Implement multistep

lib/vagrant/action.rb

@@ -56,6 +56,7 @@ module Vagrant
   #
   class Action
     autoload :Environment, 'vagrant/action/environment'
+    autoload :MultiStep,   'vagrant/action/multistep'
     autoload :Step,        'vagrant/action/step'
     autoload :Warden,      'vagrant/action/warden'
 

lib/vagrant/action/multistep.rb

@@ -0,0 +1,51 @@
+module Vagrant
+  class Action
+    class MultiStep < Step
+      def initialize
+        @steps = []
+      end
+
+      def step(step_class, *extra_inputs)
+        # Get the options hash and set the defaults
+        options = {}
+        options = extra_inputs.pop if extra_inputs.last.kind_of?(Hash)
+
+        # Append the step
+        @steps << [step_class, extra_inputs, options]
+      end
+
+      def call(params=nil)
+        params ||= {}
+
+        # Instantiate all the steps
+        instances = @steps.map { |s, inputs, options| [s.new, inputs, options] }
+
+        # For each step, call it with proper inputs, using the output
+        # of that call as inputs to the next.
+        instances.inject(params) do |inputs, data|
+          step, extra_inputs, options = data
+
+          # If there are extra inputs for this step, add them to the
+          # parameters based on the initial parameters.
+          extra_inputs.each do |extra_input|
+            inputs[extra_input] = params[extra_input]
+          end
+
+          # If we have inputs to remap, remap them.
+          if options[:map]
+            options[:map].each do |from, to|
+              # This sets the input to the new key while removing the
+              # the old key from the same hash. Kind of sneaky, but
+              # hopefully this comment makes it clear.
+              inputs[to] = inputs.delete(from)
+            end
+          end
+
+          # Call the actual step, using the results for the next
+          # iteration.
+          step.call(inputs)
+        end
+      end
+    end
+  end
+end

lib/vagrant/action/step.rb

@@ -33,9 +33,15 @@ module Vagrant
 
       # Validates that the output matches the specification provided, and
       # raises a RuntimeError if it does not.
-      def self.validate_output(value)
+      def self.process_output(value)
+        # The return value must be a Hash, so we just coerce it to that.
+        value = {} if !value.kind_of?(Hash)
+
+        # Verify that we have all the outputs
         missing = outputs - value.keys
         raise RuntimeError, "Missing output keys: #{missing}" if !missing.empty?
+
+        return value
       end
 
       # This calls the step with the given parameters, and returns a hash
@@ -49,7 +55,7 @@ module Vagrant
       # @option options [Boolean] :validate_output Whether to validate the
       #   output or not.
       # @return [Hash] Output
-      def call(params, options=nil)
+      def call(params={}, options=nil)
         options = {
           :method => :execute,
           :validate_output => true
@@ -61,8 +67,9 @@ module Vagrant
         # Call the actual implementation
         results = send(options[:method])
 
-        # Validate the outputs
-        self.class.validate_output(results) if options[:validate_output]
+        # Validate the outputs if it is enabled and the list of configured
+        # outputs is not empty.
+        results = self.class.process_output(results) if options[:validate_output]
 
         # Return the final results
         results

test/unit/vagrant/action/multistep_test.rb

@@ -0,0 +1,82 @@
+require File.expand_path("../../../base", __FILE__)
+
+describe Vagrant::Action::MultiStep do
+  it "should compose a series of steps" do
+    step_A = Class.new(Vagrant::Action::Step) do
+      input  :obj
+      output :obj
+
+      def execute
+        @obj << "A"
+        return :obj => @obj
+      end
+    end
+
+    step_B = Class.new(Vagrant::Action::Step) do
+      input  :obj
+      output :result
+
+      def execute
+        return :result => (@obj << "B")
+      end
+    end
+
+    obj = []
+
+    ms = described_class.new
+    ms.step step_A
+    ms.step step_B
+    ms.call(:obj => obj).should == { :result => ["A", "B"] }
+  end
+
+  it "should allow for custom inputs to pass to specific steps" do
+    step_A = Class.new(Vagrant::Action::Step) do
+      def execute
+        # Do nothing.
+      end
+    end
+
+    step_B = Class.new(Vagrant::Action::Step) do
+      input :obj
+
+      def execute
+        @obj << "B"
+      end
+    end
+
+    obj = []
+
+    ms = described_class.new
+    ms.step step_A
+    ms.step step_B, :obj
+    ms.call(:obj => obj)
+
+    obj.should == ["B"]
+  end
+
+  it "should be able to remap input names" do
+    step_A = Class.new(Vagrant::Action::Step) do
+      output :foo
+
+      def execute
+        return :foo => "A"
+      end
+    end
+
+    step_B = Class.new(Vagrant::Action::Step) do
+      input  :from
+      output :value
+
+      def execute
+        return :value => @from
+      end
+    end
+
+    obj = []
+
+    ms = described_class.new
+    ms.step step_A
+    ms.step step_B, :map => { :foo => :from }
+    ms.call.should == { :value => "A" }
+  end
+end

test/unit/vagrant/action/step_test.rb

@@ -18,7 +18,7 @@ describe Vagrant::Action::Step do
       input :foo
     end
 
-    expect { step_class.new.call({}) }.to raise_error(ArgumentError)
+    expect { step_class.new.call }.to raise_error(ArgumentError)
   end
 
   it "calls a custom method if given" do
@@ -31,27 +31,39 @@ describe Vagrant::Action::Step do
     step_class.new.call({}, :method => :prepare).should == { :foo => 12 }
   end
 
-  it "raises an exception if missing outputs" do
-    step_class = Class.new(described_class) do
-      output :foo
-
-      def execute
-        return :bar => 12
+  describe "outputs" do
+    it "return an empty hash if no outputs are specified" do
+      step_class = Class.new(described_class) do
+        def execute
+          return 12
+        end
       end
+
+      step_class.new.call.should == {}
     end
 
-    expect { step_class.new.call({}) }.to raise_error(RuntimeError)
-  end
+    it "raises an exception if missing outputs" do
+      step_class = Class.new(described_class) do
+        output :foo
 
-  it "does nothing if missing outputs but we disabled validating" do
-    step_class = Class.new(described_class) do
-      output :foo
-
-      def execute
-        return :bar => 12
+        def execute
+          return :bar => 12
+        end
       end
+
+      expect { step_class.new.call }.to raise_error(RuntimeError)
     end
 
-    step_class.new.call({}, :validate_output => false).should == { :bar => 12 }
+    it "does nothing if missing outputs but we disabled validating" do
+      step_class = Class.new(described_class) do
+        output :foo
+
+        def execute
+          return :bar => 12
+        end
+      end
+
+      step_class.new.call({}, :validate_output => false).should == { :bar => 12 }
+    end
   end
 end