(#5605) Prefetch doesnt work with composite keys

The uniqueness_key method of a type or resource object should return a
key that can be used to identify this resource. In fact puppet seldomly
uses this method and instead uses resource[:name] as an identifier.

While this is totally fine for resourcetypes with a single
key_attribute (and resource[:name] returning the namevar), it breaks
things as soon as one creates a type with a composite key (prefetching
for example is broken). To ease the process of replacing calls to
resource[:name] to resource.uniqueness_key, the method uniqueness_key now
just returns name_var if there is only one key_attribute (immitating
self[:name]) and only returns an array of all the values of all the
key_attributes if we have more than one key_attribute.

The resourcehash which is passed to providers in their prefetch method
is now build with uniqueness_key as the hashkey. Because of the new
behaviour of uniqueness_key we hopefully wont break existing providers
while allowing new providers for types with composite keys to implement
correct prefetch methods.

1 files changed, 7 insertions, 2 deletions

diff --git a/lib/puppet/resource.rb b/lib/puppet/resource.rb
index 4f0d50750..a52796800 100644
--- a/lib/puppet/resource.rb
+++ b/lib/puppet/resource.rb
@@ -237,11 +237,16 @@ class Puppet::Resource
     h = self.to_hash
     h[namevar] ||= h[:name]
     h[:name]   ||= h[namevar]
-    h.values_at(*key_attributes.sort_by { |k| k.to_s })
+    # Simulate the same behaviour like Type#uniqueness_key
+    if key_attributes.size == 1
+      h[namevar]
+    else
+      h.values_at(*key_attributes)
+    end
   end
 
   def key_attributes
-    return(resource_type.respond_to? :key_attributes) ? resource_type.key_attributes : [:name]
+    resource_type.respond_to?(:key_attributes) ? resource_type.key_attributes : [:name]
   end
 
   # Convert our resource to Puppet code.