Switch Vim string styles, apply a minor python fix

Author: AndrewRadev

ftplugin/vim/switch.vim

@@ -5,4 +5,5 @@ endif
 let b:switch_definitions =
       \ [
       \   g:switch_builtins.vim_script_local_function,
+      \   g:switch_builtins.vim_string_style,
       \ ]

plugin/switch.vim

@@ -228,6 +228,11 @@ let g:switch_builtins =
       \     '\<s:\(\h\w\+\)(':  '<SID>\1(',
       \     '<SID>\(\h\w\+\)(': 's:\1(',
       \   },
+      \   'vim_string_style': {
+      \     '\$"\(\%([^"\\]\|\\.\)*\)"':              '''\1''',
+      \     '''\(\%([^''\\]\|\\.\)*\)''':             '"\1"',
+      \     '\%([^$]\|^\)\zs"\(\%([^"\\]\|\\.\)*\)"': '$"\1"',
+      \   },
       \   'markdown_task_item': {
       \     '^\(\s*\)- \[ \] \(.*\)':  '\1- [x] \2',
       \     '^\(\s*\)- \[x\] \(.*\)':  '\1- [ ] \2',
@@ -254,9 +259,9 @@ let g:switch_builtins =
       \     },
       \   },
       \   'python_string_style': {
-      \     'f"\(\%([^"\\]\|\\.\)*\)"':    '''\1''',
-      \     '''\(\%([^''\\]\|\\.\)*\)''':  '"\1"',
-      \     'f\@!"\(\%([^"\\]\|\\.\)*\)"': 'f"\1"',
+      \     'f"\(\%([^"\\]\|\\.\)*\)"':                '''\1''',
+      \     '''\(\%([^''\\]\|\\.\)*\)''':              '"\1"',
+      \     '\%\([^f]\|^\)\zs"\(\%([^"\\]\|\\.\)*\)"': 'f"\1"',
       \   },
       \   'python_asserts': {
       \     '\<assertTrue\>':      'assertFalse',

spec/plugin/vim_spec.rb

@@ -18,4 +18,17 @@
       call s:TestFunction()
     EOF
   end
+
+  specify "string type" do
+    set_file_contents 'let foo = "bar?"'
+
+    vim.search('bar').switch
+    assert_file_contents 'let foo = $"bar?"'
+
+    vim.switch
+    assert_file_contents "let foo = 'bar?'"
+
+    vim.switch
+    assert_file_contents 'let foo = "bar?"'
+  end
 end