* lib/csv.rb: Optimize header hashes by freezing string keys.

  [ruby-core:58510]



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43825 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 25 insertions, 1 deletions

diff --git a/test/csv/test_interface.rb b/test/csv/test_interface.rb
index ad310fae49..22907d2dd0 100755
--- a/test/csv/test_interface.rb
+++ b/test/csv/test_interface.rb
@@ -198,6 +198,25 @@ class TestCSV::Interface < TestCSV
     end
   end
 
+  def test_write_hash_with_string_keys
+    File.unlink(@path)
+
+    lines = [{a: 1, b: 2, c: 3}, {a: 4, b: 5, c: 6}]
+    CSV.open( @path, "wb", headers: true ) do |csv|
+      csv << lines.first.keys
+      lines.each { |line| csv << line }
+    end
+    CSV.open( @path, "rb", headers: true ) do |csv|
+      csv.each do |line|
+        csv.headers.each_with_index do |header, h|
+          keys = line.to_hash.keys
+          assert_instance_of(String, keys[h])
+          assert_same(header, keys[h])
+        end
+      end
+    end
+  end
+
   def test_write_hash_with_headers_array
     File.unlink(@path)
 
diff --git a/test/csv/test_row.rb b/test/csv/test_row.rb
index 697c7d56c8..a097fc7200 100755
--- a/test/csv/test_row.rb
+++ b/test/csv/test_row.rb
@@ -297,7 +297,12 @@ class TestCSV::Row < TestCSV
   end
 
   def test_to_hash
-    assert_equal({"A" => nil, "B" => 2, "C" => 3}, @row.to_hash)
+    hash = @row.to_hash
+    assert_equal({"A" => nil, "B" => 2, "C" => 3}, hash)
+    hash.keys.each_with_index do |string_key, h|
+      assert_predicate(string_key, :frozen?)
+      assert_same(string_key, @row.headers[h])
+    end
   end
 
   def test_to_csv