Specs for Enumerator::Lazy propagating source yield arity through stages

A lazy stage that passes its source values through unchanged keeps the arity
they were yielded with, so a block belonging to a later stage still receives
them the way a block on the first stage would. In CRuby this is the
LAZY_MEMO_PACKED bit traveling along the chain; stages that replace the value
with a block result clear it.

Covers take, drop, select, reject, take_while, drop_while and grep, plus the
zero-argument yield (which becomes a single nil).

Also adds the existing :enumerable_value_packing examples to grep, the one
Lazy method they did not already cover.

Author: sampokuokkanen

core/enumerator/lazy/drop_spec.rb

@@ -3,6 +3,7 @@
 require_relative '../../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative '../../enumerable/shared/value_packing'
+require_relative 'shared/packed_propagation'
 
 describe "Enumerator::Lazy#drop" do
   describe "value packing of source yields (matches Enumerable#drop)" do
@@ -72,3 +73,12 @@
       s.first(200).drop(100)
   end
 end
+
+describe "Enumerator::Lazy#drop" do
+  describe "propagating the source yield arity to a later stage" do
+    before :each do
+      @stage = -> e { e.drop(0) }
+    end
+    it_behaves_like :enumerator_lazy_packed_propagation, nil
+  end
+end

core/enumerator/lazy/drop_while_spec.rb

@@ -3,6 +3,7 @@
 require_relative '../../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative '../../enumerable/shared/value_packing'
+require_relative 'shared/packed_propagation'
 
 describe "Enumerator::Lazy#drop_while" do
   describe "value packing of source yields (matches Enumerable#drop_while)" do
@@ -80,3 +81,12 @@
       s.first(200).drop_while { |n| n < 100 }
   end
 end
+
+describe "Enumerator::Lazy#drop_while" do
+  describe "propagating the source yield arity to a later stage" do
+    before :each do
+      @stage = -> e { e.drop_while { false } }
+    end
+    it_behaves_like :enumerator_lazy_packed_propagation, nil
+  end
+end

core/enumerator/lazy/grep_spec.rb

@@ -2,8 +2,17 @@
 
 require_relative '../../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative '../../enumerable/shared/value_packing'
+require_relative 'shared/packed_propagation'
 
 describe "Enumerator::Lazy#grep" do
+  describe "value packing of source yields (matches Enumerable#grep)" do
+    before :each do
+      @take = -> e { e.lazy.grep(Object) }
+    end
+    it_behaves_like :enumerable_value_packing, nil
+  end
+
   before :each do
     @yieldsmixed = EnumeratorLazySpecs::YieldsMixed.new.to_enum.lazy
     @eventsmixed = EnumeratorLazySpecs::EventsMixed.new.to_enum.lazy
@@ -119,3 +128,12 @@
       s.first(100).grep(Numeric)
   end
 end
+
+describe "Enumerator::Lazy#grep" do
+  describe "propagating the source yield arity to a later stage" do
+    before :each do
+      @stage = -> e { e.grep(Object) }
+    end
+    it_behaves_like :enumerator_lazy_packed_propagation, nil
+  end
+end

core/enumerator/lazy/reject_spec.rb

@@ -3,6 +3,7 @@
 require_relative '../../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative '../../enumerable/shared/value_packing'
+require_relative 'shared/packed_propagation'
 
 describe "Enumerator::Lazy#reject" do
   describe "value packing of source yields (matches Enumerable#reject)" do
@@ -84,3 +85,12 @@
       s.first(100).reject { |n| false }
   end
 end
+
+describe "Enumerator::Lazy#reject" do
+  describe "propagating the source yield arity to a later stage" do
+    before :each do
+      @stage = -> e { e.reject { false } }
+    end
+    it_behaves_like :enumerator_lazy_packed_propagation, nil
+  end
+end

core/enumerator/lazy/select_spec.rb

@@ -1,6 +1,7 @@
 require_relative '../../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative '../../enumerable/shared/value_packing'
+require_relative 'shared/packed_propagation'
 
 describe "Enumerator::Lazy#select" do
   describe "value packing of source yields (matches Enumerable#select)" do
@@ -109,3 +110,12 @@
     eval_count.should == 1
   end
 end
+
+describe "Enumerator::Lazy#select" do
+  describe "propagating the source yield arity to a later stage" do
+    before :each do
+      @stage = -> e { e.select { true } }
+    end
+    it_behaves_like :enumerator_lazy_packed_propagation, nil
+  end
+end

core/enumerator/lazy/shared/packed_propagation.rb

@@ -0,0 +1,32 @@
+# The propagation checked here is the LAZY_MEMO_PACKED bit traveling along the chain in CRuby.
+describe :enumerator_lazy_packed_propagation, shared: true do
+  # @stage: a Proc wrapping a lazy enumerator in the stage under test, e.g. -> e { e.take(12) }.
+
+  before :each do
+    @yieldsmixed = EnumeratorLazySpecs::YieldsMixed.new.to_enum.lazy
+  end
+
+  it "passes a multiple-argument source yield to a later stage's single-argument block as the first value" do
+    yields = []
+    @stage.call(@yieldsmixed).map { |v| yields << v }.force
+    yields.should == EnumeratorLazySpecs::YieldsMixed.initial_yields
+  end
+
+  it "passes every value of a multiple-argument source yield to a later stage's splat block" do
+    args = nil
+    @stage.call(Enumerator.new { |y| y.yield 1, 2 }.lazy).map { |*a| args = a }.force
+    args.should == [1, 2]
+  end
+
+  it "passes a zero-argument source yield on as a single nil" do
+    args = nil
+    @stage.call(Enumerator.new { |y| y.yield }.lazy).map { |*a| args = a }.force
+    args.should == [nil]
+  end
+
+  it "stops propagating once a stage replaces the value" do
+    yields = []
+    @stage.call(Enumerator.new { |y| y.yield 1, 2 }.lazy).map { |x| x }.map { |*a| yields << a }.force
+    yields.should == [[1]]
+  end
+end

core/enumerator/lazy/take_spec.rb

@@ -3,6 +3,7 @@
 require_relative '../../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative '../../enumerable/shared/value_packing'
+require_relative 'shared/packed_propagation'
 
 describe "Enumerator::Lazy#take" do
   describe "value packing of source yields (matches Enumerable#take)" do
@@ -78,3 +79,12 @@
     end
   end
 end
+
+describe "Enumerator::Lazy#take" do
+  describe "propagating the source yield arity to a later stage" do
+    before :each do
+      @stage = -> e { e.take(12) }
+    end
+    it_behaves_like :enumerator_lazy_packed_propagation, nil
+  end
+end

core/enumerator/lazy/take_while_spec.rb

@@ -3,6 +3,7 @@
 require_relative '../../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative '../../enumerable/shared/value_packing'
+require_relative 'shared/packed_propagation'
 
 describe "Enumerator::Lazy#take_while" do
   describe "value packing of source yields (matches Enumerable#take_while)" do
@@ -66,3 +67,12 @@
     end
   end
 end
+
+describe "Enumerator::Lazy#take_while" do
+  describe "propagating the source yield arity to a later stage" do
+    before :each do
+      @stage = -> e { e.take_while { true } }
+    end
+    it_behaves_like :enumerator_lazy_packed_propagation, nil
+  end
+end