Module:String: Difference between revisions

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en>Mr. Stradivarius
(Add "rep" function per request by User:קיפודנחש at Wikipedia:Lua requests#Template:Loop and Template:Loop15. Copied from sandbox.)
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--[[
--[[


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


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


Global options
Global options
     ignore_errors: If set to 'true' or 1, any error condition will result in  
     ignore_errors: If set to 'true' or 1, any error condition will result in
         an empty string being returned rather than an error message.
         an empty string being returned rather than an error message.
       
 
     error_category: If an error occurs, specifies the name of a category to  
     error_category: If an error occurs, specifies the name of a category to
         include with the error message.  The default category is
         include with the error message.  The default category is
         [Category:Errors reported by Module String].
         [Category:Errors reported by Module String].
       
 
     no_category: If set to 'true' or 1, no category will be added if an error
     no_category: If set to 'true' or 1, no category will be added if an error
         is generated.
         is generated.
       
 
Unit tests for this module are available at Module:String/tests.
Unit tests for this module are available at Module:String/tests.
]]
]]
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If invoked using named parameters, Mediawiki will automatically remove any leading or
If invoked using named parameters, Mediawiki will automatically remove any leading or
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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     i: The fist index of the substring to return, defaults to 1.
     i: The fist 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
counting from the end of the string.  Hence, a value of -1 is the same as  
counting from the end of the string.  Hence, a value of -1 is the same as
selecting the last character of the string.
selecting the last character of the string.


If the requested indices are out of range for the given string, an error is  
If the requested indices are out of range for the given string, an error is
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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--[[
--[[
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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     start: The index within the source string to start the search.  The first
     start: The index within the source string to start the search.  The first
         character of the string has index 1.  Defaults to 1.
         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  
     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  
         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  
         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
         counting from the last match.  Hence match = -1 is the same as requesting
         the last match.  Defaults to 1.
         the last match.  Defaults to 1.
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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
    start = tonumber(start) or 1
     if math.abs(start) < 1 or math.abs(start) > mw.ustring.len( s ) then
     if math.abs(start) < 1 or math.abs(start) > mw.ustring.len( s ) then
         return str._error( 'Requested start is out of range' );
         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._escapePattern( pattern );
         pattern = str._escapePattern( pattern )
     end
     end
   
 
     local result
     local result
     if match_index == 1 then
     if match_index == 1 then
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     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


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


The first character has an index value of 1.
The first character has an index value of 1.


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


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]]
]]
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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This function duplicates the behavior of {{str_find}}, including all of its quirks.
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  
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.
new code and templates.  New code is recommended to use the "find" function instead.


Line 268: Line 306:
]]
]]
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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If invoked using named parameters, Mediawiki will automatically remove any leading or
If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the parameter.  In some circumstances this is desirable, in  
trailing whitespace from the parameter.  In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.
other cases one may want to preserve the whitespace.


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 0.  If either "source" or "target" are missing / empty, this
function returns 0.  If either "source" or "target" are missing / empty, this
function also returns 0.
function also returns 0.
Line 314: Line 352:
]]
]]
function str.find( frame )
function str.find( frame )
     local new_args = str._getParameters( frame.args, {'source', 'target', 'start', 'plain' } );
     local new_args = str._getParameters( frame.args, {'source', 'target', 'start', 'plain' } )
     local source_str = new_args['source'] or '';
     local source_str = new_args['source'] or ''
     local pattern = new_args['target'] or '';
     local pattern = new_args['target'] or ''
     local start_pos = tonumber(new_args['start']) or 1;
     local start_pos = tonumber(new_args['start']) or 1
     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 0;
         return 0
     end  
     end
   
 
     plain = str._getBoolean( plain );
     plain = str._getBoolean( plain )


     local start = mw.ustring.find( source_str, pattern, start_pos, plain )
     local start = mw.ustring.find( source_str, pattern, start_pos, plain )
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         start = 0
         start = 0
     end
     end
   
 
     return start
     return start
end
end
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     count: The number of occurences to replace, defaults to all.
     count: The number of occurences to replace, defaults to all.
     plain: Boolean flag indicating that pattern should be understood as plain
     plain: Boolean flag indicating that pattern should be understood as plain
         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._escapePattern( pattern );
         pattern = str._escapePattern( pattern )
         replace = mw.ustring.gsub( replace, "%%", "%%%%" ); --Only need to escape replacement sequences.
         replace = mw.ustring.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      
     end


     return result;
     return result
end
end


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


Line 402: Line 519:
]]
]]
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 i,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


--[[
--[[
Line 422: Line 539:
]]
]]
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 443: Line 560:
]]
]]
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
end
end


--[[
--[[
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._escapePattern( pattern_str )
function str._escapePattern( pattern_str )
     return mw.ustring.gsub( pattern_str, "([%(%)%.%%%+%-%*%?%[%^%$%]])", "%%%1" );
     return mw.ustring.gsub( pattern_str, "([%(%)%.%%%+%-%*%?%[%^%$%]])", "%%%1" )
end
end


return str
return str

Latest revision as of 18:47, 23 September 2024

Module documentation[create] [purge]
--[[

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 fist 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 = mw.ustring.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 mw.ustring.gsub( pattern_str, "([%(%)%.%%%+%-%*%?%[%^%$%]])", "%%%1" )
end

return str