Fixing #448 - relationships have their own syntax

You can now specify relationships directly in the language:

  File[/foo] -> Service[bar]

Specifies a normal dependency while:

  File[/foo] ~> Service[bar]

Specifies a subscription.

You can also do relationship chaining, specifying multiple
relationships on a single line:

  File[/foo] -> Package[baz] -> Service[bar]

Note that while it's confusing, you don't have to have all
of the arrows be the same direction:

  File[/foo] -> Service[bar] <~ Package[baz]

This can provide some succinctness at the cost of readability.

You can also specify full resources, rather than just
resource refs:

    file { "/foo": ensure => present } -> package { bar: ensure => installed }

But wait! There's more!  You can also specify a subscription on either side
of the relationship marker:

    yumrepo { foo: .... }
    package { bar: provider => yum, ... }
    Yumrepo <| |> -> Package <| provider == yum |>

This, finally, provides easy many to many relationships in Puppet, but it also opens
the door to massive dependency cycles.  This last feature is a very powerful stick,
and you can considerably hurt yourself with it.

Signed-off-by: Luke Kanies <luke@puppetlabs.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/lib/puppet/parser/compiler.rb b/lib/puppet/parser/compiler.rb
index 8e84f5a5b..fd7d9680b 100644
--- a/lib/puppet/parser/compiler.rb
+++ b/lib/puppet/parser/compiler.rb
@@ -21,13 +21,17 @@ class Puppet::Parser::Compiler
         raise Puppet::Error, "#{detail} on node #{node.name}"
     end
 
-    attr_reader :node, :facts, :collections, :catalog, :node_scope, :resources
+    attr_reader :node, :facts, :collections, :catalog, :node_scope, :resources, :relationships
 
     # Add a collection to the global list.
     def add_collection(coll)
         @collections << coll
     end
 
+    def add_relationship(dep)
+        @relationships << dep
+    end
+
     # Store a resource override.
     def add_override(override)
         # If possible, merge the override in immediately.
@@ -144,6 +148,10 @@ class Puppet::Parser::Compiler
         found
     end
 
+    def evaluate_relationships
+        @relationships.each { |rel| rel.evaluate(catalog) }
+    end
+
     # Return a resource by either its ref or its type and title.
     def findresource(*args)
         @catalog.resource(*args)
@@ -337,6 +345,8 @@ class Puppet::Parser::Compiler
     # Make sure all of our resources and such have done any last work
     # necessary.
     def finish
+        evaluate_relationships()
+
         resources.each do |resource|
             # Add in any resource overrides.
             if overrides = resource_overrides(resource)
@@ -374,6 +384,9 @@ class Puppet::Parser::Compiler
         # but they each refer back to the scope that created them.
         @collections = []
 
+        # The list of relationships to evaluate.
+        @relationships = []
+
         # For maintaining the relationship between scopes and their resources.
         @catalog = Puppet::Resource::Catalog.new(@node.name)
         @catalog.version = known_resource_types.version