Module:Escape

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This module is rated as ready for general use. It has reached a mature form and is thought to be relatively bug-free and ready for use wherever appropriate. It is ready to mention on help pages and other Wikipedia resources as an option for new users to learn. To reduce server load and bad output, it should be improved by sandbox testing rather than repeated trial-and-error editing.

This module is subject to page protection. It is a highly visible module in use by a very large number of pages, or is substituted very frequently. Because vandalism or mistakes would affect many pages, and even trivial editing might cause substantial load on the servers, it is protected from editing.

This Lua module is used on approximately 12,000 pages and changes may be widely noticed. Test changes in the module's /sandbox or /testcases subpages, or in your own module sandbox. Consider discussing changes on the talk page before implementing them.

Usage

This module is designed as an way to escape strings in a customized and efficient manner. It works by replacing characters that are preceded by your escape char (or phrase) There are two ways to call this module:

From another module:

local esc = require('Module:Escape')
esc:char(escape char (or sequence))
local to_escape = esc:text(string)
code that replaces or removes unescaped chars
local result = esc:undo(to_escape)

From a template:

{{#invoke:Escape|main|mode=function|char=escape char (or sequence)|text}}

In a template, the most useful function is kill.

This module is primarily intended to be used by other modules. However all functions can be called in template space using |mode=the function you want to call followed by arguments.

All module functions (i.e. any func. other than main()) should be called using a colon (:), e.g. esc:char('%') or esc:kill{'{{example|\\}}}', '}'} == '{{example|}'

escape:text() escape:text()	This function takes only one argument: A string. All characters in this string which are preceded by the sequence set by `escape:char()` will be replaced with placeholders that can be converted back into that char by escape:undo()
escape:undo() escape:undo()	Takes two arguments: The string that may contain placeholders set by `escape:text()` Optional, a char to be placed in front of any characters that have been de-escaped. (i.e. if you need to re-escape those string with a different char)
escape:kill() escape:kill()	This is basically equivalent to calling `string.gsub()` on the string returned by `escape:text()` and feeding that result into `escape:undo()` in a single step. Takes three arguments: A string A sequence of characters to be removed from that string. (May use a `string.gsub()` pattern) Optional, a char to be placed in front of any characters that have been de-escaped.
escape:char() escape:char()	This function's primary use is to initialize the patterns to scan a string for an escape/escaped sequence. It takes two arguments, the first being the escape character and the second being a table of arguments (optional). By default, this module will escape the `\` char. To escape the `{` char instead, you can do `require('Module:Escape'):char('{')` (or `esc:char('{')` (presuming you stored the table returned by this module in the local variable `esc`). When called without the second argument, char() will return a table containing the functions. This allows, for example, `escape:char(''):kill('123', '%d')` which would return '`2`'. For the most part, there is very little reason to set `\|mode=` in template space since the patterns it stores are not shared with other invokations of this module. Templates should instead use the `\|char=` if a new escape sequence is desired. Shortcut If provided a second argument that is a table containing a `{key = value}` pair, such that the key is `text`, `undo`, or `kill` and the value is a table containing the arguments that would have been passed to those functions. For example, `escape:char('\\', {text = 'string'})` is equivalent to `escape:char('\\'):text('string')`. Note that if multiple key-value pairs are provided, only one may execute. `kill` is ignored if either `text` or `undo` are present. `undo` is ignored if `text` is present.

Caveats

When using a multi-character escape sequence, this module only marks it using the byte value of the first character. Thus, escape:undo() will unescape, for example, all characters escaped with 'e' and 'esc' if both were used. In practice however this shouldn't be a problem as multiple escape sequences are pretty rare unless you're transitioning between multiple code languages. (Multiple multi-char escape sequences beginning with the same character are simply bad practice anyhow.)
Since byte values are stored as numbers, it is not recommended for you to use a number as an escape sequence (though it may work just fine).
Placeholder byte values separated with return ('\r') characters--chosen because they are seldom used at all, and virtually never used unpaired with '\n'; moreover, it is distinct from the markers generated by <nowiki>...</nowiki> or mw.text.nowiki() (which use the delete char). To set a different separator char, include the key-value pair {safeChr = alternate character} in the table that you pass to escape:char().

Speed

The following are benchmarks...

when executing the following module function:

 function p.test_kill500(frame)
  local esc = require('Module:Escape')
  for k = 1, 500 do
   local v = esc:kill(p.test_string2(), 'test')
  end
  return os.clock(esc)
 end

Lua error in Module:Escape/testcases at line 18: attempt to call method 'kill' (a nil value).

when repeating the following line 500 times in a template:

{{#invoke:Escape|main|mode=kill|{{#invoke:Escape/testcases|test_string2}}|test}}

0.767

All times in seconds. The module time x500 was calculated when you loaded this doc page (normally between 0.02 and 0.07). The template time x500 was recorded on Jan 15, 2015.

Examples

Template