Fix tuple regex

Author: AndrewRadev

autoload/sj/python.vim

@@ -88,7 +88,7 @@ function! sj#python#SplitTuple()
 endfunction
 
 function! sj#python#JoinTuple()
-  return s:JoinList('([^)]*\s*$', '(', ')')
+  return s:JoinList('([^()]*\s*$', '(', ')')
 endfunction
 
 function! sj#python#SplitImport()

spec/plugin/python_spec.rb

@@ -6,6 +6,9 @@
   before :each do
     vim.set(:expandtab)
     vim.set(:shiftwidth, 4)
+
+    vim.command 'unlet! b:splitjoin_python_import_style'
+    vim.command 'unlet! b:splitjoin_python_brackets_on_separate_lines'
   end
 
   specify "dictionaries" do
@@ -282,6 +285,30 @@ def example():
     EOF
   end
 
+  specify "tuple within tuple" do
+    set_file_contents <<~EOF
+      out = Foo(Bar(baz, bla))
+    EOF
+
+    vim.command 'let b:splitjoin_python_brackets_on_separate_lines = 1'
+    vim.search('baz')
+    split
+
+    assert_file_contents <<~EOF
+      out = Foo(Bar(
+          baz,
+          bla
+          ))
+    EOF
+
+    vim.search('Bar\zs(')
+    join
+
+    assert_file_contents <<~EOF
+      out = Foo(Bar(baz, bla))
+    EOF
+  end
+
   specify "list comprehensions" do
     pending "Old version on CI" if ENV['CI']