Fix MatchData#values_at when passed index that is out of range

CHANGELOG.md

@@ -24,6 +24,7 @@ Compatibility:
 * Fix `Kernel#Complex` and raise exception when an argument is formatted incorrectly (#2765, @andrykonchin).
 * Add `#public?`, `#private?` and `#protected?` methods for `Method` and `UnboundMethod` classes (@andrykonchin).
 * Add optional argument to `Thread::Queue.new` (@andrykonchin).
+* Fix `MatchData#values_at` and handling indices that are out of range (#2783, @andrykonchin).
 
 Performance:
 

spec/ruby/core/matchdata/values_at_spec.rb

@@ -1,21 +1,76 @@
 require_relative '../../spec_helper'
 
-describe "MatchData#values_at" do
-  it "returns an array of the matching value" do
-    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0, 2, -2).should == ["HX1138", "X", "113"]
+describe "Struct#values_at" do
+  # Should be synchronized with core/array/values_at_spec.rb and core/struct/values_at_spec.rb
+  #
+  # /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").to_a # => ["HX1138", "H", "X", "113", "8"]
+
+  context "when passed a list of Integers" do
+    it "returns an array containing each value given by one of integers" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0, 2, -2).should == ["HX1138", "X", "113"]
+    end
+
+    it "returns nil value for any integer that is out of range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(5).should == [nil]
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(-6).should == [nil]
+    end
   end
 
-  describe "when passed a Range" do
-    it "returns an array of the matching value" do
-      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(2..4, 0..1).should == ["X", "113", "8", "HX1138", "H"]
+  context "when passed an integer Range" do
+    it "returns an array containing each value given by the elements of the range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0..2).should == ["HX1138", "H", "X"]
+    end
+
+    it "fills with nil values for range elements larger than the captured values number" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0..5).should == ["HX1138", "H", "X", "113", "8", nil]
+    end
+
+    it "raises RangeError if any element of the range is negative and out of range" do
+      -> { /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(-6..3) }.should raise_error(RangeError, "-6..3 out of range")
+    end
+
+    it "supports endless Range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0..).should == ["HX1138", "H", "X", "113", "8"]
+    end
+
+    it "supports beginningless Range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0..2).should == ["HX1138", "H", "X"]
+    end
+
+    it "returns an empty Array when Range is empty" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(2..0).should == []
+    end
+  end
+
+  context "when passed names" do
+    it 'slices captures with the given names' do
+      /(?<a>.)(?<b>.)(?<c>.)/.match('012').values_at(:c, :a).should == ['2', '0']
+    end
+
+    it 'slices captures with the given String names' do
+      /(?<a>.)(?<b>.)(?<c>.)/.match('012').values_at('c', 'a').should == ['2', '0']
     end
   end
 
-  it 'slices captures with the given names' do
-    /(?<a>.)(?<b>.)(?<c>.)/.match('012').values_at(:c, :a).should == ['2', '0']
+  it "supports multiple integer Ranges" do
+    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(1..2, 2..3).should == ["H", "X", "X", "113"]
   end
 
-  it 'takes names and indices' do
+  it "supports mixing integer Ranges and Integers" do
+    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(1..2, 4).should == ["H", "X", "8"]
+  end
+
+  it 'supports mixing of names and indices' do
     /\A(?<a>.)(?<b>.)\z/.match('01').values_at(0, 1, 2, :a, :b).should == ['01', '0', '1', '0', '1']
   end
+
+  it "returns a new empty Array if no arguments given" do
+    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at().should == []
+  end
+
+  it "fails when passed arguments of unsupported types" do
+    -> {
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(Object.new)
+    }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+  end
 end

src/main/ruby/truffleruby/core/regexp.rb

@@ -359,7 +359,36 @@ def inspect
   end
 
   def values_at(*indexes)
-    indexes.map { |i| self[i] }.flatten(1)
+    out = []
+    size = self.size
+
+    indexes.each do |elem|
+      if Primitive.object_kind_of?(elem, String) || Primitive.object_kind_of?(elem, Symbol)
+        out << self[elem]
+      elsif Primitive.object_kind_of?(elem, Range)
+        start, length = Primitive.range_normalized_start_length(elem, size)
+        finish = start + length - 1
+
+        raise RangeError, "#{elem} out of range" if start < 0
+        next if finish < start # ignore empty ranges
+
+        finish_in_bounds = [finish, size - 1].min
+        start.upto(finish_in_bounds) do |index|
+          out << self[index]
+        end
+
+        (finish_in_bounds + 1).upto(finish) { out << nil }
+      else
+        index = Primitive.rb_num2int(elem)
+        if index >= size || index < -size
+          out << nil
+        else
+          out << self[index]
+        end
+      end
+    end
+
+    out
   end
 
   def to_s