Simple test to show correctness of file extension matching patterns in lua

file_ext_match.lua

local filenames = {
    ["filename"] = "nil",
    [".filename"] = "nil",
    ["filename."] = "nil",
    [".filename."] = "nil",
    ["filename.ext"] = "ext",
    [".filename.ext"] = "ext",
    ["filename.ext."] = "nil",
    ["file.name.ext"] = "ext",
    [".file.name.ext"] = "ext",
    ["file.name.ext."] = "nil",
    [".file.name.ext."] = "nil",
}

local patterns = {
    "%.(.*)$",      "%.(.-)$",      "%.(.+)$",
    ".*%.(.*)$",    ".*%.(.-)$",    ".*%.(.+)$",
    ".-%.(.*)$",    ".-%.(.-)$",    ".-%.(.+)$",
    ".+%.(.*)$",    ".+%.(.-)$",    ".+%.(.+)$",
    "%.([^.]*)$",   "%.([^.]-)$",   "%.([^.]+)$",
    ".*%.([^.]*)$", ".*%.([^.]-)$", ".*%.([^.]+)$",
    ".-%.([^.]*)$", ".-%.([^.]-)$", ".-%.([^.]+)$",
    ".+%.([^.]*)$", ".+%.([^.]-)$", ".+%.([^.]+)$",
    "[^.]+$",
}

local res = {}

for f,ext in pairs(filenames) do
    -- print() print(f, ext)
    for i,p in ipairs(patterns) do
        local m = string.match(f, p)
        local is_corr = tostring(m) == ext
        if not res[i] then res[i] = {} end
        if not is_corr then
            table.insert(res[i], f)
        end
        -- print(p.."  ", m)
    end
end

print() print("pattern", "  ", "fails at")
for i,fails in pairs(res) do
    table.sort(fails)
    print(patterns[i].."  ", table.unpack(fails))
end

print() print("correct patterns:")
for i,p in ipairs(patterns) do
    if #res[i] == 0 then
        print(p)
    end
end