Phoenix Live Reload default setup leaves out some code files, Why?

The live reload config you see here is about which files should, immediately on save, automatically trigger the page itself to reload.

It’s the code_reloader that handles recompiling your core Elixir code on page refresh. I ran a new copy of phoenix and saw the following in endpoint.ex:

  # Code reloading can be explicitly enabled under the
  # :code_reloader configuration of your endpoint.
  if code_reloading? do
    socket "/phoenix/live_reload/socket", Phoenix.LiveReloader.Socket
    plug Phoenix.LiveReloader
    plug Phoenix.CodeReloader
  end

And when I checked dev.exs I see:

config :my_app_web, MyAppWeb.Endpoint,
  http: [port: 4000],
  debug_errors: true,
  code_reloader: true,
  check_origin: false,
  watchers: [
    node: [
      "node_modules/webpack/bin/webpack.js",
      "--mode",
      "development",
      "--watch-stdin",
      cd: Path.expand("../apps/my_app_web/assets", __DIR__)
    ]
  ]

Importantly code_reloader: true. Does this line up with what you see in your project?

One potential issue here is what happens if you have a GenServer that assumes state in a certain format, then you change it, it reloads the code, and the old genserver state is now erroneous.

This is just speculation on my part, but I’m assuming that this is why the default is the way it is. The files that Phoenix owns are known to be safe, but your application cannot be known to be safe. Beginners may get even more confused by not knowing why things are broken.

Code reloader is enabled:

config :tasks, TasksWeb.Endpoint,
  http: [port: 4000],
  debug_errors: true,
  code_reloader: true,
  check_origin: false,
  watchers: [
    node: [
      "node_modules/webpack/bin/webpack.js",
      "--mode",
      "development",
      "--watch-stdin",
      cd: Path.expand("../assets", __DIR__)
    ]
  ]

Thanks for the explanation, but I see this issue across a lot of pet projects I play with, but I will try later in neu project and see if I can spot any difference.

No using one, at least directly, plus this issue with code not reloading is across several projects.

This is what I am trying to understand, If the defaults are just playing on the safe side as you say or it’s something wrong in my setup.

Is there anything unusual about your development environment? Are you running stuff inside docker?

Yes I am, and the container have inotify tools installed and the limit increased.

Which OS?

OS

Host:

$ cat /etc/os-release 
NAME="Ubuntu"
VERSION="18.04.4 LTS (Bionic Beaver)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 18.04.4 LTS"
VERSION_ID="18.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=bionic
UBUNTU_CODENAME=bionic

Container:

$ cat /etc/os-release                                                                                                                
PRETTY_NAME="Debian GNU/Linux 9 (stretch)"
NAME="Debian GNU/Linux"
VERSION_ID="9"
VERSION="9 (stretch)"
VERSION_CODENAME=stretch
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

Inotify

Host

$ cat /etc/sysctl.conf | grep inotify - 
fs.inotify.max_user_watches=524288

Container

Seems this container is after all missing the increase in the inotify watchers… Seems that at some point in time I may have removed it accidentally from the base image.

I will fix this and see if it solves the issue.