Sensible way to abstract away request client library in my application?

This looks okay. You can also use mox that basically does the same thing + has verifications/assertions you can use in tests.

Was just reading through mox documentation then. I’ll see how far I get in my tests.

Maybe examples here will make it a bit more clear: Mox

Not entirely sure how mox is working, but I have this:

defmodule Example do
  @callback function(integer()) :: integer()
  @callback another(integer()) :: integer()
end

Mox.defmock(ExampleMock, for: Example)

test "adheres to contract" do
  ExampleMock
  |> expect(:function, fn x -> x end)

  assert ExampleMock.function("string") == "string"
end

..passes. But my type specifies integer and I have another function defined in my @callback which hasn’t been defined in the ExampleMock (though those guarantees don’t appear to exist anyway when using @behaviour in derived modules). Are those types (integer(), etc) just for documentation purposes? They don’t have any effect beyond that?

Seems a shame to have all of this ceremony without the guarantees. Seem more like guidelines than explicit contracts?

I think they can be checked by dialyzer.

Ahh I see. I’ve not delved into that yet.

Yep, these are not checked by Elixir compiler, so serve as documentation only unless you use dialyzer.

Fair enough. I’d like to use dialyzer but that’s a whole can of worms I’m unwilling to open. Included it in a project and it’s coming up with all kinds of non-issues/noise, even with warnings disabled. Not enough time in the day to be fighting with another tool

@spec is good enough for me.

It is not that complicate to use dialyzer with dialyxir… just add

{:dialyxir, "~> 0.5.1", only: [:dev], runtime: false}

to your deps.

Then run (it take some time at first, but then it’s ok)

$ mix deps.get
$ mix dialyzer

I had to ignore some warnings coming from some Erlang sources included in my project. To configure this is also simple, just add to mix.exs, in the project section.

      dialyzer: [
        ignore_warnings: "dialyzer.ignore-warnings"
      ],

and create a file dialyzer.ignore-warnings containing the rules You want to ignore.

Yep, that’s what I tried.

I just can’t be doing with cryptic stuff like the following about code which works:

`

The pattern {'ok', Vresponse@1} can never match the type #{'__client__':=fun(), '__module__':=atom(), '__struct__':='Elixir.Tesla.Env', 'body':=_, 'headers':=#{binary()=>binary()}, 'method':='delete' | 'get' | 'head' | 'options' | 'patch' | 'post' | 'put' | 'trace', 'opts':=[any()], 'query':=[{atom() | binary(),binary() | [{atom() | binary(),binary() | [{_,_}]}]}], 'status':=integer(), 'url':=binary()}
`

Well it can match the type because it does. I would love to have this checking if it worked.

Also:

:0: Unknown function 'Elixir.GenStage':start_link/2 :0: Unknown function 'Elixir.Request':make/1 lib/gen_stage.ex:1: Callback info about the 'Elixir.GenStage' behaviour is not available

..and in my templates (using slime):

/templates/layout/app.html.slim:1: Guard test _@7::bitstring() =:= 'false' can never succeed