Don't mutate JSON.dump_default_options from dump

The use of Hash#update from the JSON.dump method was mutating the
dump_default_options hash on any call to dump with a limit provided. An
individual method call with an overriding value shouldn't update the
defaults in this way.

2 files changed, 7 insertions, 1 deletions

diff --git a/lib/json/common.rb b/lib/json/common.rb
index 426d933..32d9892 100644
--- a/lib/json/common.rb
+++ b/lib/json/common.rb
@@ -390,7 +390,7 @@ module JSON
       end
     end
     opts = JSON.dump_default_options
-    limit and opts.update(:max_nesting => limit)
+    opts = opts.merge(:max_nesting => limit) if limit
     result = generate(obj, opts)
     if anIO
       anIO.write result
diff --git a/tests/test_json.rb b/tests/test_json.rb
index 6af6b32..f4e6696 100755
--- a/tests/test_json.rb
+++ b/tests/test_json.rb
@@ -515,6 +515,12 @@ EOT
     assert_equal too_deep, output.string
   end
 
+  def test_dump_should_modify_defaults
+    max_nesting = JSON.dump_default_options[:max_nesting]
+    JSON.dump([], StringIO.new, 10)
+    assert_equal max_nesting, JSON.dump_default_options[:max_nesting]
+  end
+
   def test_big_integers
     json1 = JSON([orig = (1 << 31) - 1])
     assert_equal orig, JSON[json1][0]