Implement Array#fetch_values

[Feature #20702]

Works the same way than `Hash#fetch_values` for for array.

array.rb

@@ -210,4 +210,26 @@ class Array
       end
     end
   end
+
+  #  call-seq:
+  #    array.fetch_values(*indexes) -> new_array
+  #    array.fetch_values(*indexes) {|key| ... } -> new_array
+  #
+  #  Returns a new Array containing the values associated with the given indexes *indexes:
+  #    a = [:foo, :bar, :baz]
+  #    a.fetch_values(3, 1) # => [:baz, :foo]
+  #
+  #  Returns a new empty Array if no arguments given.
+  #
+  #  When a block is given, calls the block with each missing index,
+  #  treating the block's return value as the value for that index:
+  #    a = [:foo, :bar, :baz]
+  #    values = a.fetch_values(1, 0, 42, 777) {|index| index.to_s}
+  #    values # => [:bar, :foo, "42", "777"]
+  #
+  #  When no block is given, raises an exception if any given key is not found.
+  def fetch_values(*indexes, &block)
+    indexes.map! { |i| fetch(i, &block) }
+    indexes
+  end
 end

spec/ruby/core/array/fetch_values_spec.rb

@@ -0,0 +1,48 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#fetch_values" do
+  before :each do
+    @array = [:a, :b, :c]
+  end
+
+  ruby_version_is "3.4" do
+    describe "with matched indexes" do
+      it "returns the values for indexes" do
+        @array.fetch_values(0).should == [:a]
+        @array.fetch_values(0, 2).should == [:a, :c]
+      end
+
+      it "returns the values for indexes ordered in the order of the requested indexes" do
+        @array.fetch_values(2, 0).should == [:c, :a]
+      end
+    end
+
+    describe "with unmatched indexes" do
+      it "raises a index error if no block is provided" do
+        -> { @array.fetch_values(0, 1, 44) }.should raise_error(IndexError)
+      end
+
+      it "returns the default value from block" do
+        @array.fetch_values(44) { |index| "`#{index}' is not found" }.should == ["`44' is not found"]
+        @array.fetch_values(0, 44) { |index| "`#{index}' is not found" }.should == [:a, "`44' is not found"]
+      end
+    end
+
+    describe "without keys" do
+      it "returns an empty Array" do
+        @array.fetch_values.should == []
+      end
+    end
+
+    it "tries to convert the passed argument to an Integer using #to_int" do
+      obj = mock('to_int')
+      obj.should_receive(:to_int).and_return(2)
+      @array.fetch_values(obj).should == [:c]
+    end
+
+    it "raises a TypeError when the passed argument can't be coerced to Integer" do
+      -> { [].fetch_values("cat") }.should raise_error(TypeError)
+    end
+  end
+end