From 9773b36e7468e7649ab3f01cf88c154dad265e55 Mon Sep 17 00:00:00 2001
From: Sampo Kuokkanen <sampo.kuokkanen@gmail.com>
Date: Fri, 29 May 2026 16:05:11 +0900
Subject: [PATCH] Add specs for #each passing source yields by block arity
 (Enumerator and Lazy)

Unlike the Enumerable collection methods, which pack yielded source values via
rb_enum_values_pack() (0 args -> nil, 1 arg -> the value, N args -> Array), #each
passes them to the block by ordinary block arity (rb_yield_values2() in CRuby):
a single-argument block receives the first value, a multi-argument block
destructures, and a splat block gathers them.

Pin this explicitly via a shared describe used by both Enumerator#each and
Enumerator::Lazy#each, complementing the value_packing specs.
---
 core/enumerator/each_spec.rb      |  8 ++++++
 core/enumerator/lazy/each_spec.rb | 11 ++++++++
 core/enumerator/shared/each.rb    | 46 +++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+)
 create mode 100644 core/enumerator/lazy/each_spec.rb
 create mode 100644 core/enumerator/shared/each.rb

diff --git a/core/enumerator/each_spec.rb b/core/enumerator/each_spec.rb
index 03be53fe0..baab987dd 100644
--- a/core/enumerator/each_spec.rb
+++ b/core/enumerator/each_spec.rb
@@ -1,6 +1,14 @@
 require_relative '../../spec_helper'
+require_relative 'shared/each'
 
 describe "Enumerator#each" do
+  describe "passing source-yielded arguments to the block" do
+    before :each do
+      @object = -> e { e }
+    end
+    it_behaves_like :enum_each, nil
+  end
+
   before :each do
     object_each_with_arguments = Object.new
     def object_each_with_arguments.each_with_arguments(arg, *args)
diff --git a/core/enumerator/lazy/each_spec.rb b/core/enumerator/lazy/each_spec.rb
new file mode 100644
index 000000000..3d44d230d
--- /dev/null
+++ b/core/enumerator/lazy/each_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../../spec_helper'
+require_relative '../shared/each'
+
+describe "Enumerator::Lazy#each" do
+  describe "passing source-yielded arguments to the block (matches Enumerator#each)" do
+    before :each do
+      @object = -> e { e.lazy }
+    end
+    it_behaves_like :enum_each, nil
+  end
+end
diff --git a/core/enumerator/shared/each.rb b/core/enumerator/shared/each.rb
new file mode 100644
index 000000000..18ca77320
--- /dev/null
+++ b/core/enumerator/shared/each.rb
@@ -0,0 +1,46 @@
+# #each passes source-yielded values to the block by ordinary block arity
+# (rb_yield_values2 semantics in CRuby), unlike the Enumerable collection methods
+# which pack them via rb_enum_values_pack() (see enumerable/shared/value_packing.rb).
+describe :enum_each, shared: true do
+  # @object must be set to a Proc that wraps an Enumerator into the receiver
+  # under test (e.g. -> e { e } for Enumerator#each, -> e { e.lazy } for Lazy#each).
+  describe "with a source that yields multiple values" do
+    before :each do
+      @enum = @object.call(Enumerator.new { |y| y.yield 1, 2; y.yield 3, 4 })
+    end
+
+    it "yields the first value to a single-argument block" do
+      collected = []
+      @enum.each { |x| collected << x }
+      collected.should == [1, 3]
+    end
+
+    it "yields each value to a multi-argument block" do
+      collected = []
+      @enum.each { |x, y| collected << [x, y] }
+      collected.should == [[1, 2], [3, 4]]
+    end
+
+    it "gathers the values for a splat block" do
+      collected = []
+      @enum.each { |*args| collected << args }
+      collected.should == [[1, 2], [3, 4]]
+    end
+  end
+
+  describe "with a source that yields a single value" do
+    it "yields the value to a single-argument block" do
+      collected = []
+      @object.call(Enumerator.new { |y| y.yield 7; y.yield 8 }).each { |x| collected << x }
+      collected.should == [7, 8]
+    end
+  end
+
+  describe "with a source that yields no value" do
+    it "yields nil to a single-argument block" do
+      collected = []
+      @object.call(Enumerator.new { |y| y.yield; y.yield }).each { |x| collected << x }
+      collected.should == [nil, nil]
+    end
+  end
+end