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A simple Vim plugin to switch segments of text with predefined replacements

branch: master
README.md

Build Status

Screencast!

This plugin is easier to demonstrate than explain. You can find a screencast here.

Usage

The main entry point of the plugin is a single command, :Switch. When the command is executed, the plugin looks for one of a few specific patterns under the cursor and performs a substition depending on the pattern. For example, if the cursor is on the "true" in the following code:

flag = true

Then, upon executing :Switch, the "true" will turn into "false".

It is highly recommended to map the :Switch command to a key. For example, to map it to "-", place the following in your .vimrc:

nnoremap - :Switch<cr>

See the "customization" section below for information on how to create several mappings with different definitions.

There are three main principles that the substition follows:

  1. The cursor needs to be on the match. Regardless of the pattern, the plugin only performs the substition if the cursor is positioned in the matched text.

  2. When several patterns match, the shortest match is performed. For example, in ruby, the following switch is defined:

    { :foo => true }
    # switches into:
    { foo: true }
    

    This works if the cursor is positioned somewhere on the ":foo =>" part, but if it's on top of "true", the abovementioned true -> false substition will be performed instead. If you want to perform a "larger" substition instead, you could move your cursor away from the "smaller" match. In this case, move the cursor away from the "true" keyword.

  3. When several patterns with the same size match, the order of the definitions is respected. For instance, in eruby, the following code can be transformed:

    <% if foo? %>
    could switch into:
    <%# if foo? %>
    but instead, it would switch into:
    <% if true or (foo?) %>
    

    The second switch will be performed, simply because in the definition list, the pattern was placed at a higher spot. In this case, this seems to make sense to prioritize one over the other. If it's needed to prioritize in a different way, the definition list should be redefined by the user.

Customization

There are two variables that hold the global definition list and the buffer-local definition list -- g:switch_definitions and b:switch_definitions, respectively. These contain the definitions for the built-ins provided by the plugin. In order to add the switches you want, you should override g:switch_custom_definitions and b:switch_custom_definitions instead.

The format of the variables is a simple List of items. Each item can be either a List or a Dict.

List definitions

let g:switch_custom_definitions =
    \ [
    \   ['foo', 'bar', 'baz']
    \ ]

With this definition list, if the plugin encounters "foo" under the cursor, it will be changed to "bar". If it sees "bar", it will change it to "baz", and "baz" would be turned into "foo". This is the simple case of a definition that is implemented (in a slightly different way) by the "toggle.vim" plugin.

The more complicated (and more powerful) way to define a switch pattern is by using a Dict.

Dict definitions

autocmd FileType eruby let b:switch_custom_definitions =
    \ [
    \   {
    \     ':\(\k\+\)\s\+=>': '\1:',
    \     '\<\(\k\+\):':     ':\1 =>',
    \   },
    \ ]

When in the eruby filetype, the hash will take effect. The plugin will look for something that looks like :foo => and replace it with foo:, or the reverse -- foo:, so it could turn it into :foo =>. The search string is fed to the search() function, so all special patterns like \%l have effect in it. And the replacement string is used in the :substitute command, so all of its replacement patterns work as well.

Notice the use of autocmd FileType eruby to set the buffer-local variable whenever an eruby file is loaded. The same effect could be achieved by placing this definition in ftplugin/eruby.vim.

Another interesting example is the following definition:

autocmd FileType php let b:switch_custom_definitions =
      \ [
      \   {
      \     '<?php echo \(.\{-}\) ?>':        '<?php \1 ?>',
      \     '<?php \%(echo\)\@!\(.\{-}\) ?>': '<?php echo \1 ?>',
      \   }
      \ ]

In this case, when in the "php" filetype, the plugin will attempt to remove the "echo" in "<?php echo 'something' ?>" or vice-versa. However, the second pattern wouldn't work properly if it didn't contain "\%(echo)\@!". This pattern asserts that, in this place of the text, there is no "echo". Otherwise, the second pattern would match as well. Using the \@! pattern in strategic places is important in many cases.

For even more complicated substitions, you can use the nested form.

Nested dict definitions

The following expression replaces underscored identifier names with their camelcased versions.

let b:switch_custom_definitions = [
      \   {
      \     '\<[a-z0-9]\+_\k\+\>': {
      \       '_\(.\)': '\U\1'
      \     },
      \     '\<[a-z0-9]\+[A-Z]\k\+\>': {
      \       '\([A-Z]\)': '_\l\1'
      \     },
      \   }
      \ ]

If the cursor is on "foo_bar_baz", then switching would produce "fooBarBaz" and vice-versa. The logic is as follows:

  • The keys of the dict are patterns, just like the "normal" dict version.
  • The values of the dict are dicts with patterns for keys and replacements for values.

The goal of this form is to enable substituting several different kinds of patterns within the limits of another one. In this example, there's no way to define this switch using the simpler form, since there's an unknown number of underscores in the variable name and all of them need to be replaced in order to make the switch complete.

The nested patterns differ from the simple one in that each one of them is replaced globally, only within the limits of the "parent" pattern.

Note that this particular example is NOT included as a built-in, since it may overshadow other ones and is probably not that useful, either (it's rare that a language would require changing between the two forms). An example usage may be within javascript, if your server-side variables are underscored and the client-side ones need to be camelcased. For something more complete, you can take a look at this gist.

You could also use a separate mapping for that.

Separate mappings

While it was recommended to define a mapping for :Switch, you could actually define several mappings with your own custom definitions:

let g:variable_style_switch_definitions = [
      \   {
      \     '\<[a-z0-9]\+_\k\+\>': {
      \       '_\(.\)': '\U\1'
      \     },
      \     '\<[a-z0-9]\+[A-Z]\k\+\>': {
      \       '\([A-Z]\)': '_\l\1'
      \     },
      \   }
      \ ]
nnoremap + :call switch#Switch(g:variable_style_switch_definitions)<cr>
nnoremap - :Switch<cr>

With this, typing - would invoke the built-in switch definitions, while typing + would switch between camelcase and underscored variable styles. This may be particularly useful if you have several clashing switches on patterns that match similar things.

Builtins

Here's a list of all the built-in switch definitions. To see the actual definitions with their patterns and replacements, look at the file plugin/switch.vim.

Global

  • Boolean conditions:

    foo && bar
    foo || bar
    
  • Boolean constants:

    flag = true
    flag = false
    
    flag = True
    flag = False
    

Ruby

  • Hash style:

    foo = { :one => 'two' }
    foo = { one: 'two' }
    
  • If-clauses:

    if predicate?
      puts 'Hello, World!'
    end
    
    if true or (predicate?)
      puts 'Hello, World!'
    end
    
    if false and (predicate?)
      puts 'Hello, World!'
    end
    
  • Rspec should/should_not:

    1.should eq 1
    1.should_not eq 1
    
  • Tap:

    foo = user.comments.map(&:author).first
    foo = user.comments.tap { |o| puts o.inspect }.map(&:author).first
    
  • String style:

    foo = 'bar'
    foo = "baz"
    foo = :baz
    

    (Note that it only works for single-word strings.)

  • Ruby block shorthands:

    do_something { |x| x.some_work! }
    do_something(&:some_work!)
    
  • Array shorthands:

    ['one', 'two', 'three']
    %w(one two three)
    

    (In this case, be careful to not have the cursor on one of the strings, or you'll trigger the string switch as seen above.)

PHP "echo" in tags:

<?php "Text" ?>
<?php echo "Text" ?>

Eruby

  • If-clauses:

    <% if predicate? %>
      <%= 'Hello, World!' %>
    <% end %>
    
    <% if true or (predicate?) %>
      <%= 'Hello, World!' %>
    <% end %>
    
    <% if false and (predicate?) %>
      <%= 'Hello, World!' %>
    <% end %>
    
  • Tag type:

    <% something %>
    <%# something %>
    <%= something %>
    
  • Hash style:

    <% foo = { :one => 'two' } %>
    <% foo = { one: 'two' } %>
    

Haml

  • If-clauses:

    - if predicate?
      Hello, World!
    
    - if true or (predicate?)
      Hello, World!
    
    - if false and (predicate?)
      Hello, World!
    
  • Tag type:

    - something
    -# something
    = something
    
  • Hash style:

    %a{:href => '/example'}
    %a{href: '/example'}
    

C++ pointer dots/arrows:

Object* foo = bar.baz;
Object* foo = bar->baz;

Coffeescript arrows

functionCall (foo) ->
functionCall (foo) =>

Clojure

  • String style:

    "baz"
    'bar
    :baz
    

    (Note that it only works for single-word strings, such as baz, b-a-z, or **.)

  • If-clauses:

    (if predicate?
      (prn "Hello, world!")
      (prn "oh..."))
    
    (if (or true predicate?)
      (prn "Hello, world!")
      (prn "oh..."))
    
    (if (and false predicate?)
      (prn "Hello, world!")
      (prn "oh..."))
    

    (Note that it also works for if-not, when, and when-not.)

Scala

  • String style: scala "foo bar" s"foo bar" f"foo bar" """foo bar""" s"""foo bar""" f"""foo bar"""

Similar work

This plugin is very similar to two other ones:

Both of these work on replacing a specific word under the cursor with a different one. The benefit of switch.vim is that it works for much more complicated patterns. The drawback is that this makes extending it more involved. I encourage anyone that doesn't need the additional power in switch.vim to take a look at one of these two.

Contributing

If you'd like to hack on the plugin, please see CONTRIBUTING.md first.

Issues

Any issues and suggestions are very welcome on the github bugtracker.

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