Dialyzer message: "Function data/1 has no local return", when default_params is set

[ratbag98]

Using dataloader 1.3 on:

elixir -v
Erlang/OTP 21 [erts-10.0.4] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [hipe]

Elixir 1.6.6 (compiled with OTP 21)

When my data functions look like:

def data(default_params) do
  Dataloader.Ecto.new(Repo, query: &query/2, default_params: default_params)
end

Dialyzer complains with the "Function data/1 has no local return" message, which trickles up to its callers (terminating with the dataloader setup function).

If the code looks like:

def data(default_params) do
  Dataloader.Ecto.new(Repo, query: &query/2)
end

(ie no default_params), then I get no dialyzer warnings (at all, in a 310-file project, how did that happen?). Yay! Of course, I need the default params in order to pass auth information to the queries.

Looking in Dataloader.Ecto.new I see plenty of opportunities for things to go wrong, but I'm not convinced I can fix it before the heat-death of the universe. Any dialyzer gurus fancy taking a look?

Thanks, Rob.

[benwilson512]

This is probably because default_params isn't in the opt typespec, and it should be https://github.com/absinthe-graphql/dataloader/blob/master/lib/dataloader/ecto.ex#L163

I've added it to master, can you try running against master and seeing if that works?

{:dataloader, github: "absinthe-graphql/dataloader"}

[ratbag98]

That fixed it. Thanks for your customarily insanely rapid response. Seriously, take a break dude.

Side note: I actually tried making that change in my local copy before creating this issue, but I obviously didn't flush some dialyzer cache or did something equally stupid since it didn't do the trick for me.

[benwilson512]

Thanks for pointing it out!

[axelson]

@ratbag98 You probably needed to pass the --force-check option:

mix dialyzer --force-check

Here's the description of the option: "Force PLT check also if lock file is unchanged. Useful when dealing with local deps."