Difference between revisions of "Module:String"

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--[[ 
 
  
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.
 
 
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:
 
 
* https://www.lua.org/manual/5.1/manual.html#5.4.1
 
* https://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Patterns
 
* https://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Ustring_patterns
 
 
]]
 
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'];
 
   
 
    if s == '' then
 
        return str._error( 'Target string is empty' );
 
    end
 
    if pattern == '' then
 
        return str._error( 'Pattern string is empty' );
 
    end
 
    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
 
 
--[[
 
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
 
 
--[[
 
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 i,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
 

Revision as of 23:25, 26 September 2018