self.parse_host_routes(values)
     host_routes = []
+    return [] if values.empty?
     for value in Array(values)
       matchdata = /\{\s*"destination"\s*:\s*"(.*)"\s*,\s*"nexthop"\s*:\s*"(.*)"\s*\}/.match(value)
       destination = matchdata[1]
@@ -164,19 +166,23 @@ def enable_dhcp=(value)
   end
 
   def dns_nameservers=(values)
-    opts = ["#{name}", "--dns-nameservers", "list=true"]
-    for value in values
-      opts << value
+    unless values.empty?
+      opts = ["#{name}", "--dns-nameservers", "list=true"]
+      for value in values
+        opts << value
+      end
+      auth_neutron('subnet-update', opts)
     end
-    auth_neutron('subnet-update', opts)
   end
 
   def host_routes=(values)
-    opts = ["#{name}", "--host-routes", "type=dict", "list=true"]
-    for value in values
-      opts << value
+    unless values.empty?
+      opts = ["#{name}", "--host-routes", "type=dict", "list=true"]
+      for value in values
+        opts << value
+      end
+      auth_neutron('subnet-update', opts)
     end
-    auth_neutron('subnet-update', opts)
   end
 
   [

spec/unit/provider/neutron_subnet/neutron_spec.rb

@@ -67,6 +67,14 @@
                                             'destination=12.0.0.0/24,nexthop=10.0.0.2'])
       provider.host_routes=(['destination=12.0.0.0/24,nexthop=10.0.0.2'])
     end
+
+    it 'should not update if dns_nameservers are empty' do
+      provider.dns_nameservers=('')
+    end
+
+    it 'should not update if host_routes are empty' do
+      provider.host_routes=('')
+    end
   end
 
 end