Map To Side Effects, Vim plugin

This plugin helps to fool Vim into mapping key sequences in Normal, Visual/Select, and Operator-pending modes to function side effects.

"All problems in computer science can be solved by another level of indirection."

-- a quote believed by Diomidis Spinellis to be attributed to Butler Lampson, who attributes it to David Wheeler, according to Internet.

User interface (API)

This plugins supports 4 kinds of actions:

• Idempotent -- actions that take no arguments and cannot be meaningfully repeated more than once,
• Repeatable -- actions that take no arguments but can be meaningfully repeated a number of times,
• WithCount -- actions that take a count-type argument,
• WithCount1 -- actions that take a count1-type argument.

Action here means a VimL function called for its side effects.

Registering actions and creating mappings

The following functions create mappings of a key sequence of the form <Plug>(<name>) to the side effects of the given action in requested modes.

• mapToSideEffects#SetUpIdempotent(action[, options]) -- set up a mapping of a key sequence of the form <Plug>(<name>) to the side effects of a user provided Idempotent action, return the generated ID number,

• mapToSideEffects#SetUpRepeatable(action[, options]) -- set up a mapping of a key sequence of the form <Plug>(<name>) to the side effects of a user provided Repeatable action, return the generated ID number,

• mapToSideEffects#SetUpWithCount(action[, options]) -- set up a mapping of a key sequence of the form <Plug>(<name>) to the side effects of a user provided WithCount action, return the generated ID number,

• mapToSideEffects#SetUpWithCount1(action[, options]) -- set up a mapping of a key sequence of the form <Plug>(<name>) to the side effects of a user provided WithCount1 action, return the generated ID number,

The optional options argument of these functions must be a dictionary which can contain two keys: 'modes' and 'name'.

The modes option, if provided, has to be a string containing only letters n, v, x, s, o. If it is omitted, it is assumed to be 'nvo'.

The name option, if provided, has to be a string matching the regex '^[-_.:[:alnum:]]\{1,45}$' and not beginning with MapToSideEffects- in any character case, and the user must ensure that the key sequence <Plug>(<name>) has not yet been used as a mapping source. If the name option is omitted, the name is taken to be 'MapToSideEffects-<id>', where <id> is the generated numerical ID.

Name collisions may be avoided as follows, for example:

(a) start names with "<PluginName>-" in plugins and with a dash "-" in user scripts, or

(b) do not provide custom names, use automatic names of the form "MapToSideEffects-<id>."

NOTE: the reason for not allowing the hypothetical user to provide an arbitrary key sequence to be mapped to the action's side effects is the complexity, if not impossibility, of assuming the responsibility for deciding how and whether to "sanitize" the provided key sequence (which would make part of a string fed to execute command), how and whether to escape special characters, how and whether to allow the user to supply extra options to map commands (such as <special>, <silent>, etc.), as well as the apparent impossibility to properly address the possibility of the user's using <SID> as a part of his/her/theirs keys sequence.

Unregistering actions and removing mappings

The following functions unregister one or several previously registered actions and clear the corresponding mappings.

• mapToSideEffects#ClearOne(id) -- remove the mapping and the data associated with the given ID number,

• mapToSideEffects#ClearOneByName(name) -- remove the mapping and the data associated with the given name,

• mapToSideEffects#ClearMultiple(ids) -- remove the mappings and the data associated with the given ID numbers,

• mapToSideEffects#ClearMultipleByNames(names) -- remove the mappings and the data associated with the given names,

The following function removes all the plugin's data and clears the corresponding mappings.

• mapToSideEffects#Reset() -- remove all mappings and all data.

Usage

Suppose one wishes to use the key sequence <leader>ekf in Normal, Visual, and Operator-pending modes to perform the motion to the nearest "end of a keyword," as defined by the pattern '\>' in Vim, in the forward direction and taking into account the [count] prefix. Using this plugin, this can be achieved as follows, for example.

1. Define a function s:ToEndOfKeywordForward with desired side effects that takes a positive integer argument count1:

function s:ToEndOfKeywordForward(count1)
  let l:count1 = a:count1
  while l:count1 > 0
    call search('\>', 'W')
    let l:count1 -= 1
  endwhile
endfunction

2. Creates a mapping of <Plug>(-GoToEndOfKeywordForward) to the side effects of s:ToEndOfKeywordForward function in Normal, Visual, and Operator-pending modes:

call mapToSideEffects#SetUpWithCount1(
      \   function('s:ToEndOfKeywordForward'),
      \   {'name' : '-GoToEndOfKeywordForward', 'modes' : 'nxo'} )

3. Create desired custom mappings to <Plug>(-GoToEndOfKeywordForward):

nmap <leader>ekf <Plug>(-GoToEndOfKeywordForward)
xmap <leader>ekf <Plug>(-GoToEndOfKeywordForward)
omap <leader>ekf <Plug>(-GoToEndOfKeywordForward)