Improve source recipe keyword feature:

* Improve error reporting from sourced recipe;
* Extract cucumber feature from recipe one.

features/recipe.feature

@@ -23,16 +23,3 @@ Feature: recipe evaluation
       \AOK
       recipe.rb:3:.+invalid recipe keyword `invalid_keyword'
       """
-
-  Scenario: source keyword, requires a recipe file
-    Given a recipe with:
-      """
-      source 'sourced_recipe'
-      """
-    And a file named "sourced_recipe.rb" with:
-      """
-      puts 'sourced recipe'
-      """
-    When I execute the recipe
-    Then the exit status must be 0
-    And the output must contain "sourced recipe"

features/source.feature

@@ -0,0 +1,33 @@
+Feature: source recipe keyword
+
+  Scenario: requires a recipe file
+    Given a recipe with:
+      """
+      source 'sourced_recipe'
+      """
+    And a file named "sourced_recipe.rb" with:
+      """
+      puts 'sourced recipe'
+      """
+    When I execute the recipe
+    Then the exit status must be 0
+    And the output must contain "sourced recipe"
+
+  Scenario: reports errors from sourced recipes
+    Given a recipe with:
+      """
+      source 'sourced_recipe'
+      """
+    And a file named "sourced_recipe.rb" with:
+      """
+      puts 'OK'
+
+      invalid_keyword
+      """
+    When I execute the recipe
+    Then the output must match:
+      """
+      \AOK
+      sourced_recipe.rb:3:.+invalid recipe keyword `invalid_keyword'
+      recipe.rb:1:.+
+      """

lib/producer/core/recipe/dsl.rb

@@ -27,7 +27,7 @@ module Producer
         private
 
         def source(filepath)
-          instance_eval File.read("./#{filepath}.rb")
+          instance_eval File.read("./#{filepath}.rb"), "#{filepath}.rb"
         end
 
         def task(name, &block)

spec/producer/core/recipe/dsl_spec.rb

@@ -59,12 +59,21 @@ module Producer::Core
       subject(:dsl) { Recipe::DSL.new(&code).evaluate(env) }
 
       describe '#source' do
-        let(:code)    { "source '#{fixture_path_for 'recipes/error'}'" }
-        subject(:dsl) { Recipe::DSL.new code }
+        let(:filepath)  { fixture_path_for 'recipes/error' }
+        let(:code)      { "source '#{filepath}'" }
+        subject(:dsl)   { Recipe::DSL.new code }
 
         it 'sources the recipe given as argument' do
           expect { dsl.evaluate(env) }.to raise_error(RuntimeError, 'error from recipe')
         end
+
+        context 'invalid sourced recipe' do
+          it 'reports the sourced recipe file path in the error' do
+            expect { dsl.evaluate(env) }.to raise_error(RuntimeError) { |e|
+              expect(e.backtrace.first).to match /\A#{filepath}/
+            }
+          end
+        end
       end
 
       describe '#tasks' do