Lazy _s (underscores) theme generation with Lua. Tested in Windows only. Needs the `_s` dist folder in the same directory as build.lua

build.lua

-- Written by Phoenix Enero. MIT License. Sorry for bad english

-- Global Config
local os = 'windows' -- 'unix'
local settings = {
    -- note: must be contained in single quotes
    text_domain       = "'megatherium'",
    function_names    =  'megatherium_',
    text_domain_style =  'Text Domain: megatherium',
    docblocks         =  ' Megatherium',
    handles           =  'megatherium-'
}

-- Requires
local gsub = string.gsub

-- Other
local _log = ''

-------------
-- HELPERS --
-------------

-- Log files
function log(str, doprint)
    _log = _log .. str .. '\n'
    
    if doprint then
        print(str)
    end
end

-- Lua implementation of PHP scandir function
function scandir(directory)
    local i, t, popen, cmd = 0, {}, io.popen, ''
    
    if os == 'windows' then
        cmd = 'dir "' .. directory .. '" /s /b'
    else
        cmd = 'ls -aR "' .. directory .. '"'
    end
    
    -- Loop through files and populate table
    for filename in popen( cmd ):lines() do
        i = i + 1
        t[i] = filename
        log(filename)
    end

    -- Return table of filenames    
    return t
end

-- Literalize strings for string.gsub
-- https://stackoverflow.com/questions/1745448/lua-plain-string-gsub
function literalize(str)
    return str:gsub("[%(%)%.%%%+%-%*%?%[%]%^%$]", function(c) return "%" .. c end)
end

-------------
--/HELPERS --
-------------

print('\n\n##############################################')
print('\nCurrently building an Underscores distribution\n')
print('##############################################\n\n')

-- Literalize settings
log('Escaping problematic characters\n', true)
for _, str in pairs( settings ) do
    str = literalize(str)
    log('escaped: ' .. str)
end

-- Find relevant files
local filenames = {}

log('\nBuilding file list\n', true)
local all_files = scandir('_s')

log('\nFiltering files\n', true)
for i, file in pairs(all_files) do
    if string.find( file, '%.php' ) or
       string.find( file, '%.css' ) then
       filenames[i] = file
       log(file)
    end
end
    
-- Automagically find and replace all relevant files
print('\nFinding and replacing all patterns for _s')
for _, fn in pairs( filenames ) do
    fp = io.open( fn, 'r' )
    str = fp:read( '*all' )
    print('Reading ' .. fn)
    
    -- Capture text domain
    str = gsub( str, "'_s'", settings.text_domain )
    
    -- Capture function names
    str = gsub( str, '_s_', settings.function_names )
    
    -- Capture style.css text domain
    str = gsub( str, 'Text Domain: _s', settings.text_domain_style )
    
    -- Capture DocBlocks
    str = gsub( str, ' _s', settings.docblocks )
    
    -- Capture prefixed handles
    str = gsub( str, '_s%-', settings.handles )
    
    fp:close()
 
    fp = io.open( fn, 'w+' )
    print('Writing to ' .. fn)
    fp:write( str )
    fp:close()
end

print('\n\n##############################################')
print('\nDone!\n')
print('##############################################\n\n')

-- Finish logging
debug_log = io.open( 'debug.log', 'w+' )
print('\nLogging info to debug.log')
debug_log:write( _log )
debug_log:close()