A module for detecting updated files in a LÖVE game

hotreload.lua

-- Detecting updated files for hot reloading in a LÖVE game
local hotreload = {}

-- Monitor the "src" and "assets" paths, can be changed to any existing folders in your project, separated by spaces
local monitor_path = "src assets"
-- External command for monitoring the filesystem
-- Needs fswatch available for execution in PATH (no errors will be thrown, but reload will not work)
-- https://github.com/emcrisostomo/fswatch
local fswatch_cmd = "fswatch --recursive --event Updated " .. monitor_path

function hotreload.load()
    hotreload.channel = love.thread.newChannel()
    
    -- This may be used to retrieve the relative file paths from fswatch's output
    hotreload.source = love.filesystem.getSource()

    -- Reading a subprocess output is a blocking operation, so it must run in a separate thread
    local thread = love.thread.newThread([[
    local channel, fswatch_cmd = ...
    local fswatch = io.popen(fswatch_cmd)
    -- `io.popen` returns an open file even if the command failed
    -- This `if` is not mandatory, but this will make the thread finish instead of being blocked forever for nothing
    if fswatch:read(0) then
        for line in fswatch:lines() do
            channel:push(line)
        end
    else
        print(string.format('HOTRELOAD failed running %q and is disabled', fswatch_cmd))
    end
    ]])
    thread:start(hotreload.channel, fswatch_cmd)
end

function hotreload.update()
    -- Note: if no files are updated or if the fswatch command failed, nothing happens =]
    while hotreload.channel:getCount() > 0 do
        local filename = hotreload.channel:pop()
        -- Note: fswatch returns full file paths.
        -- You can get the relative path by trimming the project source path with the following line
        -- `+2` is for skipping the trailing "/" or "\"
        filename = filename:sub(#hotreload.source + 2)
        print('UPDATED', filename)
        
        -- Example: reload image assets into global table
        local imagename = filename:match("([^/\\]+)%.png$")
        if imagename then
            print(string.format('Reloading image %q into global table', imagename))
            _G[imagename] = love.graphics.newImage(filename)
        end
    end
end

return hotreload

usage.lua

local hotreload = require 'hotreload'

function love.load()
    -- do your usual loading here
    hotreload.load()
end

function love.update(dt)
    -- hotreloading stuff in the beginning of the update means the new stuff is readily available in your update cycle
    hotreload.update()
    -- your usual update here
end

function love.draw()
    -- your usual draw here, no drawing is needed for hotreload
end