1 files changed, 122 insertions, 0 deletions
diff --git a/lib/chef/resource/file/verification.rb b/lib/chef/resource/file/verification.rb
new file mode 100644
index 0000000000..f1ca0f1883
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+++ b/lib/chef/resource/file/verification.rb
@@ -0,0 +1,122 @@
+#
+# Author:: Steven Danna (<steve@chef.io>)
+# Copyright:: Copyright (c) 2014 Chef Software, Inc
+# License:: Apache License, Version 2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+require 'chef/exceptions'
+require 'chef/guard_interpreter'
+require 'chef/mixin/descendants_tracker'
+
+class Chef
+  class Resource
+    class File < Chef::Resource
+
+      #
+      # See RFC 027 for a full specification
+      #
+      # File verifications allow user-supplied commands a means of
+      # preventing file reosurce content deploys.  Their intended use
+      # is to verify the contents of a temporary file before it is
+      # deployed onto the system.
+      #
+      # Similar to not_if and only_if, file verifications can take a
+      # ruby block, which will be called, or a string, which will be
+      # executed as a Shell command.
+      #
+      # Additonally, Chef or third-party verifications can ship
+      # "registered verifications" that the user can use by specifying
+      # a :symbol as the command name.
+      #
+      # To create a registered verification, create a class that
+      # inherits from Chef::Resource::File::Verification and use the
+      # provides class method to give it name.  Registered
+      # verifications are expected to supply a verify instance method
+      # that takes 2 arguments.
+      #
+      # Example:
+      # class Chef
+      #  class Resource
+      #    class File::Verification::Foo < Chef::Resource::File::Verification
+      #      provides :noop
+      #      def verify(path, opts)
+      #        #yolo
+      #        true
+      #      end
+      #    end
+      #  end
+      # end
+      #
+      #
+
+      class Verification
+        extend Chef::Mixin::DescendantsTracker
+
+        def self.provides(name)
+          @provides = name
+        end
+
+        def self.provides?(name)
+          @provides == name
+        end
+
+        def self.lookup(name)
+          c = descendants.find {|d| d.provides?(name) }
+          if c.nil?
+            raise Chef::Exceptions::VerificationNotFound.new "No file verification for #{name} found."
+          end
+          c
+        end
+
+        def initialize(parent_resource, command, opts, &block)
+          @command, @command_opts = command, opts
+          @block = block
+          @parent_resource = parent_resource
+        end
+
+        def verify(path, opts={})
+          Chef::Log.debug("Running verification[#{self}] on #{path}")
+          if @block
+            verify_block(path, opts)
+          elsif @command.is_a?(Symbol)
+            verify_registered_verification(path, opts)
+          elsif @command.is_a?(String)
+            verify_command(path, opts)
+          end
+        end
+
+        # opts is currently unused, but included in the API
+        # to support future extensions
+        def verify_block(path, opts)
+          @block.call(path)
+        end
+
+        # We reuse Chef::GuardInterpreter in order to support
+        # the same set of options that the not_if/only_if blocks do
+        def verify_command(path, opts)
+          command = @command % {:file => path}
+          interpreter = Chef::GuardInterpreter.for_resource(@parent_resource, command, @command_opts)
+          interpreter.evaluate
+        end
+
+        def verify_registered_verification(path, opts)
+          verification_class = Chef::Resource::File::Verification.lookup(@command)
+          v = verification_class.new(@parent_resource, @command, @command_opts, &@block)
+          v.verify(path, opts)
+        end
+      end
+    end
+  end
+end