os.loadAPI

-- https://github.com/cc-tweaked/CC-Tweaked/blob/f4e542b4db686dad6f3fe1c4fe0006fc06dd2bd9/src/main/resources/data/computercraft/lua/bios.lua#L6-L15
local expect

do
    local h = fs.open("rom/modules/main/cc/expect.lua", "r")
    local f, err = loadstring(h.readAll(), "@expect.lua")
    h.close()

    if not f then error(err) end
    expect = f().expect
end

-- https://github.com/cc-tweaked/CC-Tweaked/blob/f4e542b4db686dad6f3fe1c4fe0006fc06dd2bd9/src/main/resources/data/computercraft/lua/bios.lua#L520-L564
local tAPIsLoading = {}
function os.loadAPI(_sPath)
    expect(1, _sPath, "string")
    local sName = fs.getName(_sPath)
    if sName:sub(-4) == ".lua" then
        sName = sName:sub(1, -5)
    end
    if tAPIsLoading[sName] == true then
        printError("API " .. sName .. " is already being loaded")
        return false
    end
    tAPIsLoading[sName] = true

    local tEnv = {}
    setmetatable(tEnv, { __index = _G })
    local fnAPI, err = loadfile(_sPath, nil, tEnv)
    if fnAPI then
        local ok, err = pcall(fnAPI)
        if not ok then
            tAPIsLoading[sName] = nil
            return error("Failed to load API " .. sName .. " due to " .. err, 1)
        end
    else
        tAPIsLoading[sName] = nil
        return error("Failed to load API " .. sName .. " due to " .. err, 1)
    end

    local tAPI = {}
    for k, v in pairs(tEnv) do
        if k ~= "_ENV" then
            tAPI[k] =  v
        end
    end

    _G[sName] = tAPI
    tAPIsLoading[sName] = nil
    return true
end

function os.unloadAPI(_sName)
    expect(1, _sName, "string")
    if _sName ~= "_G" and type(_G[_sName]) == "table" then
        _G[_sName] = nil
    end
end