Fix issues with multiple string patterns on one line

Author: AndrewRadev

autoload/sj/python.vim

@@ -394,7 +394,7 @@ function! sj#python#SplitString()
     return 0
   endif
 
-  let string_pattern       = '\(\%(^\|[^\\]\)\zs\([''"]\)\).\{-}[^\\]\+\2'
+  let string_pattern       = '\%(^\|[^\\]\)\zs\([''"]\+\).\{-}[^\\]\1'
   let empty_string_pattern = '\%(''''\|""\)'
 
   let lineno = line('.')

spec/plugin/python_spec.rb

@@ -562,5 +562,29 @@ def example():
         """, three)
       EOF
     end
+
+    it "handles multiple strings on one line " do
+      set_file_contents 'string = "foo" + "bar"'
+
+      vim.search '"foo'
+      split
+
+      assert_file_contents <<~EOF
+        string = """
+            foo
+        """ + "bar"
+      EOF
+      join
+
+      vim.search '"bar'
+      split
+
+      assert_file_contents <<~EOF
+        string = "foo" + """
+            bar
+        """
+      EOF
+      join
+    end
   end
 end