Allowing formats to specify the methods they require

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

1 files changed, 52 insertions, 15 deletions

diff --git a/lib/puppet/network/format.rb b/lib/puppet/network/format.rb
index db9458ee3..d50141ea9 100644
--- a/lib/puppet/network/format.rb
+++ b/lib/puppet/network/format.rb
@@ -6,11 +6,14 @@ require 'puppet/provider/confiner'
 class Puppet::Network::Format
     include Puppet::Provider::Confiner
 
-    attr_reader :name, :mime, :weight
+    attr_reader :name, :mime, :weight, :required_methods
 
     def initialize(name, options = {}, &block)
         @name = name.to_s.downcase.intern
 
+        # This must be done early the values can be used to set required_methods
+        define_method_names()
+
         if mime = options[:mime]
             self.mime = mime
             options.delete(:mime)
@@ -25,26 +28,28 @@ class Puppet::Network::Format
             @weight = 5
         end
 
+        if methods = options[:required_methods]
+            @required_methods = methods
+            options.delete(:required_methods)
+        else
+            @required_methods = [:intern_method, :intern_multiple_method, :render_multiple_method, :render_method]
+        end
+
         unless options.empty?
             raise ArgumentError, "Unsupported option(s) %s" % options.keys
         end
 
         instance_eval(&block) if block_given?
-
-        @intern_method = "from_%s" % name
-        @render_method = "to_%s" % name
-        @intern_multiple_method = "from_multiple_%s" % name
-        @render_multiple_method = "to_multiple_%s" % name
     end
 
     def intern(klass, text)
         return klass.send(intern_method, text) if klass.respond_to?(intern_method)
-        raise NotImplementedError, "%s can not intern instances from %s" % [klass, mime]
+        raise NotImplementedError, "%s does not respond to %s; can not intern instances from %s" % [klass, intern_method, mime]
     end
 
     def intern_multiple(klass, text)
         return klass.send(intern_multiple_method, text) if klass.respond_to?(intern_multiple_method)
-        raise NotImplementedError, "%s can not intern multiple instances from %s" % [klass, mime]
+        raise NotImplementedError, "%s does not respond to %s; can not intern multiple instances from %s" % [klass, intern_multiple_method, mime]
     end
 
     def mime=(mime)
@@ -53,21 +58,27 @@ class Puppet::Network::Format
 
     def render(instance)
         return instance.send(render_method) if instance.respond_to?(render_method)
-        raise NotImplementedError, "%s can not render instances to %s" % [instance.class, mime]
+        raise NotImplementedError, "%s does not respond to %s; can not render instances to %s" % [instance.class, render_method, mime]
     end
 
     def render_multiple(instances)
         # This method implicitly assumes that all instances are of the same type.
         return instances[0].class.send(render_multiple_method, instances) if instances[0].class.respond_to?(render_multiple_method)
-        raise NotImplementedError, "%s can not intern multiple instances to %s" % [instances[0].class, mime]
+        raise NotImplementedError, "%s does not respond to %s; can not intern multiple instances to %s" % [instances[0].class, render_multiple_method, mime]
+    end
+
+    def required_methods_present?(klass)
+        [:intern_method, :intern_multiple_method, :render_multiple_method].each do |name|
+            return false unless required_method_present?(name, klass, :class)
+        end
+
+        return false unless required_method_present?(:render_method, klass, :instance)
+
+        return true
     end
 
     def supported?(klass)
-        suitable? and
-            klass.respond_to?(intern_method) and
-            klass.respond_to?(intern_multiple_method) and
-            klass.respond_to?(render_multiple_method) and
-            klass.instance_methods.include?(render_method)
+        suitable? and required_methods_present?(klass)
     end
 
     def to_s
@@ -77,4 +88,30 @@ class Puppet::Network::Format
     private
 
     attr_reader :intern_method, :render_method, :intern_multiple_method, :render_multiple_method
+
+    def define_method_names
+        @intern_method = "from_%s" % name
+        @render_method = "to_%s" % name
+        @intern_multiple_method = "from_multiple_%s" % name
+        @render_multiple_method = "to_multiple_%s" % name
+    end
+
+    def required_method_present?(name, klass, type)
+        return true unless required_methods.include?(name)
+
+        method = send(name)
+
+        if type == :class
+            has_method = klass.respond_to?(method)
+            message = "class does not respond to %s" % method
+        else
+            has_method = klass.instance_methods.include?(method)
+            message = "class instances do not respond to %s" % method
+        end
+
+        return true if has_method
+
+        Puppet.debug "Format %s not supported for %s; %s" % [name, klass, message]
+        return false
+    end
 end