[GR-20313] Implement Enumerator::Chain#{initialize, initialize_copy, each, size, rewind, inspect}, Enumerator#+, and Enumerable#chain (#1859, #1858).

PullRequest: truffleruby/1209

Author: bjfish

CHANGELOG.md

@@ -71,6 +71,7 @@ Compatibility:
 * Implemented `rb_gc_register_mark_object` and `rb_enc_str_asciionly_p` (#1856, @chrisseaton).
 * Implemented `rb_io_set_nonblock` (#1741).
 * Include the major kernel version in `RUBY_PLATFORM` on macOS like MRI (#1860, @eightbitraptor).
+* Implemented `Enumerator::Chain`, `Enumerator#+`, and `Enumerable#chain` (#1859, #1858).
 
 Performance:
 

spec/tags/core/enumerable/chain_tags.txt

@@ -986,6 +986,10 @@ def sum(init = 0)
     end
   end
 
+  def chain(*enums)
+    Enumerator::Chain.new(self, *enums)
+  end
+
 end
 
 class Array

spec/tags/core/enumerator/chain/each_tags.txt

@@ -209,6 +209,10 @@ def feed(val)
     nil
   end
 
+  def +(other)
+    Enumerator::Chain.new(self, other)
+  end
+
   class Yielder
     def initialize(&block)
       raise LocalJumpError, 'Expected a block to be given' unless block_given?
@@ -561,4 +565,49 @@ class Enumerator::ArithmeticSequence < Enumerator
 end
 
 class Enumerator::Chain < Enumerator
+  def initialize(*args, &block)
+    TrufflePrimitive.check_frozen self
+    @enums = args.freeze
+    @pos = -1
+    self
+  end
+
+  def each
+    return to_enum :each unless block_given?
+    @enums.each_with_index do |enum, idx|
+      @pos = idx
+      enum.each do |*args|
+        yield(*args)
+      end
+    end
+  end
+
+  def size
+    total = 0
+    @enums.each do |e|
+      size = e.size
+      if size.nil? || (size.is_a?(Float) && size.infinite?)
+        return size
+      end
+      unless size.is_a?(Integer)
+        return nil
+      end
+      total += size
+    end
+    total
+  end
+
+  def rewind
+    while @pos >= 0
+      Truffle::Type.check_funcall(@enums[@pos], :rewind)
+      @pos -= 1
+    end
+    self
+  end
+
+  def inspect
+    return "#<#{self.class.name}: ...>" if Thread.detect_recursion(self) do
+      return "#<#{self.class.name}: #{@enums}>"
+    end
+  end
 end