Module:String: Difference between revisions

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local str = {}
--[[
 
This module is intended to provide access to basic string functions.
 
Most of the functions provided here can be invoked with named parameters,
unnamed parameters, or a mixture.  If named parameters are used, Mediawiki will
automatically remove any leading or trailing whitespace from the parameter.
Depending on the intended use, it may be advantageous to either preserve or
remove such whitespace.


-- Cannot include null byte.
Global options
local UTF8_char = "[\1-\127\194-\244][\128-\191]*"
    ignore_errors: If set to 'true' or 1, any error condition will result in
        an empty string being returned rather than an error message.


--[[
    error_category: If an error occurs, specifies the name of a category to
ulen
        include with the error message.  The default category is
        [Category:Errors reported by Module String].


Counts UTF-8 characters. Faster than mw.ustring.len.
    no_category: If set to 'true' or 1, no category will be added if an error
        is generated.


Assumes that the encoding is correct. Unlike mw.ustring.len, does not return nil
Unit tests for this module are available at Module:String/tests.
if encoding is invalid.
]]


Does not count the bytes 192, 193, and 245-255. They are not used in UTF-8 and
local str = {}
will not occur if the string is valid. They are replaced with the replacement
character (U+FFFD) on MediaWiki pages.
--]]
function str.ulen(text)
local _, length = string.gsub(text, UTF8_char, "")
return length
end


--[[
--[[
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Usage:
Usage:
{{#invoke:string|len|target_string|}}
{{#invoke:String|len|target_string|}}
OR
OR
{{#invoke:string|len|s=target_string}}
{{#invoke:String|len|s=target_string}}


Parameters
Parameters
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trailing whitespace from the target string.
trailing whitespace from the target string.
]]
]]
function str.len(frame)
function str.len( frame )
local new_args = str._getParameters(frame.args, { 's' });
local new_args = str._getParameters( frame.args, {'s'} )
local s = new_args['s'] or '';
local s = new_args['s'] or ''
return mw.ustring.len(s)
return mw.ustring.len( s )
end
end


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Usage:
Usage:
{{#invoke:string|sub|target_string|start_index|end_index}}
{{#invoke:String|sub|target_string|start_index|end_index}}
OR
OR
{{#invoke:string|sub|s=target_string|i=start_index|j=end_index}}
{{#invoke:String|sub|s=target_string|i=start_index|j=end_index}}


Parameters
Parameters
     s: The string to return a subset of
     s: The string to return a subset of
     i: The fist index of the substring to return, defaults to 1.
     i: The first index of the substring to return, defaults to 1.
     j: The last index of the string to return, defaults to the last character.
     j: The last index of the string to return, defaults to the last character.
   
 
The first character of the string is assigned an index of 1.  If either i or j
The first character of the string is assigned an index of 1.  If either i or j
is a negative value, it is interpreted the same as selecting a character by
is a negative value, it is interpreted the same as selecting a character by
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reported.
reported.
]]
]]
function str.sub(frame)
function str.sub( frame )
local new_args = str._getParameters(frame.args, { 's', 'i', 'j' });
local new_args = str._getParameters( frame.args, { 's', 'i', 'j' } )
local s = new_args['s'] or '';
local s = new_args['s'] or ''
local i = tonumber(new_args['i']) or 1;
local i = tonumber( new_args['i'] ) or 1
local j = tonumber(new_args['j']) or -1;
local j = tonumber( new_args['j'] ) or -1
 
local len = mw.ustring.len(s);
local len = mw.ustring.len( s )
 
-- Convert negatives for range checking
-- Convert negatives for range checking
if i < 0 then
if i < 0 then
i = len + i + 1;
i = len + i + 1
end
end
if j < 0 then
if j < 0 then
j = len + j + 1;
j = len + j + 1
end
end
 
if i > len or j > len or i < 1 or j < 1 then
if i > len or j > len or i < 1 or j < 1 then
return str._error('String subset index out of range');
return str._error( 'String subset index out of range' )
end
end
if j < i then
if j < i then
return str._error('String subset indices out of order');
return str._error( 'String subset indices out of order' )
end
end
 
return mw.ustring.sub(s, i, j)
return mw.ustring.sub( s, i, j )
end
end


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to maintain these older templates.
to maintain these older templates.
]]
]]
function str.sublength(frame)
function str.sublength( frame )
local i = tonumber(frame.args.i) or 0
local i = tonumber( frame.args.i ) or 0
local len = tonumber(frame.args.len)
local len = tonumber( frame.args.len )
return mw.ustring.sub(frame.args.s, i + 1, len and (i + len))
return mw.ustring.sub( frame.args.s, i + 1, len and ( i + len ) )
end
end


--[[
--[[
match
_match


This function returns a substring from the source string that matches a
This function returns a substring from the source string that matches a
specified pattern.
specified pattern. It is exported for use in other modules


Usage:
Usage:
{{#invoke:string|match|source_string|pattern_string|start_index|match_number|plain_flag|nomatch_output}}
strmatch = require("Module:String")._match
OR
sresult = strmatch( s, pattern, start, match, plain, nomatch )
{{#invoke:string|pos|s=source_string|pattern=pattern_string|start=start_index
    |match=match_number|plain=plain_flag|nomatch=nomatch_output}}


Parameters
Parameters
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         text.  Defaults to false.
         text.  Defaults to false.
     nomatch: If no match is found, output the "nomatch" value rather than an error.
     nomatch: If no match is found, output the "nomatch" value rather than an error.
If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from each string.  In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.
If the match_number or start_index are out of range for the string being queried, then
this function generates an error.  An error is also generated if no match is found.
If one adds the parameter ignore_errors=true, then the error will be suppressed and
an empty string will be returned on any failure.


For information on constructing Lua patterns, a form of [regular expression], see:
For information on constructing Lua patterns, a form of [regular expression], see:
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]]
]]
function str.match(frame)
-- This sub-routine is exported for use in other modules
local new_args = str._getParameters(frame.args, { 's', 'pattern', 'start', 'match', 'plain', 'nomatch' });
function str._match( s, pattern, start, match_index, plain_flag, nomatch )
local s = new_args['s'] or '';
local start = tonumber(new_args['start']) or 1;
local plain_flag = str._getBoolean(new_args['plain'] or false);
local pattern = new_args['pattern'] or '';
local match_index = math.floor(tonumber(new_args['match']) or 1);
local nomatch = new_args['nomatch'];
if s == '' then
if s == '' then
return str._error('Target string is empty');
return str._error( 'Target string is empty' )
end
end
if pattern == '' then
if pattern == '' then
return str._error('Pattern string is empty');
return str._error( 'Pattern string is empty' )
end
end
if math.abs(start) < 1 or math.abs(start) > mw.ustring.len(s) then
start = tonumber(start) or 1
return str._error('Requested start is out of range');
if math.abs(start) < 1 or math.abs(start) > mw.ustring.len( s ) then
return str._error( 'Requested start is out of range' )
end
end
if match_index == 0 then
if match_index == 0 then
return str._error('Match index is out of range');
return str._error( 'Match index is out of range' )
end
end
if plain_flag then
if plain_flag then
pattern = str.pattern_escape(pattern);
pattern = str._escapePattern( pattern )
end
end
 
local result
local result
if match_index == 1 then
if match_index == 1 then
-- Find first match is simple case
-- Find first match is simple case
result = mw.ustring.match(s, pattern, start)
result = mw.ustring.match( s, pattern, start )
else
else
if start > 1 then
if start > 1 then
s = mw.ustring.sub(s, start);
s = mw.ustring.sub( s, start )
end
end
 
local iterator = mw.ustring.gmatch(s, pattern);
local iterator = mw.ustring.gmatch(s, pattern)
if match_index > 0 then
if match_index > 0 then
-- Forward search
-- Forward search
for w in iterator do
for w in iterator do
match_index = match_index - 1;
match_index = match_index - 1
if match_index == 0 then
if match_index == 0 then
result = w;
result = w
break;
break
end
end
end
end
else
else
-- Reverse search
-- Reverse search
local result_table = {};
local result_table = {}
local count = 1;
local count = 1
for w in iterator do
for w in iterator do
result_table[count] = w;
result_table[count] = w
count = count + 1;
count = count + 1
end
end
 
result = result_table[count + match_index];
result = result_table[ count + match_index ]
end
end
end
end
 
if result == nil then
if result == nil then
if nomatch == nil then
if nomatch == nil then
return str._error('Match not found');
return str._error( 'Match not found' )
else
else
return nomatch;
return nomatch
end
end
else
else
return result;
return result
end
end
end
--[[
match
This function returns a substring from the source string that matches a
specified pattern.
Usage:
{{#invoke:String|match|source_string|pattern_string|start_index|match_number|plain_flag|nomatch_output}}
OR
{{#invoke:String|match|s=source_string|pattern=pattern_string|start=start_index
    |match=match_number|plain=plain_flag|nomatch=nomatch_output}}
Parameters
    s: The string to search
    pattern: The pattern or string to find within the string
    start: The index within the source string to start the search.  The first
        character of the string has index 1.  Defaults to 1.
    match: In some cases it may be possible to make multiple matches on a single
        string.  This specifies which match to return, where the first match is
        match= 1.  If a negative number is specified then a match is returned
        counting from the last match.  Hence match = -1 is the same as requesting
        the last match.  Defaults to 1.
    plain: A flag indicating that the pattern should be understood as plain
        text.  Defaults to false.
    nomatch: If no match is found, output the "nomatch" value rather than an error.
If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from each string.  In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.
If the match_number or start_index are out of range for the string being queried, then
this function generates an error.  An error is also generated if no match is found.
If one adds the parameter ignore_errors=true, then the error will be suppressed and
an empty string will be returned on any failure.
For information on constructing Lua patterns, a form of [regular expression], see:
* http://www.lua.org/manual/5.1/manual.html#5.4.1
* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Patterns
* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Ustring_patterns
]]
-- This is the entry point for #invoke:String|match
function str.match( frame )
local new_args = str._getParameters( frame.args, {'s', 'pattern', 'start', 'match', 'plain', 'nomatch'} )
local s = new_args['s'] or ''
local start = tonumber( new_args['start'] ) or 1
local plain_flag = str._getBoolean( new_args['plain'] or false )
local pattern = new_args['pattern'] or ''
local match_index = math.floor( tonumber(new_args['match']) or 1 )
local nomatch = new_args['nomatch']
return str._match( s, pattern, start, match_index, plain_flag, nomatch )
end
end


Line 218: Line 260:


Usage:
Usage:
{{#invoke:string|pos|target_string|index_value}}
{{#invoke:String|pos|target_string|index_value}}
OR
OR
{{#invoke:string|pos|target=target_string|pos=index_value}}
{{#invoke:String|pos|target=target_string|pos=index_value}}


Parameters
Parameters
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A requested value of zero, or a value greater than the length of the string returns an error.
A requested value of zero, or a value greater than the length of the string returns an error.
]]
]]
function str.pos(frame)
function str.pos( frame )
local new_args = str._getParameters(frame.args, { 'target', 'pos' });
local new_args = str._getParameters( frame.args, {'target', 'pos'} )
local target_str = new_args['target'] or '';
local target_str = new_args['target'] or ''
local pos = tonumber(new_args['pos']) or 0;
local pos = tonumber( new_args['pos'] ) or 0
 
if pos == 0 or math.abs(pos) > mw.ustring.len(target_str) then
if pos == 0 or math.abs(pos) > mw.ustring.len( target_str ) then
return str._error('String index out of range');
return str._error( 'String index out of range' )
end
end
 
return mw.ustring.sub(target_str, pos, pos);
return mw.ustring.sub( target_str, pos, pos )
end
end


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separatetly.
separatetly.
]]
]]
function str.str_find(frame)
function str.str_find( frame )
local new_args = str._getParameters(frame.args, { 'source', 'target' });
local new_args = str._getParameters( frame.args, {'source', 'target'} )
local source_str = new_args['source'] or '';
local source_str = new_args['source'] or ''
local target_str = new_args['target'] or '';
local target_str = new_args['target'] or ''
 
if target_str == '' then
if target_str == '' then
return 1;
return 1
end
end
 
local start = mw.ustring.find(source_str, target_str, 1, true)
local start = mw.ustring.find( source_str, target_str, 1, true )
if start == nil then
if start == nil then
start = -1
start = -1
end
end
 
return start
return start
end
end
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Usage:
Usage:
{{#invoke:string|find|source_str|target_string|start_index|plain_flag}}
{{#invoke:String|find|source_str|target_string|start_index|plain_flag}}
OR
OR
{{#invoke:string|find|source=source_str|target=target_str|start=start_index|plain=plain_flag}}
{{#invoke:String|find|source=source_str|target=target_str|start=start_index|plain=plain_flag}}


Parameters
Parameters
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This function returns the first index >= "start" where "target" can be found
This function returns the first index >= "start" where "target" can be found
within "source".  Indices are 1-based.  If "target" is not found, then this
within "source".  Indices are 1-based.  If "target" is not found, then this
function returns an empty string.  If either "source" or "target" are missing / empty, this
function returns 0.  If either "source" or "target" are missing / empty, this
function also returns an empty string.
function also returns 0.


This function should be safe for UTF-8 strings.
This function should be safe for UTF-8 strings.
]]
]]
function str.find(frame)
function str.find( frame )
local params = {
local new_args = str._getParameters( frame.args, {'source', 'target', 'start', 'plain' } )
[1] = { required = true },
local source_str = new_args['source'] or ''
[2] = { required = true },
local pattern = new_args['target'] or ''
[3] = { type = "number" },
local start_pos = tonumber(new_args['start']) or 1
[4] = { type = "boolean" },
local plain = new_args['plain'] or true
}
 
if source_str == '' or pattern == '' then
local args = require("Module:parameters").process(frame.args, params)
return 0
end
return mw.ustring.find(args[1], args[2], args[3], args[4])
 
plain = str._getBoolean( plain )
 
local start = mw.ustring.find( source_str, pattern, start_pos, plain )
if start == nil then
start = 0
end
 
return start
end
end


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Usage:
Usage:
{{#invoke:string|replace|source_str|pattern_string|replace_string|replacement_count|plain_flag}}
{{#invoke:String|replace|source_str|pattern_string|replace_string|replacement_count|plain_flag}}
OR
OR
{{#invoke:string|replace|source=source_string|pattern=pattern_string|replace=replace_string|
{{#invoke:String|replace|source=source_string|pattern=pattern_string|replace=replace_string|
   count=replacement_count|plain=plain_flag}}
   count=replacement_count|plain=plain_flag}}


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         text and not as a Lua style regular expression, defaults to true
         text and not as a Lua style regular expression, defaults to true
]]
]]
function str.replace(frame)
function str.replace( frame )
local new_args = str._getParameters(frame.args, { 'source', 'pattern', 'replace', 'count', 'plain' });
local new_args = str._getParameters( frame.args, {'source', 'pattern', 'replace', 'count', 'plain' } )
local source_str = new_args['source'] or '';
local source_str = new_args['source'] or ''
local pattern = new_args['pattern'] or '';
local pattern = new_args['pattern'] or ''
local replace = new_args['replace'] or '';
local replace = new_args['replace'] or ''
local count = tonumber(new_args['count']);
local count = tonumber( new_args['count'] )
local plain = new_args['plain'] or true;
local plain = new_args['plain'] or true
 
if source_str == '' or pattern == '' then
if source_str == '' or pattern == '' then
return source_str;
return source_str
end
end
plain = str._getBoolean(plain);
plain = str._getBoolean( plain )
 
if plain then
if plain then
pattern = str.pattern_escape(pattern);
pattern = str._escapePattern( pattern )
replace = mw.ustring.gsub(replace, "%%", "%%%%"); --Only need to escape replacement sequences.
replace = string.gsub( replace, "%%", "%%%%" ) --Only need to escape replacement sequences.
end
end
 
local result;
local result
 
if count ~= nil then
if count ~= nil then
result = mw.ustring.gsub(source_str, pattern, replace, count);
result = mw.ustring.gsub( source_str, pattern, replace, count )
else
else
result = mw.ustring.gsub(source_str, pattern, replace);
result = mw.ustring.gsub( source_str, pattern, replace )
end
 
return result
end
 
--[[
    simple function to pipe string.rep to templates.
]]
function str.rep( frame )
local repetitions = tonumber( frame.args[2] )
if not repetitions then
return str._error( 'function rep expects a number as second parameter, received "' .. ( frame.args[2] or '' ) .. '"' )
end
end
return string.rep( frame.args[1] or '', repetitions )
return result;
end
end


--[[
escapePattern
This function escapes special characters from a Lua string pattern. See [1]
for details on how patterns work.


function str.gsub(frame)
[1] https://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Patterns
local params = {
 
[1] = { required = true, allow_empty = true },
Usage:
[2] = { required = true, allow_empty = true },
{{#invoke:String|escapePattern|pattern_string}}
[3] = { required = true, allow_empty = true },
 
[4] = { type = "number" },
Parameters
}
    pattern_string: The pattern string to escape.
]]
local args = require("Module:parameters").process(frame.args, params)
function str.escapePattern( frame )
local pattern_str = frame.args[1]
return (mw.ustring.gsub(args[1], args[2], args[3], args[4]))
if not pattern_str then
return str._error( 'No pattern string specified' )
end
local result = str._escapePattern( pattern_str )
return result
end
end


--[[
count
This function counts the number of occurrences of one string in another.
]]
function str.count(frame)
local args = str._getParameters(frame.args, {'source', 'pattern', 'plain'})
local source = args.source or ''
local pattern = args.pattern or ''
local plain = str._getBoolean(args.plain or true)
if plain then
pattern = str._escapePattern(pattern)
end
local _, count = mw.ustring.gsub(source, pattern, '')
return count
end


--[[
--[[
    simple function to pipe string.rep to templates.
endswith
This function determines whether a string ends with another string.
]]
]]
 
function str.endswith(frame)
function str.rep(frame)
local args = str._getParameters(frame.args, {'source', 'pattern'})
local repetitions = tonumber(frame.args[2])
local source = args.source or ''
if not repetitions then
local pattern = args.pattern or ''
return str._error('function rep expects a number as second parameter, received "' .. (frame.args[2] or '') .. '"')
if pattern == '' then
-- All strings end with the empty string.
return "yes"
end
if mw.ustring.sub(source, -mw.ustring.len(pattern), -1) == pattern then
return "yes"
else
return ""
end
end
return string.rep(frame.args[1] or '', repetitions)
end
end


function str.lower(frame)
--[[
local text = frame.args[1] or ''
join
return mw.ustring.lower(text)
 
Join all non empty arguments together; the first argument is the separator.
Usage:
{{#invoke:String|join|sep|one|two|three}}
]]
function str.join(frame)
local args = {}
local sep
for _, v in ipairs( frame.args ) do
if sep then
if v ~= '' then
table.insert(args, v)
end
else
sep = v
end
end
return table.concat( args, sep or '' )
end
end
str.lc = str.lower


--[[
--[[
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we sometimes want to either preserve or remove that whitespace depending on the application.
we sometimes want to either preserve or remove that whitespace depending on the application.
]]
]]
function str._getParameters(frame_args, arg_list)
function str._getParameters( frame_args, arg_list )
local new_args = {};
local new_args = {}
local index = 1;
local index = 1
local value;
local value
 
for _, arg in ipairs(arg_list) do
for _, arg in ipairs( arg_list ) do
value = frame_args[arg]
value = frame_args[arg]
if value == nil then
if value == nil then
value = frame_args[index];
value = frame_args[index]
index = index + 1;
index = index + 1
end
end
new_args[arg] = value;
new_args[arg] = value
end
end
 
return new_args;
return new_args
end
end


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Helper function to handle error messages.
Helper function to handle error messages.
]]
]]
function str._error(error_str)
function str._error( error_str )
local frame = mw.getCurrentFrame();
local frame = mw.getCurrentFrame()
local error_category = frame.args.error_category or 'Errors reported by Module String';
local error_category = frame.args.error_category or 'Errors reported by Module String'
local ignore_errors = frame.args.ignore_errors or false;
local ignore_errors = frame.args.ignore_errors or false
local no_category = frame.args.no_category or false;
local no_category = frame.args.no_category or false
 
if str._getBoolean(ignore_errors) then
if str._getBoolean(ignore_errors) then
return '';
return ''
end
end
 
local error_str = '<strong class="error">String Module Error: ' .. error_str .. '</strong>';
local error_str = '<strong class="error">String Module Error: ' .. error_str .. '</strong>'
if error_category ~= '' and not str._getBoolean(no_category) then
if error_category ~= '' and not str._getBoolean( no_category ) then
error_str = '[[Category:' .. error_category .. ']]' .. error_str;
error_str = '[[Category:' .. error_category .. ']]' .. error_str
end
end
 
return error_str;
return error_str
end
end


Line 452: Line 559:
Helper Function to interpret boolean strings
Helper Function to interpret boolean strings
]]
]]
function str._getBoolean(boolean_str)
function str._getBoolean( boolean_str )
local boolean_value;
local boolean_value
 
if type(boolean_str) == 'string' then
if type( boolean_str ) == 'string' then
boolean_str = boolean_str:lower();
boolean_str = boolean_str:lower()
if boolean_str == 'false' or boolean_str == 'no' or boolean_str == '0'
if boolean_str == 'false' or boolean_str == 'no' or boolean_str == '0'
or boolean_str == '' then
or boolean_str == '' then
boolean_value = false;
boolean_value = false
else
else
boolean_value = true;
boolean_value = true
end
end
elseif type(boolean_str) == 'boolean' then
elseif type( boolean_str ) == 'boolean' then
boolean_value = boolean_str;
boolean_value = boolean_str
else
else
error('No boolean value found');
error( 'No boolean value found' )
end
end
return boolean_value
return boolean_value
Line 472: Line 579:


--[[
--[[
Helper function that escapes all pattern characters – ().%+-*?[^$] – so that they will be treated
Helper function that escapes all pattern characters so that they will be treated
as plain text.
as plain text.
]]
]]
function str.pattern_escape(pattern_str)
function str._escapePattern( pattern_str )
local invoked = false
return ( string.gsub( pattern_str, "[%(%)%.%%%+%-%*%?%[%^%$%]]", "%%%0" ) )
if type(pattern_str) == "table" then
if pattern_str.args then
local frame = pattern_str
invoked = true
if frame.args[1] then
pattern_str = frame.args[1]
else
pattern_str = frame:getParent().args[1]
end
else
error("First argument to pattern_escape should be a string, a number, or a frame object.")
end
elseif not (type(pattern_str) == "string" or type(pattern_str) == "number") then
error("First argument to pattern_escape should be a string or a number.")
end
if invoked then
local escaped = mw.ustring.gsub(pattern_str, "([%(%)%.%%%+%-%*%?%[%^%$%]])", "%%%1")
return escaped
else
return mw.ustring.gsub(pattern_str, "([%(%)%.%%%+%-%*%?%[%^%$%]])", "%%%1");
end
end
 
function str.count(text, pattern, plain)
if not (type(text) == "string" or type(text) == "number") then
error('The first argument to the function "count" must be a string or a number, not a ' .. type(text) .. '.')
end
if not (type(pattern) == "string" or type(pattern) == "number") then
error('The first argument to the function "count" must be a string or a number, not a ' .. type(text) .. '.')
end
if plain then
pattern = str.pattern_escape(pattern)
end
local _, count = mw.ustring.gsub(text, pattern, "")
return count
end
 
function str.plain_gsub(text, pattern, replacement)
local invoked = false
if type(text) == "table" then
invoked = true
if text.args then
local frame = text
local params = {
[1] = {},
[2] = {},
[3] = { allow_empty = true },
}
local args = require("Module:parameters").process(frame.args, params)
text = args[1]
pattern = args[2]
replacement = args[3]
else
error("If the first argument to plain_gsub is a table, it should be a frame object.")
end
else
if not (type(pattern) == "string" or type(pattern) == "number") then
error("The second argument to plain_gsub should be a string or a number.")
end
if not (type(replacement) == "string" or type(replacement) == "number") then
error("The third argument to plain_gsub should be a string or a number.")
end
end
pattern = str.pattern_escape(pattern)
if invoked then
text = mw.ustring.gsub(text, pattern, replacement)
return text
else
return mw.ustring.gsub(text, pattern, replacement)
end
end
 
function str.matchToArray(text, pattern)
local invoked = false
if type(text) == "table" then
invoked = true
if text.args then
local frame = text
local params = {
[1] = { required = true },
[2] = { required = true },
}
local args = require("Module:parameters").process(frame.args, params)
text = args[1]
pattern = args[2]
else
error("If the first argument to plain_gsub is a table, it should be a frame object.")
end
else
if not (type(pattern) == "string" or type(pattern) == "number") then
error("The second argument to plain_gsub should be a string or a number.")
end
end
local matches = {}
local i = 0
for match in mw.ustring.gmatch(text, pattern) do
i = i + 1
matches[i] = match
end
if i > 0 then
if invoked then
return table.concat(matches, ", ")
else
return matches
end
else
if invoked then
return ""
else
return nil
end
end
end
 
--[=[
Similar to gmatch, but it returns the count of the match in addition to the
list of captures, something like ipairs().
If the pattern doesn't contain any captures, the whole match is returned.
Invoke thus:
for i, whole_match in require("Module:string").imatch(text, pattern) do
[ do something with i and whole_match ]
end
or
for i, capture1[, capture2[, capture3[, ...]]] in require("Module:string").imatch(text, pattern) do
[ do something with i and capture1 ]
end
For example, this code
for i, whole_match in require("Module:string").imatch("a b c", "[a-z]") do
mw.log(i, whole_match)
end
will log
1 a
2 b
3 c
]=]
function str.imatch(text, pattern, pos, plain, use_basic_Lua_function)
local i = 0
pos = pos or 0
if not string.find(pattern, "%b()") then
pattern = "(" .. pattern .. ")"
end
local find = use_basic_Lua_function and string.find or mw.ustring.find
return function()
i = i + 1
local return_values = { find(text, pattern, pos, plain) }
local j = return_values[2]
if return_values[3] then
pos = j + 1
-- Skip the first two returned values, which are the indices of the
-- whole match.
return i, unpack(return_values, 3)
end
end
end
 
function str.escapebytes(s)
return (string.gsub(s,
'.',
function(char)
return ('\\%03d'):format(string.byte(char))
end))
end
 
function str.URIdecode(frame)
return mw.uri.decode(frame.args[1], frame.args[2] or "PATH")
end
end


return str
return str

Latest revision as of 12:18, 9 October 2024

Module:String (edit | talk | history | links | watch | logs)

This module is intended to provide access to basic string functions.

Most of the functions provided here can be invoked with named parameters, unnamed parameters, or a mixture. If named parameters are used, Mediawiki will automatically remove any leading or trailing whitespace from the parameter. Depending on the intended use, it may be advantageous to either preserve or remove such whitespace.

Global options

ignore_errors
If set to 'true' or 1, any error condition will result in an empty string being returned rather than an error message.
error_category
If an error occurs, specifies the name of a category to include with the error message. The default category is Category:Errors reported by Module String (0).
no_category
If set to 'true' or 1, no category will be added if an error is generated.

Unit tests for this module are available at Module:String/testcases.

len

This function returns the length of the target string.

Usage:

{{#invoke:String|len|target_string}}

OR

{{#invoke:String|len|s= target_string }}

Parameters:

s
The string whose length to report

Examples:

  • {{#invoke:String|len| abcdefghi }} → 11
  • {{#invoke:String|len|s= abcdefghi }} → 9

sub

This function returns a substring of the target string at specified inclusive, one-indexed indices.

Usage:

{{#invoke:String|sub|target_string|start_index|end_index}}

OR

{{#invoke:String|sub|s= target_string |i= start_index |j= end_index }}

Parameters:

s
The string to return a subset of
i
The first index of the substring to return, defaults to 1.
j
The last index of the string to return, defaults to the last character.

The first character of the string is assigned an index of 1. If either i or j is a negative value, it is interpreted the same as selecting a character by counting from the end of the string. Hence, a value of -1 is the same as selecting the last character of the string.

If the requested indices are out of range for the given string, an error is reported. To avoid error messages, use {{#invoke:ustring|sub}} instead.

Examples:

  • "{{#invoke:String|sub| abcdefghi }}" → " abcdefghi "
  • "{{#invoke:String|sub|s= abcdefghi }}" → "abcdefghi"
  • "{{#invoke:String|sub| abcdefghi | 3 }}" → "bcdefghi "
  • "{{#invoke:String|sub|s= abcdefghi |i= 3 }}" → "cdefghi"
  • "{{#invoke:String|sub| abcdefghi | 3 | 4 }}" → "bc"
  • "{{#invoke:String|sub|s= abcdefghi |i= 3 |j= 4 }}" → "cd"

sublength

This function implements the features of {{str sub old}} and is kept in order to maintain these older templates. It returns a substring of the target string starting at a specified index and of a specified length.

Usage:

{{#invoke:String|sublength|s= target_string |i= start_index |len= length }}

Parameters:

s
The string
i
The starting index of the substring to return. The first character of the string is assigned an index of 0.
len
The length of the string to return, defaults to the last character.

Examples:

  • {{#invoke:String|sublength|s= abcdefghi }} → abcdefghi
  • {{#invoke:String|sublength|s= abcdefghi |i= 3 }} → defghi
  • {{#invoke:String|sublength|s= abcdefghi |i= 3 |len= 4 }} → defg

match

This function returns a substring from the source string that matches a specified pattern.

Usage:

{{#invoke:String|match|source_string|pattern_string|start_index|match_number|plain_flag|nomatch_output}}

OR

{{#invoke:String|match|s= source_string |pattern= pattern_string |start= start_index |match= match_number |plain= plain_flag |nomatch= nomatch_output }}

Parameters:

s
The string to search
pattern
The pattern or string to find within the string
start
The index within the source string to start the search. The first character of the string has index 1. Defaults to 1.
match
In some cases it may be possible to make multiple matches on a single string. This specifies which match to return, where the first match is match= 1. If a negative number is specified then a match is returned counting from the last match. Hence match = -1 is the same as requesting the last match. Defaults to 1.
plain
Boolean flag indicating that pattern should be understood as plain text and not as a Scribunto ustring pattern (a unicode-friendly Lua-style regular expression). Defaults to false (to change: plain=true)
nomatch
If no match is found, output the "nomatch" value rather than an error.
ignore_errors
If no match is found and ignore_errors=true, output an empty string rather than an error.

If the match_number or start_index are out of range for the string being queried, then this function generates an error. An error is also generated if no match is found. If one adds the parameter ignore_errors=true, then the error will be suppressed and an empty string will be returned on any failure.

For information on constructing Lua patterns, a form of regular expression, see:

Examples:

  • {{#invoke:String|match| abc123def456 |%d+}} → 123
  • {{#invoke:String|match|s= abc123def456 |pattern= %d+ }} → 123
  • {{#invoke:String|match| abc123def456 |%d+|6}} → 23
  • {{#invoke:String|match|s= abc123def456 |pattern= %d+ |start= 6 }} → 3
  • {{#invoke:String|match|s= abc123def456 |pattern= %d+ |start= 6 |match= 2 }} → 456
  • {{#invoke:String|match|s= abc123%d+ |pattern= %d+ }} → 123
  • {{#invoke:String|match|s= abc123%d+ |pattern= %d+ |plain= true }} → %d+
  • {{#invoke:String|match|s= abc |pattern= %d }} → String Module Error: Match not found
  • {{#invoke:String|match|s= abc |pattern= %d |nomatch= No numeric characters in string }} → No numeric characters in string
  • {{#invoke:String|match|s= abc |pattern= %d |ignore_errors= true }} →
  • {{#invoke:String|match|s= 0012001200 |pattern= 0*(%d*) }} → 12001200

pos

This function returns a single character from the target string at position pos.

Usage:

{{#invoke:String|pos|target_string|index_value}}

OR

{{#invoke:String|pos|target= target_string |pos= index_value }}

Parameters:

target
The string to search
pos
The index for the character to return

The first character has an index value of 1.

If one requests a negative value, this function will select a character by counting backwards from the end of the string. In other words pos = -1 is the same as asking for the last character.

A requested value of zero, or a value greater than the length of the string returns an error.

Examples:

  • {{#invoke:String|pos| abcdefghi | 4 }} → c
  • {{#invoke:String|pos|target= abcdefghi |pos= 4 }} → d

str_find

This function duplicates the behavior of {{str_find}}, including all of its quirks. This is provided in order to support existing templates, but is NOT RECOMMENDED for new code and templates. New code is recommended to use the "find" function instead.

Returns the first index in "source" that is a match to "target". Indexing is 1-based, and the function returns -1 if the "target" string is not present in "source".

Important Note: If the "target" string is empty / missing, this function returns a value of "1", which is generally unexpected behavior, and must be accounted for separately.

Usage:

{{#invoke:String|str_find|source_string|target_string}}

OR

{{#invoke:String|str_find|source= source_string |target= target_string }}

Parameters:

source
The string to search
target
The string to find within source

Examples:

  • {{#invoke:String|str_find| abc123def }} → 1
  • {{#invoke:String|str_find|source= abc123def }} → 1
  • {{#invoke:String|str_find| abc123def |123}} → 5
  • {{#invoke:String|str_find|source= abc123def |target= 123 }} → 4
  • {{#invoke:String|str_find| abc123def |not}} → -1

find

This function allows one to search for a target string or pattern within another string.

Usage:

{{#invoke:String|find|source_string|target_string|start_index|plain_flag}}

OR

{{#invoke:String|find|source= source_string |target= target_string |start= start_index |plain= plain_flag }}

Parameters:

source
The string to search
target
The string or pattern to find within source
start
The index within the source string to start the search, defaults to 1
plain
Boolean flag indicating that target should be understood as plain text and not as a Scribunto ustring pattern (a unicode-friendly Lua-style regular expression); defaults to true

This function returns the first index >= "start" where "target" can be found within "source". Indices are 1-based. If "target" is not found, then this function returns 0. If either "source" or "target" are missing / empty, this function also returns 0.

This function should be safe for UTF-8 strings.

Examples:

  • {{#invoke:String|find|abc123def|12}} → 4
  • {{#invoke:String|find|source=abc123def|target=12}} → 4
  • {{#invoke:String|find|source=abc123def|target=pqr}} → 0
  • {{#invoke:String|find| abc123def |123}} → 5
  • {{#invoke:String|find|source= abc123def |target= 123 }} → 4
  • {{#invoke:String|find|source=abc123def|target=%d |start=3 |plain=false }} → 4

When using unnamed parameters, preceding and trailing spaces are kept and counted:

  • {{#invoke:String|find| abc123def |c|false}} → 5
  • {{#invoke:String|find|source= abc123def |target=c|plain=false}} → 3
  • {{#invoke:string|find|abc 123 def|%s|plain=false}} → 4

Testing for the presence of a string:

  • {{#ifexpr:{{#invoke:string|find|haystack|needle}}|Found needle|Didn't find needle}} → Didn't find needle

replace (gsub)

This function allows one to replace a target string or pattern within another string. To Lua programmers: this function works internally by calling string.gsub.

Usage:

{{#invoke:String|replace|source_str|pattern_string|replace_string|replacement_count|plain_flag}}

OR

{{#invoke:String|replace|source= source_string |pattern= pattern_string |replace= replace_string |count= replacement_count |plain= plain_flag }}

Parameters:

source
The string to search
pattern
The string or pattern to find within source
replace
The replacement text
count
The number of occurrences to replace; defaults to all
plain
Boolean flag indicating that pattern should be understood as plain text and not as a Scribunto ustring pattern (a unicode-friendly Lua-style regular expression); defaults to true

Examples:

  • "{{#invoke:String|replace| abc123def456 |123|XYZ}}" → " abcXYZdef456 "
  • "{{#invoke:String|replace|source= abc123def456 |pattern= 123 |replace= XYZ }}" → "abcXYZdef456"
  • "{{#invoke:String|replace| abc123def456 |%d+|XYZ|1|false}}" → " abcXYZdef456 "
  • "{{#invoke:String|replace|source= abc123def456 |pattern= %d+ |replace= XYZ |count=1 |plain= false }}" → "abcXYZdef456"
  • "{{#invoke:String|replace|source= abc123def456 |pattern= %d+ |replace= XYZ |plain= false }}" → "abcXYZdefXYZ"
  • {{#invoke:String|replace|source= 0012001200 |pattern= ^0* |plain= false }} → 12001200

rep

Repeats a string n times. A simple function to pipe string.rep to templates.

Usage:

{{#invoke:String|rep|source|count}}

Parameters:

source
The string to repeat
count
The number of repetitions.

Examples:

  • "{{#invoke:String|rep|hello|3}}" → "hellohellohello"
  • "{{#invoke:String|rep| hello | 3 }}" → " hello hello hello "

escapePattern

In a Lua pattern, changes a class character into a literal character. For example: in a pattern, character . catches "any character"; escapePattern will convert it to %., catching just the literal character ".".

Usage:

  • {{#invoke:String|escapePattern|pattern_string}}

Parameters:

pattern_string
The pattern string to escape

Examples:

  • "{{#invoke:String|escapePattern|A.D.}}" → "A%.D%."
  • "{{#invoke:String|escapePattern|10%}}" → "10%%"

count

Counts the number of times a given pattern appears in the arguments that get passed on to this module. Counts disjoint matches only.

Usage:

{{#invoke:String|count|source_str|pattern_string|plain_flag}}

OR

{{#invoke:String|count|source= source_string |pattern= pattern_string|plain= plain_flag }}

Parameters:

source_string
The string to count occurrences in
pattern
The string or pattern to count occurrences of within source
plain
Boolean flag indicating that pattern should be understood as plain text and not as a Scribunto ustring pattern (a unicode-friendly Lua-style regular expression); defaults to true

Examples:

  • Count of 'a': "{{#invoke:String|count|aabbcc|a}}" → "2"
  • Count occurrences of 'aba': "{{#invoke:String|count|ababababab|aba}}" → "2"
  • Count of "either 'a' or 'c' ":"{{#invoke:String|count|aabbcc|[ac]|plain=false}}" → "4"
  • Count of "not 'a' ": "{{#invoke:String|count|aaabaaac|[^a]|plain=false}}" → "2"
  • Count of "starts with 'a' ": "{{#invoke:String|count|aaabaaac|^a|plain=false}}" → "1"

join

Joins all strings passed as arguments into one string, treating the first argument as a separator

Usage:

{{#invoke:String|join|separator|string1|string2|...}}

Parameters:

separator
String that separates each string being joined together
Note that leading and trailing spaces are not stripped from the separator.
string1/string2/...
Strings being joined together

Examples:

  • "{{#invoke:String|join|x|foo|bar|baz}}" → "fooxbarxbaz"
  • "{{#invoke:String|join||a|b|c|d|e|f|g}}" → "abcdefg"
  • "{{#invoke:String|join|,|a|b|c|d|e|f|g}}" → "a,b,c,d,e,f,g"
  • "{{#invoke:String|join|, |a|b|c|d|e|f|g}}" → "a, b, c, d, e, f, g"
  • "{{#invoke:String|join| – |a|b|c|d|e|f|g}}" → "a – b – c – d – e – f – g"

The preceding example uses the html entity &ndash; but the unicode character also works.

endswith

For the startswith function, see Module:String2 § startswith.

Usage:

{{#invoke:String|endswith|source_str|search_string}}

OR

{{#invoke:String|endswith|source= source_string |pattern= search_string}}

Returns "yes" if the source string ends with the search string. Use named parameters to have the strings trimmed before use. Despite the parameter name, search_string is not a Lua pattern, it is interpreted literally.

  • "{{#invoke:String|endswith|xxxyyy|y}}" → "yes"
  • "{{#invoke:String|endswith|xxxyyy|z}}" → ""

See also

--[[

This module is intended to provide access to basic string functions.

Most of the functions provided here can be invoked with named parameters,
unnamed parameters, or a mixture.  If named parameters are used, Mediawiki will
automatically remove any leading or trailing whitespace from the parameter.
Depending on the intended use, it may be advantageous to either preserve or
remove such whitespace.

Global options
    ignore_errors: If set to 'true' or 1, any error condition will result in
        an empty string being returned rather than an error message.

    error_category: If an error occurs, specifies the name of a category to
        include with the error message.  The default category is
        [Category:Errors reported by Module String].

    no_category: If set to 'true' or 1, no category will be added if an error
        is generated.

Unit tests for this module are available at Module:String/tests.
]]

local str = {}

--[[
len

This function returns the length of the target string.

Usage:
{{#invoke:String|len|target_string|}}
OR
{{#invoke:String|len|s=target_string}}

Parameters
    s: The string whose length to report

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the target string.
]]
function str.len( frame )
	local new_args = str._getParameters( frame.args, {'s'} )
	local s = new_args['s'] or ''
	return mw.ustring.len( s )
end

--[[
sub

This function returns a substring of the target string at specified indices.

Usage:
{{#invoke:String|sub|target_string|start_index|end_index}}
OR
{{#invoke:String|sub|s=target_string|i=start_index|j=end_index}}

Parameters
    s: The string to return a subset of
    i: The first index of the substring to return, defaults to 1.
    j: The last index of the string to return, defaults to the last character.

The first character of the string is assigned an index of 1.  If either i or j
is a negative value, it is interpreted the same as selecting a character by
counting from the end of the string.  Hence, a value of -1 is the same as
selecting the last character of the string.

If the requested indices are out of range for the given string, an error is
reported.
]]
function str.sub( frame )
	local new_args = str._getParameters( frame.args, { 's', 'i', 'j' } )
	local s = new_args['s'] or ''
	local i = tonumber( new_args['i'] ) or 1
	local j = tonumber( new_args['j'] ) or -1

	local len = mw.ustring.len( s )

	-- Convert negatives for range checking
	if i < 0 then
		i = len + i + 1
	end
	if j < 0 then
		j = len + j + 1
	end

	if i > len or j > len or i < 1 or j < 1 then
		return str._error( 'String subset index out of range' )
	end
	if j < i then
		return str._error( 'String subset indices out of order' )
	end

	return mw.ustring.sub( s, i, j )
end

--[[
This function implements that features of {{str sub old}} and is kept in order
to maintain these older templates.
]]
function str.sublength( frame )
	local i = tonumber( frame.args.i ) or 0
	local len = tonumber( frame.args.len )
	return mw.ustring.sub( frame.args.s, i + 1, len and ( i + len ) )
end

--[[
_match

This function returns a substring from the source string that matches a
specified pattern. It is exported for use in other modules

Usage:
strmatch = require("Module:String")._match
sresult = strmatch( s, pattern, start, match, plain, nomatch )

Parameters
    s: The string to search
    pattern: The pattern or string to find within the string
    start: The index within the source string to start the search.  The first
        character of the string has index 1.  Defaults to 1.
    match: In some cases it may be possible to make multiple matches on a single
        string.  This specifies which match to return, where the first match is
        match= 1.  If a negative number is specified then a match is returned
        counting from the last match.  Hence match = -1 is the same as requesting
        the last match.  Defaults to 1.
    plain: A flag indicating that the pattern should be understood as plain
        text.  Defaults to false.
    nomatch: If no match is found, output the "nomatch" value rather than an error.

For information on constructing Lua patterns, a form of [regular expression], see:

* http://www.lua.org/manual/5.1/manual.html#5.4.1
* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Patterns
* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Ustring_patterns

]]
-- This sub-routine is exported for use in other modules
function str._match( s, pattern, start, match_index, plain_flag, nomatch )
	if s == '' then
		return str._error( 'Target string is empty' )
	end
	if pattern == '' then
		return str._error( 'Pattern string is empty' )
	end
	start = tonumber(start) or 1
	if math.abs(start) < 1 or math.abs(start) > mw.ustring.len( s ) then
		return str._error( 'Requested start is out of range' )
	end
	if match_index == 0 then
		return str._error( 'Match index is out of range' )
	end
	if plain_flag then
		pattern = str._escapePattern( pattern )
	end

	local result
	if match_index == 1 then
		-- Find first match is simple case
		result = mw.ustring.match( s, pattern, start )
	else
		if start > 1 then
			s = mw.ustring.sub( s, start )
		end

		local iterator = mw.ustring.gmatch(s, pattern)
		if match_index > 0 then
			-- Forward search
			for w in iterator do
				match_index = match_index - 1
				if match_index == 0 then
					result = w
					break
				end
			end
		else
			-- Reverse search
			local result_table = {}
			local count = 1
			for w in iterator do
				result_table[count] = w
				count = count + 1
			end

			result = result_table[ count + match_index ]
		end
	end

	if result == nil then
		if nomatch == nil then
			return str._error( 'Match not found' )
		else
			return nomatch
		end
	else
		return result
	end
end

--[[
match

This function returns a substring from the source string that matches a
specified pattern.

Usage:
{{#invoke:String|match|source_string|pattern_string|start_index|match_number|plain_flag|nomatch_output}}
OR
{{#invoke:String|match|s=source_string|pattern=pattern_string|start=start_index
    |match=match_number|plain=plain_flag|nomatch=nomatch_output}}

Parameters
    s: The string to search
    pattern: The pattern or string to find within the string
    start: The index within the source string to start the search.  The first
        character of the string has index 1.  Defaults to 1.
    match: In some cases it may be possible to make multiple matches on a single
        string.  This specifies which match to return, where the first match is
        match= 1.  If a negative number is specified then a match is returned
        counting from the last match.  Hence match = -1 is the same as requesting
        the last match.  Defaults to 1.
    plain: A flag indicating that the pattern should be understood as plain
        text.  Defaults to false.
    nomatch: If no match is found, output the "nomatch" value rather than an error.

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from each string.  In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.

If the match_number or start_index are out of range for the string being queried, then
this function generates an error.  An error is also generated if no match is found.
If one adds the parameter ignore_errors=true, then the error will be suppressed and
an empty string will be returned on any failure.

For information on constructing Lua patterns, a form of [regular expression], see:

* http://www.lua.org/manual/5.1/manual.html#5.4.1
* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Patterns
* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Ustring_patterns

]]
-- This is the entry point for #invoke:String|match
function str.match( frame )
	local new_args = str._getParameters( frame.args, {'s', 'pattern', 'start', 'match', 'plain', 'nomatch'} )
	local s = new_args['s'] or ''
	local start = tonumber( new_args['start'] ) or 1
	local plain_flag = str._getBoolean( new_args['plain'] or false )
	local pattern = new_args['pattern'] or ''
	local match_index = math.floor( tonumber(new_args['match']) or 1 )
	local nomatch = new_args['nomatch']

	return str._match( s, pattern, start, match_index, plain_flag, nomatch )
end

--[[
pos

This function returns a single character from the target string at position pos.

Usage:
{{#invoke:String|pos|target_string|index_value}}
OR
{{#invoke:String|pos|target=target_string|pos=index_value}}

Parameters
    target: The string to search
    pos: The index for the character to return

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the target string.  In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.

The first character has an index value of 1.

If one requests a negative value, this function will select a character by counting backwards
from the end of the string.  In other words pos = -1 is the same as asking for the last character.

A requested value of zero, or a value greater than the length of the string returns an error.
]]
function str.pos( frame )
	local new_args = str._getParameters( frame.args, {'target', 'pos'} )
	local target_str = new_args['target'] or ''
	local pos = tonumber( new_args['pos'] ) or 0

	if pos == 0 or math.abs(pos) > mw.ustring.len( target_str ) then
		return str._error( 'String index out of range' )
	end

	return mw.ustring.sub( target_str, pos, pos )
end

--[[
str_find

This function duplicates the behavior of {{str_find}}, including all of its quirks.
This is provided in order to support existing templates, but is NOT RECOMMENDED for
new code and templates.  New code is recommended to use the "find" function instead.

Returns the first index in "source" that is a match to "target".  Indexing is 1-based,
and the function returns -1 if the "target" string is not present in "source".

Important Note: If the "target" string is empty / missing, this function returns a
value of "1", which is generally unexpected behavior, and must be accounted for
separatetly.
]]
function str.str_find( frame )
	local new_args = str._getParameters( frame.args, {'source', 'target'} )
	local source_str = new_args['source'] or ''
	local target_str = new_args['target'] or ''

	if target_str == '' then
		return 1
	end

	local start = mw.ustring.find( source_str, target_str, 1, true )
	if start == nil then
		start = -1
	end

	return start
end

--[[
find

This function allows one to search for a target string or pattern within another
string.

Usage:
{{#invoke:String|find|source_str|target_string|start_index|plain_flag}}
OR
{{#invoke:String|find|source=source_str|target=target_str|start=start_index|plain=plain_flag}}

Parameters
    source: The string to search
    target: The string or pattern to find within source
    start: The index within the source string to start the search, defaults to 1
    plain: Boolean flag indicating that target should be understood as plain
        text and not as a Lua style regular expression, defaults to true

If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the parameter.  In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.

This function returns the first index >= "start" where "target" can be found
within "source".  Indices are 1-based.  If "target" is not found, then this
function returns 0.  If either "source" or "target" are missing / empty, this
function also returns 0.

This function should be safe for UTF-8 strings.
]]
function str.find( frame )
	local new_args = str._getParameters( frame.args, {'source', 'target', 'start', 'plain' } )
	local source_str = new_args['source'] or ''
	local pattern = new_args['target'] or ''
	local start_pos = tonumber(new_args['start']) or 1
	local plain = new_args['plain'] or true

	if source_str == '' or pattern == '' then
		return 0
	end

	plain = str._getBoolean( plain )

	local start = mw.ustring.find( source_str, pattern, start_pos, plain )
	if start == nil then
		start = 0
	end

	return start
end

--[[
replace

This function allows one to replace a target string or pattern within another
string.

Usage:
{{#invoke:String|replace|source_str|pattern_string|replace_string|replacement_count|plain_flag}}
OR
{{#invoke:String|replace|source=source_string|pattern=pattern_string|replace=replace_string|
   count=replacement_count|plain=plain_flag}}

Parameters
    source: The string to search
    pattern: The string or pattern to find within source
    replace: The replacement text
    count: The number of occurences to replace, defaults to all.
    plain: Boolean flag indicating that pattern should be understood as plain
        text and not as a Lua style regular expression, defaults to true
]]
function str.replace( frame )
	local new_args = str._getParameters( frame.args, {'source', 'pattern', 'replace', 'count', 'plain' } )
	local source_str = new_args['source'] or ''
	local pattern = new_args['pattern'] or ''
	local replace = new_args['replace'] or ''
	local count = tonumber( new_args['count'] )
	local plain = new_args['plain'] or true

	if source_str == '' or pattern == '' then
		return source_str
	end
	plain = str._getBoolean( plain )

	if plain then
		pattern = str._escapePattern( pattern )
		replace = string.gsub( replace, "%%", "%%%%" ) --Only need to escape replacement sequences.
	end

	local result

	if count ~= nil then
		result = mw.ustring.gsub( source_str, pattern, replace, count )
	else
		result = mw.ustring.gsub( source_str, pattern, replace )
	end

	return result
end

--[[
    simple function to pipe string.rep to templates.
]]
function str.rep( frame )
	local repetitions = tonumber( frame.args[2] )
	if not repetitions then
		return str._error( 'function rep expects a number as second parameter, received "' .. ( frame.args[2] or '' ) .. '"' )
	end
	return string.rep( frame.args[1] or '', repetitions )
end

--[[
escapePattern

This function escapes special characters from a Lua string pattern. See [1]
for details on how patterns work.

[1] https://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Patterns

Usage:
{{#invoke:String|escapePattern|pattern_string}}

Parameters
    pattern_string: The pattern string to escape.
]]
function str.escapePattern( frame )
	local pattern_str = frame.args[1]
	if not pattern_str then
		return str._error( 'No pattern string specified' )
	end
	local result = str._escapePattern( pattern_str )
	return result
end

--[[
count
This function counts the number of occurrences of one string in another.
]]
function str.count(frame)
	local args = str._getParameters(frame.args, {'source', 'pattern', 'plain'})
	local source = args.source or ''
	local pattern = args.pattern or ''
	local plain = str._getBoolean(args.plain or true)
	if plain then
		pattern = str._escapePattern(pattern)
	end
	local _, count = mw.ustring.gsub(source, pattern, '')
	return count
end

--[[
endswith
This function determines whether a string ends with another string.
]]
function str.endswith(frame)
	local args = str._getParameters(frame.args, {'source', 'pattern'})
	local source = args.source or ''
	local pattern = args.pattern or ''
	if pattern == '' then
		-- All strings end with the empty string.
		return "yes"
	end
	if mw.ustring.sub(source, -mw.ustring.len(pattern), -1) == pattern then
		return "yes"
	else
		return ""
	end
end

--[[
join

Join all non empty arguments together; the first argument is the separator.
Usage:
{{#invoke:String|join|sep|one|two|three}}
]]
function str.join(frame)
	local args = {}
	local sep
	for _, v in ipairs( frame.args ) do
		if sep then
			if v ~= '' then
				table.insert(args, v)
			end
		else
			sep = v
		end
	end
	return table.concat( args, sep or '' )
end

--[[
Helper function that populates the argument list given that user may need to use a mix of
named and unnamed parameters.  This is relevant because named parameters are not
identical to unnamed parameters due to string trimming, and when dealing with strings
we sometimes want to either preserve or remove that whitespace depending on the application.
]]
function str._getParameters( frame_args, arg_list )
	local new_args = {}
	local index = 1
	local value

	for _, arg in ipairs( arg_list ) do
		value = frame_args[arg]
		if value == nil then
			value = frame_args[index]
			index = index + 1
		end
		new_args[arg] = value
	end

	return new_args
end

--[[
Helper function to handle error messages.
]]
function str._error( error_str )
	local frame = mw.getCurrentFrame()
	local error_category = frame.args.error_category or 'Errors reported by Module String'
	local ignore_errors = frame.args.ignore_errors or false
	local no_category = frame.args.no_category or false

	if str._getBoolean(ignore_errors) then
		return ''
	end

	local error_str = '<strong class="error">String Module Error: ' .. error_str .. '</strong>'
	if error_category ~= '' and not str._getBoolean( no_category ) then
		error_str = '[[Category:' .. error_category .. ']]' .. error_str
	end

	return error_str
end

--[[
Helper Function to interpret boolean strings
]]
function str._getBoolean( boolean_str )
	local boolean_value

	if type( boolean_str ) == 'string' then
		boolean_str = boolean_str:lower()
		if boolean_str == 'false' or boolean_str == 'no' or boolean_str == '0'
				or boolean_str == '' then
			boolean_value = false
		else
			boolean_value = true
		end
	elseif type( boolean_str ) == 'boolean' then
		boolean_value = boolean_str
	else
		error( 'No boolean value found' )
	end
	return boolean_value
end

--[[
Helper function that escapes all pattern characters so that they will be treated
as plain text.
]]
function str._escapePattern( pattern_str )
	return ( string.gsub( pattern_str, "[%(%)%.%%%+%-%*%?%[%^%$%]]", "%%%0" ) )
end

return str
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