Mix.exs conditional code : application or included as a dependency

Questions / Help
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1

Is this in any way possible? I’m looking for the least hacky solution possible.

Project runs standalone (for hacking/testing) or as a dependency where you would get a shell on the running server and execute a processing run.

It’s open-source but I’d rather not get bogged down in the rationalle - is this possible?

I did have a snippet Keyword.get(Mix.Project.config(), :app) but it’s not working when placed in the mix.exs file

case Keyword.get(Mix.Project.config(), :app) do
      :ex_bench -> dependent_application()
      _ -> application(Mix.env())
    end

I mean, in fairness, it does say in the mix documentation :

Do not use Mix.Project.config/0 to find the runtime configuration. Use it only to configure aspects of your project (like compilation directories) and not your application runtime.

I don’t want to find the runtime configuration though, I just want to find out if the project is being compiled and run as a dependency or compiled and run as a standalone project and start the appropriate applications for each environment.

2

How is running standalone different from usage as dependency?

3

It starts up webserver, plug, prometheus, for metrics scraping - as a dependency it just communicates metrics via telemetry, I might even remove that requirement.

4

So what about explicitly using config to determine what to do instead of relying on mix internals, which shouldn‘t be used at runtime?

5

Are you sure these aren’t two distinct applications? One library and a “standalone” application that depends on the library?

6

Nah it’s for iterative testing - a developer convenience - running metrics endpoints etc, as a dependency it only assumes ExPrometheus will be available.

Take a look at the startup behaviour matrix - feedback welcome.

7

Is that for users of the library or you as the developer of the library?

8

I’m thinking both - run as a standalone app for plugin development, deploy as dependency when testing live services.