Don't read from configuration in compiletime macros

[commanded]

Don't read from configuration in compiletime macros

[slashdotdash]

Thanks for a the bug report. I'll test what happens when you force a recompile (mix compile --force) and add a note to the README if that solves the issue. It's unlikely that a user will swap event store providers more than once after initial setup. The macro provides convenient, and quick, access to the module.

[timbuchwaldt]

I think you could quote this code. It should be equally fast (as it will be evaluated at compiletime as well) but the expansion will happen at compiletime of the module that uses Commanded.EventStore. But thats guesswork now :D

[slashdotdash]

Yes, that's exactly what it should be doing. Thanks for the pointer, want to submit a pull request with the change ;-)

[timbuchwaldt]

I tried it locally, sadly my (poor) understanding of the macro system let to no improvement on this.

[slashdotdash]

That's a shame, not to worry though. I'll take a look.

[slashdotdash]

I've done some testing on this issue. It appears to be ok if you force a recompile of Commanded after making the config change.

To verify, I added logging to the Commanded.EventStore macro to output the configured adapter:

defmodule Commanded.EventStore do
  defmacro __using__(_) do
    adapter = Application.get_env(:commanded, :event_store_adapter) || raise ArgumentError, "Commanded expects :event_store_adapter to be configured in environment"
    IO.puts "event store adapter: #{inspect adapter}"

    quote do
      @event_store unquote(adapter)
    end
  end
end

Then I configured my app to use the in-memory adapter:

$ mix deps.compile commanded --force
==> commanded
Compiling 37 files (.ex)
event store adapter: Commanded.EventStore.Adapters.InMemory
...

I changed the config in my app to use the event store adapter and forced a recompile:

$ mix deps.compile commanded --force
==> commanded
Compiling 37 files (.ex)
event store adapter: Commanded.EventStore.Adapters.EventStore
...

So given that outcome, I've updated the README to include the above force recompile step when installing, or changing between, event store adapters.