Implement basic condition DSL framework for tests:

Instead of interrupting task evaluation when condition is not met,
allow the whole task to be evaluated (including condition and
evaluation) so that the interpreter will get all tasks actions (whether
condition is met or not) and be able to query the condition.

* Modify Interpreter#process_task: test if task condition is met before
  applying the actions;
* Implement condition handling in Task and Task::DSL;
* Implement Condition and Condition::DSL (useless as they are, but
  needed to implement later test keywords as part of the condition DSL.

features/tasks/condition.feature

@@ -1,13 +1,12 @@
 Feature: `condition' task keyword
 
-  Scenario: prevents task evaluation when condition is not met
+  Scenario: prevents task actions application when condition is not met
     Given a recipe with:
       """
       task :hello do
         condition { false }
 
-        puts 'evaluated'
-        exit 70
+        echo 'evaluated'
       end
       """
     When I execute the recipe

lib/producer/core.rb

@@ -2,6 +2,8 @@ require 'producer/core/action'
 require 'producer/core/actions/echo'
 require 'producer/core/actions/shell_command'
 require 'producer/core/cli'
+require 'producer/core/condition'
+require 'producer/core/condition/dsl'
 require 'producer/core/env'
 require 'producer/core/errors'
 require 'producer/core/interpreter'

lib/producer/core/condition.rb

@@ -0,0 +1,19 @@
+module Producer
+  module Core
+    class Condition
+      class << self
+        def evaluate(env, &block)
+          DSL.evaluate(env, &block)
+        end
+      end
+
+      def initialize(expression)
+        @expression = expression
+      end
+
+      def !
+        !@expression
+      end
+    end
+  end
+end

lib/producer/core/condition/dsl.rb

@@ -0,0 +1,22 @@
+module Producer
+  module Core
+    class Condition
+      class DSL
+        class << self
+          def evaluate(env, &block)
+            dsl = new(&block)
+            Condition.new(dsl.evaluate)
+          end
+        end
+
+        def initialize(&block)
+          @block = block
+        end
+
+        def evaluate
+          @block.call
+        end
+      end
+    end
+  end
+end

lib/producer/core/interpreter.rb

@@ -6,7 +6,7 @@ module Producer
       end
 
       def process_task(task)
-        task.actions.each(&:apply)
+        task.actions.each(&:apply) if task.condition_met?
       end
     end
   end

lib/producer/core/task.rb

@@ -1,15 +1,20 @@
 module Producer
   module Core
     class Task
-      attr_reader :name, :actions
+      attr_reader :name, :actions, :condition
 
       def self.evaluate(name, env, &block)
         DSL.evaluate(name, env, &block)
       end
 
-      def initialize(name, actions = [])
-        @name     = name
-        @actions  = actions
+      def initialize(name, actions = [], condition = true)
+        @name       = name
+        @actions    = actions
+        @condition  = condition
+      end
+
+      def condition_met?
+        !!@condition
       end
     end
   end

lib/producer/core/task/dsl.rb

@@ -6,7 +6,7 @@ module Producer
           def evaluate(name, env, &block)
             dsl = new(&block)
             dsl.evaluate(env)
-            Task.new(name, dsl.actions)
+            Task.new(name, dsl.actions, dsl.condition)
           end
 
           def define_action(keyword, klass)
@@ -22,20 +22,19 @@ module Producer
         attr_accessor :actions
 
         def initialize(&block)
-          @block    = block
-          @actions  = []
+          @block      = block
+          @actions    = []
+          @condition  = true
         end
 
         def evaluate(env)
           @env = env
           instance_eval &@block
-        rescue ConditionNotMetError
         end
 
-        private
-
         def condition(&block)
-          fail ConditionNotMetError unless block.call
+          @condition = Condition.evaluate(@env, &block) if block
+          @condition
         end
       end
     end

spec/producer/core/condition/dsl_spec.rb

@@ -0,0 +1,47 @@
+require 'spec_helper'
+
+module Producer::Core
+  describe Condition::DSL do
+    let(:block)   { proc { :some_condition_code } }
+    let(:env)     { double('env') }
+    subject(:dsl) { Condition::DSL.new(&block) }
+
+    describe '.evaluate' do
+      it 'builds a new DSL sandbox with given code' do
+        expect(Condition::DSL).to receive(:new).with(&block).and_call_original
+        Condition::DSL.evaluate(env, &block)
+      end
+
+      it 'evaluates the DSL sandbox code' do
+        dsl = double('dsl')
+        allow(Condition::DSL).to receive(:new) { dsl }
+        expect(dsl).to receive(:evaluate)
+        Condition::DSL.evaluate(env, &block)
+      end
+
+      it 'builds a condition with value returned from DSL evaluation' do
+        expect(Condition)
+          .to receive(:new).with(dsl.evaluate)
+        Condition::DSL.evaluate(env, &block)
+      end
+
+      it 'returns the condition' do
+        condition = double('task')
+        allow(Condition).to receive(:new) { condition }
+        expect(Condition::DSL.evaluate(env, &block)).to be condition
+      end
+    end
+
+    describe '#initialize' do
+      it 'assigns the code' do
+        expect(dsl.instance_eval { @block }).to be block
+      end
+    end
+
+    describe '#evaluate' do
+      it 'returns the value returned by the assigned block' do
+        expect(dsl.evaluate).to eq block.call
+      end
+    end
+  end
+end

spec/producer/core/condition_spec.rb

@@ -0,0 +1,39 @@
+require 'spec_helper'
+
+module Producer::Core
+  describe Condition do
+    let(:expression)  { double('expression') }
+    let(:condition)   { Condition.new(expression) }
+
+    describe '.evaluate' do
+      let(:env)   { double('env') }
+      let(:block) { proc { :some_condition_code } }
+
+      it 'delegates to DSL.evaluate' do
+        expect(Condition::DSL)
+          .to receive(:evaluate).with(env) do |&b|
+            expect(b.call).to eq :some_condition_code
+          end
+        Condition.evaluate(env, &block)
+      end
+
+      it 'returns the evaluated condition' do
+        condition = double('condition')
+        allow(Condition::DSL).to receive(:evaluate) { condition }
+        expect(Condition.evaluate(env, &block)).to be condition
+      end
+    end
+
+    describe '#initialize' do
+      it 'assigns the expression' do
+        expect(condition.instance_eval { @expression }).to be expression
+      end
+    end
+
+    describe '#!' do
+      it 'returns the negated expression' do
+        expect(condition.!).to be !expression
+      end
+    end
+  end
+end

spec/producer/core/interpreter_spec.rb

@@ -12,12 +12,29 @@ module Producer::Core
     end
 
     describe '#process_task' do
-      it 'applies the task actions' do
-        action = double('action')
-        task = double('task')
+      let(:action)  { double('action') }
+      let(:task)    { double('task').as_null_object }
+
+      before do
         allow(task).to receive(:actions) { [action] }
-        expect(action).to receive(:apply)
-        interpreter.process_task(task)
+      end
+
+      context 'when task condition is met' do
+        it 'applies the actions' do
+          expect(action).to receive(:apply)
+          interpreter.process_task(task)
+        end
+      end
+
+      context 'when task condition is not met' do
+        before do
+          allow(task).to receive(:condition_met?) { false }
+        end
+
+        it 'does not apply the actions' do
+          expect(action).not_to receive(:apply)
+          interpreter.process_task(task)
+        end
       end
     end
   end

spec/producer/core/task/dsl_spec.rb

@@ -27,11 +27,13 @@ module Producer::Core
         Task::DSL.evaluate(name, env, &block)
       end
 
-      it 'builds a task with its name and registered actions' do
+      it 'builds a task with its name, actions and condition' do
         dsl = double('dsl').as_null_object
         allow(Task::DSL).to receive(:new) { dsl }
-        allow(dsl).to receive(:actions) { [:some_action]}
-        expect(Task).to receive(:new).with(:some_task, [:some_action])
+        allow(dsl).to receive(:actions) { [:some_action] }
+        allow(dsl).to receive(:condition) { :some_condition }
+        expect(Task)
+          .to receive(:new).with(:some_task, [:some_action], :some_condition)
         Task::DSL.evaluate(name, env, &block)
       end
 
@@ -53,6 +55,10 @@ module Producer::Core
       it 'assigns no action' do
         expect(dsl.actions).to be_empty
       end
+
+      it 'assigns true as the condition' do
+        expect(dsl.instance_eval { @condition }).to be_true
+      end
     end
 
     describe '#actions' do
@@ -89,27 +95,35 @@ module Producer::Core
       end
     end
 
-    describe '#condition' do
-      context 'when met (block evals to true)' do
-        let(:block) { proc {
-          condition { true }
-          throw :after_condition
-        } }
+    context 'DSL specific methods' do
+      subject(:dsl) { Task::DSL.new(&block).evaluate(env) }
 
-        it 'evaluates all the block' do
-          expect { dsl.evaluate(env) }
-            .to throw_symbol :after_condition
+      describe '#condition' do
+        context 'when a block is given' do
+          let(:block) { proc { condition { :some_value } } }
+
+          it 'builds a new evaluated condition' do
+            expect(Condition)
+              .to receive(:evaluate).with(env) do |&b|
+                expect(b.call).to eq :some_value
+              end
+            dsl
+          end
+
+          it 'assigns the new condition' do
+            condition = double('condition').as_null_object
+            allow(Condition).to receive(:evaluate) { condition }
+            expect(dsl.condition).to be condition
+          end
         end
       end
+    end
 
-      context 'when not met (block evals to false)' do
-        let(:block) { proc {
-          condition { false }
-          throw :after_condition
-        } }
-
-        it 'stops block evaluation' do
-          expect { dsl.evaluate(env) }.not_to throw_symbol :after_condition
+    describe '#condition' do
+      context 'without block' do
+        it 'returns the assigned condition' do
+          dsl.instance_eval { @condition = :some_condition }
+          expect(dsl.condition).to be :some_condition
         end
       end
     end

spec/producer/core/task_spec.rb

@@ -4,7 +4,8 @@ module Producer::Core
   describe Task do
     let(:name)      { :some_task }
     let(:action)    { double('action') }
-    subject(:task)  { Task.new(name, [action]) }
+    let(:condition) { double('condition') }
+    subject(:task)  { Task.new(name, [action], condition) }
 
     describe '.evaluate' do
       let(:env)   { double('env') }
@@ -34,12 +35,20 @@ module Producer::Core
         expect(task.instance_eval { @actions }).to eq [action]
       end
 
+      it 'assigns the condition' do
+        expect(task.instance_eval { @condition }).to eq condition
+      end
+
       context 'when only the name is given as argument' do
         subject(:task)  { Task.new(name) }
 
         it 'assigns no action' do
           expect(task.actions).to be_empty
         end
+
+        it 'assigns a truthy condition' do
+          expect(task.condition).to be_true
+        end
       end
     end
 
@@ -54,5 +63,29 @@ module Producer::Core
         expect(task.actions).to eq [action]
       end
     end
+
+    describe '#condition' do
+      it 'returns the assigned condition' do
+        expect(task.condition).to be condition
+      end
+    end
+
+    describe '#condition_met?' do
+      context 'when condition is truthy' do
+        let(:condition) { Condition.new(true) }
+
+        it 'returns true' do
+          expect(task.condition_met?).to be true
+        end
+      end
+
+      context 'when condition is falsy' do
+        let(:condition) { Condition.new(false) }
+
+        it 'returns false' do
+          expect(task.condition_met?).to be false
+        end
+      end
+    end
   end
 end