Is there a way to use in umbrella children the same package with different configurations?

Questions / Help
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1

I know that some packages (like Pow) are designed to have their configuration per otp_app but unfortunately not all. For example I would like to use scrivener_html as stated here with different view style per umbrella web app, but don’t know how.

For packages like these (that don’t support configuration per otp_app), how one could manage to use them in umbrella children? Maybe a way to import them twice with different aliases?

2

No.

Only a single configuration is loaded, and if you have multiple config for a single application, they will get merged, and the new config statement will overwrite configuration values on conflict.

You’ll need to find a way to pass in config per call in those applications.

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3

Depending on how exactly the package in question fetches it’s configuration you’re out of luck. Some packages offer a init callback hook, others allow to specify configuration when adding their process to your supervision tree.

In the case of scrivener_html it seems you’re out of luck.

This is one of the disadvantages of using an umbrella application, configuration can get difficult. Since you need different configuration per application maybe this is a sign that you might want to reconsider having them in the same umbrella?

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4

Imho this is not at all related to umbrellas, but it’s a problem of library architecture. Even without an umbrella there might be a need to have different configuration to be used with a library. This is never supported when the only way to supply configuration is via the app env.

https://hexdocs.pm/elixir/library-guidelines.html#avoid-application-configuration

For scrivener_html this is not a problem though because you can supply config as a parameter:

# MyAppWeb.ex
def scrivener_config do
  Application.get_env(:my_app, :scrivener_html, [])
end

# In a view
import Scrivener.HTML
pagination_links @conn, @page, [], MyAppWeb.scrivener_config()

# MyOtherAppWeb.ex
def scrivener_config do
  Application.get_env(:my_other_app, :scrivener_html, [])
end

# In a view
import Scrivener.HTML
pagination_links @conn, @page, [], MyOtherAppWeb.scrivener_config()

One short function and one is no longer dependent on how scrivener_html does load config and it would work just as well if the issue is not two apps in an umbrella, but rather a “small width” pagination vs. a “wide” pagination.

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5

Thanks a lot for that explanation. I didn’t realise that scrivener_html “pagination_links/4” helper just takes as opts a keyword list that include exactly the available configuration keys for the package.