WIP

8 files changed, 421 insertions, 28 deletions

diff --git a/lib/chef/decorator.rb b/lib/chef/decorator.rb
new file mode 100644
index 0000000000..aa1f399d9f
--- /dev/null
+++ b/lib/chef/decorator.rb
@@ -0,0 +1,81 @@
+#--
+# Copyright:: Copyright 2016 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 "delegate"
+
+class Chef
+  class Decorator < SimpleDelegator
+    NULL = ::Object.new
+
+    def initialize(obj: NULL)
+      super(obj) unless obj == NULL
+      @__defined_methods__ = []
+    end
+
+    # if we wrap a nil then decorator.nil? should be true
+    def nil?
+      __getobj__.nil?
+    end
+
+    # if we wrap a Hash then decorator.is_a?(Hash) should be true
+    def is_a?(klass)
+      __getobj__.is_a?(klass) || super
+    end
+
+    # if we wrap a Hash then decorator.kind_of?(Hash) should be true
+    def kind_of?(klass)
+      __getobj__.kind_of?(klass) || super
+    end
+
+    # reset our methods on the instance if the object changes under us (this also
+    # clears out the closure over the target we create in method_missing below)
+    def __setobj__(obj)
+      __reset_methods__
+      super
+    end
+
+    # this is the ruby 2.2/2.3 implementation of Delegator#method_missing() with
+    # adding the define_singleton_method call and @__defined_methods__ tracking
+    def method_missing(m, *args, &block)
+      r = true
+      target = self.__getobj__ { r = false }
+
+      if r && target.respond_to?(m)
+        # these next 4 lines are the patched code
+        define_singleton_method(m) do |*args, &block|
+          target.__send__(m, *args, &block)
+        end
+        @__defined_methods__.push(m)
+        target.__send__(m, *args, &block)
+      elsif ::Kernel.respond_to?(m, true)
+        ::Kernel.instance_method(m).bind(self).call(*args, &block)
+      else
+        super(m, *args, &block)
+      end
+    end
+
+    private
+
+    # used by __setobj__ to clear the methods we've built on the instance.
+    def __reset_methods__
+      @__defined_methods__.each do |m|
+        singleton_class.send(:undef_method, m)
+      end
+      @__defined_methods__ = []
+    end
+  end
+end
diff --git a/lib/chef/decorator/lazy.rb b/lib/chef/decorator/lazy.rb
new file mode 100644
index 0000000000..067d6bd7f8
--- /dev/null
+++ b/lib/chef/decorator/lazy.rb
@@ -0,0 +1,50 @@
+#--
+# Copyright:: Copyright 2016 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/decorator"
+
+class Chef
+  class Decorator
+    # Lazy wrapper to delay construction of an object until a method is
+    # called against the object.
+    #
+    # @example
+    #   a = Chef::Decorator::Lazy.new { puts "allocated" }
+    #   puts "start"
+    #   puts a.class
+    #
+    #   outputs:
+    #
+    #   start
+    #   allocated
+    #   String
+    #
+    # @since 12.10.x
+    class Lazy < Decorator
+      def initialize(&block)
+        super
+        @block = block
+      end
+
+      def __getobj__
+        __setobj__(@block.call) unless defined?(@delegate_sd_obj)
+        super
+      end
+
+    end
+  end
+end
diff --git a/lib/chef/decorator/lazy_array.rb b/lib/chef/decorator/lazy_array.rb
new file mode 100644
index 0000000000..3879aea5f6
--- /dev/null
+++ b/lib/chef/decorator/lazy_array.rb
@@ -0,0 +1,44 @@
+#--
+# Copyright:: Copyright 2016 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/decorator"
+
+class Chef
+  class Decorator
+    # Lazy wrapper to delay construction of an object until a method is
+    # called against the object.
+    #
+    # @example
+    #   a = Chef::Decorator::Lazy.new { puts "allocated" }
+    #   puts "start"
+    #   puts a.class
+    #
+    #   outputs:
+    #
+    #   start
+    #   allocated
+    #   String
+    #
+    # @since 12.10.x
+    class LazyArray < Lazy
+      def [](idx)
+        block = @block
+        Lazy.new { block.call[idx] }
+      end
+    end
+  end
+end
diff --git a/lib/chef/provider/package.rb b/lib/chef/provider/package.rb
index 4a37ef533d..ec71832488 100644
--- a/lib/chef/provider/package.rb
+++ b/lib/chef/provider/package.rb
@@ -22,6 +22,8 @@ require "chef/mixin/subclass_directive"
 require "chef/log"
 require "chef/file_cache"
 require "chef/platform"
+require "chef/decorator/lazy"
+require "chef/decorator/lazy_array"
 
 class Chef
   class Provider
@@ -476,32 +478,9 @@ class Chef
 
       # @return [Array] candidate_version(s) as an array
       def candidate_version_array
-        use_multipackage_api? ?
-          [ candidate_version ].flatten :
-          [ LazyObject.new { candidate_version } ]
-      end
-
-      # Wrap single candidate_version in a lazy object to minimize unnecessary API queries.
-      class LazyObject < BasicObject
-        NULL = ::Object.new
-
-        def initialize(&block)
-          @block = block
-          @target = NULL
-        end
-
-        def __obj
-          @target = @block.call if @target == NULL
-          @target
-        end
-
-        def ==(other_object)
-          __obj == other_object
-        end
-
-        def method_missing(method_name, *args, &block)
-          __obj.send(method_name, *args, &block)
-        end
+        # NOTE: even with use_multipackage_api candidate_version may be a bare nil and need wrapping
+        # ( looking at you, dpkg provider... )
+        Chef::Decorator::LazyArray.new { [ candidate_version ].flatten }
       end
 
       # @return [Array] current_version(s) as an array
diff --git a/lib/chef/provider/package/dpkg.rb b/lib/chef/provider/package/dpkg.rb
index a5a80e14d6..e57f58e052 100644
--- a/lib/chef/provider/package/dpkg.rb
+++ b/lib/chef/provider/package/dpkg.rb
@@ -23,9 +23,9 @@ class Chef
   class Provider
     class Package
       class Dpkg < Chef::Provider::Package
-        DPKG_REMOVED = /^Status: deinstall ok config-files/
+        DPKG_REMOVED   = /^Status: deinstall ok config-files/
         DPKG_INSTALLED = /^Status: install ok installed/
-        DPKG_VERSION = /^Version: (.+)$/
+        DPKG_VERSION   = /^Version: (.+)$/
 
         provides :dpkg_package, os: "linux"
 
diff --git a/spec/unit/decorator/lazy_array_spec.rb b/spec/unit/decorator/lazy_array_spec.rb
new file mode 100644
index 0000000000..0c5c2eeee0
--- /dev/null
+++ b/spec/unit/decorator/lazy_array_spec.rb
@@ -0,0 +1,58 @@
+#
+# Author:: Lamont Granquist (<lamont@chef.io>)
+# Copyright:: Copyright 2015-2016, 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 "spec_helper"
+
+describe Chef::Decorator::LazyArray do
+  def foo
+    @foo ||= 1
+  end
+
+  def bar
+    @bar ||= 2
+  end
+
+  let(:decorator) do
+    Chef::Decorator::LazyArray.new { [ foo, bar ] }
+  end
+
+  it "behaves like an array" do
+    expect(decorator[0]).to eql(1)
+    expect(decorator[1]).to eql(2)
+  end
+
+  it "accessing the array elements is lazy" do
+    expect(decorator[0].class).to eql(Chef::Decorator::Lazy)
+    expect(decorator[1].class).to eql(Chef::Decorator::Lazy)
+    expect(@foo).to be nil
+    expect(@bar).to be nil
+  end
+
+  it "calling a method on the array element runs the proc (and both elements are autovivified)" do
+    expect(decorator[0].nil?).to be false
+    expect(@foo).to equal(1)
+    expect(@bar).to equal(2)
+  end
+
+  it "if we loop over the elements and do nothing then its not lazy" do
+    # we don't know how many elements there are unless we evaluate the proc
+    decorator.each { |i| }
+    expect(@foo).to equal(1)
+    expect(@bar).to equal(2)
+  end
+end
diff --git a/spec/unit/decorator/lazy_spec.rb b/spec/unit/decorator/lazy_spec.rb
new file mode 100644
index 0000000000..4ea8301b63
--- /dev/null
+++ b/spec/unit/decorator/lazy_spec.rb
@@ -0,0 +1,39 @@
+#
+# Author:: Lamont Granquist (<lamont@chef.io>)
+# Copyright:: Copyright 2015-2016, 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 "spec_helper"
+
+describe Chef::Decorator::Lazy do
+  let(:decorator) do
+    @a = 0
+    Chef::Decorator::Lazy.new { @a = @a + 1 }
+  end
+
+  it "decorates an object" do
+    expect(decorator.even?).to be false
+  end
+
+  it "the proc runs and does work" do
+    expect(decorator).to eql(1)
+  end
+
+  it "creating the decorator does not cause the proc to run" do
+    decorator
+    expect(@a).to eql(0)
+  end
+end
diff --git a/spec/unit/decorator_spec.rb b/spec/unit/decorator_spec.rb
new file mode 100644
index 0000000000..6d73db2cc4
--- /dev/null
+++ b/spec/unit/decorator_spec.rb
@@ -0,0 +1,142 @@
+#
+# Author:: Lamont Granquist (<lamont@chef.io>)
+# Copyright:: Copyright 2015-2016, 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 "spec_helper"
+
+def impersonates_a(klass)
+  it "#is_a?(#{klass}) is true" do
+    expect(decorator.is_a?(klass)).to be true
+  end
+
+  it "#is_a?(Chef::Decorator) is true" do
+    expect(decorator.is_a?(Chef::Decorator)).to be true
+  end
+
+  it "#kind_of?(#{klass}) is true" do
+    expect(decorator.kind_of?(klass)).to be true
+  end
+
+  it "#kind_of?(Chef::Decorator) is true" do
+    expect(decorator.kind_of?(Chef::Decorator)).to be true
+  end
+
+  it "#instance_of?(#{klass}) is false" do
+    expect(decorator.instance_of?(klass)).to be false
+  end
+
+  it "#instance_of?(Chef::Decorator) is true" do
+    expect(decorator.instance_of?(Chef::Decorator)).to be true
+  end
+
+  it "#class is Chef::Decorator" do
+    expect(decorator.class).to eql(Chef::Decorator)
+  end
+end
+
+describe Chef::Decorator do
+  let(:obj) {}
+  let(:decorator) { Chef::Decorator.new(obj) }
+
+  context "when the obj is a string" do
+    let(:obj) { "STRING" }
+
+    impersonates_a(String)
+
+    it "#nil? is false" do
+      expect(decorator.nil?).to be false
+    end
+
+    it "!! is true" do
+      expect(!!decorator).to be true
+    end
+
+    it "dup returns a decorator" do
+      expect(decorator.dup.class).to be Chef::Decorator
+    end
+
+    it "dup dup's the underlying thing" do
+      expect(decorator.dup.__getobj__).not_to equal(decorator.__getobj__)
+    end
+  end
+
+  context "when the obj is a nil" do
+    let(:obj) { nil }
+
+    it "#nil? is true" do
+      expect(decorator.nil?).to be true
+    end
+
+    it "!! is false" do
+      expect(!!decorator).to be false
+    end
+
+    impersonates_a(NilClass)
+  end
+
+  context "when the obj is an empty Hash" do
+    let(:obj) { {} }
+
+    impersonates_a(Hash)
+
+    it "formats it correctly through ffi-yajl and not the JSON gem" do
+      # this relies on a quirk of pretty formatting whitespace between yajl and ruby's JSON
+      expect(FFI_Yajl::Encoder.encode(decorator, pretty: true)).to eql("{\n\n}\n")
+    end
+  end
+
+  context "whent he obj is a Hash with elements" do
+    let(:obj) { { foo: "bar", baz: "qux" } }
+
+    impersonates_a(Hash)
+
+    it "dup is shallow on the Hash" do
+      expect(decorator.dup[:baz]).to equal(decorator[:baz])
+    end
+
+    it "deep mutating the dup'd hash mutates the origin" do
+      decorator.dup[:baz] << "qux"
+      expect(decorator[:baz]).to eql("quxqux")
+    end
+  end
+
+  context "memoizing methods" do
+    let(:obj) { {} }
+
+    it "calls method_missing only once" do
+      expect(decorator).to receive(:method_missing).once.and_call_original
+      expect(decorator.keys).to eql([])
+      expect(decorator.keys).to eql([])
+    end
+
+    it "switching a Hash to an Array responds to keys then does not" do
+      expect(decorator.respond_to?(:keys)).to be true
+      expect(decorator.keys).to eql([])
+      decorator.__setobj__([])
+      expect(decorator.respond_to?(:keys)).to be false
+      expect { decorator.keys }.to raise_error(NoMethodError)
+    end
+
+    it "memoization of methods happens on the instances, not the classes" do
+      decorator2 = Chef::Decorator.new([])
+      expect(decorator.respond_to?(:keys)).to be true
+      expect(decorator.keys).to eql([])
+      expect(decorator2.respond_to?(:keys)).to be false
+      expect { decorator2.keys }.to raise_error(NoMethodError)
+    end
+  end
+end